Sentinel-5 precursor/TROPOMI
Level 2 Product User Manual UV
Aerosol Index

document number: S5P-KNMI-L2-0026-MA

authors: Arnoud Apituley, Mattia Pedergnana, Maarten Sneep, J. Pepijn Veefkind, Diego Loyola,
Deborah Stein Zweers

CI identification: CI-7570-PUM

issue: 2.4.0

applicable to processor release : 2.4.0
date: 2022-07-11

status: released

S5P L2 PUM UV Aerosol Index
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S5P-KNMI-L2-0026-MA
Page 2 of 126

Document approval record
This document was prepared by Arnoud Apituley, Mattia Pedergnana, Maarten Sneep, J. Pepijn Veefkind,
Diego Loyola, Deborah Stein Zweers.

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Page 3 of 126

Document change record
issue

date

1.0.0

2018-06-13

itemcomments
Prepared and updated for public release of the UV aerosol index
dataproduct.

2.0.0

2021-06-24

Released with L2 processor update July 2021

2.0.1

2021-11-15

Updated for release 2.3.1 of the processor.

3.0.0

2022-07-11

Updated for release 2.4.0 of the processor.

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Contents
Document approval record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2Document change record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3

List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

1
1.1
1.2
1.3

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Purpose and objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Document overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5
5
5
5

2
2.1
2.2
2.3
2.4

Applicable and reference documents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Applicable documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standard documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reference documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electronic references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6
6
6
6
8

3
3.1
3.2

Terms, definitions and abbreviated terms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Terms and definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Acronyms and Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9
9
9

4
4.1

Overview of the Sentinel 5 precursor/TROPOMI Level 2 Products. . . . . . . . . . . . . . . . . . . . . .
File name convention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9
10

5
5.1

Data Distribution and Product Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Information to supply with a support request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10
10

6

General Reader and Visualisation Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11

7

Instrument description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11

8
8.1
8.2
8.3

S5p/TROPOMI L2 UV Aerosol Index Product Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Product Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Product Geophysical Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Using the S5p/TROPOMI L2 UV Aerosol Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13
13
13
13

9
9.1
9.2
9.3

General structure of S5P/TROPOMI Level 2 files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dimensions and dimension ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Time information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Geolocation, pixel corners and angles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16
18
18
19

10
10.1
10.1.1
10.2
10.2.110.2.210.2.3

Description of the aerosol index product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Group “PRODUCT” in “AER_AI” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Group “SUPPORT_DATA” in “PRODUCT” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Group “METADATA” in “AER_AI”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Group “QA_STATISTICS” in “METADATA” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Group “ALGORITHM_SETTINGS” in “METADATA” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Group “GRANULE_DESCRIPTION” in “METADATA” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21
24
30
52
53
68
72

11

Units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

103

12

Quality Assurance parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

104

13
13.1
13.2
13.3
13.4
13.5
13.6
13.7

Generic metadata and attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Climate and Forecast conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
NetCDF User Guide Conventions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Global attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ESA earth observation header . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inspire directive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ISO and OGC standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

114
114
115
115
115
116
116
116

A

Flag descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

118

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List of Tables
1
2
3
4
5
6
7
8
9
10
11
12
13

Standard S5P L2 products with name, identifier and responsible institutes . . . . . . . . . . . . . . . . . . .
Components of an S5P file name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reference times available in a S5P L2 file. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Quality assurance parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Abbreviations used in metadata descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Metadata in the fixed header required by the ESA earth observation file format standard . . .
Fields in the Validity_Period group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fields in the source group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
netCDF-4 type definitions and fill values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Attributes for variables used in S5p netCDF-4 files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Processing quality flags, errors, processing failures and filter conditions for S5P Level 2 . . . .
Processing quality flags, warnings for S5P Level 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Surface classification for S5P Level 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9
10
19
105
114
115
115
116
117
117
119
123
125

List of Figures
1
2
3
4
5
6
7
8

Panoply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TROPOMI measurement principle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Aerosol Index Example using the 340/380 wavelength pair. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Aerosol Index Example using the 354/388 wavelength pair. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Aerosol Index Example using the 340/380 wavelength pair (Zoom in). . . . . . . . . . . . . . . . . . . . . . . . .
Aerosol Index Example showing smoke plumes from individual fires. . . . . . . . . . . . . . . . . . . . . . . . . .
Graphical description of the generic structure of a Level 2 file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pixel corner coordinates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11
12
14
14
15
15
17
19

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1

Introduction

1.1

Identification

S5P-KNMI-L2-0026-MA
Page 6 of 126

This document, identified as S5P-KNMI-L2-0026-MA, describes the technical characteristics of the S5p/TROPOMI
Level 2 products that are needed for efficient and correct use of the data contained. This product user manualis specific for UV Aerosol Index.

1.2

Purpose and objective

The Sentinel-5 Precursor (S5p) mission is a low Earth orbit polar satellite system to provide information andservices on air quality, climate and the ozone layer. The S5p mission is part of the Global Monitoring of theEnvironment and Security (GMES/COPERNICUS) space component programme. The S5p mission consistsof a satellite bus, the payload consisting of the TROPOspheric Monitoring Instrument (TROPOMI), and aground system. A journal paper describing the mission and its objectives can be found in [RD1], while acomprehensive description of the mission can be found in [RD2]. Furthermore, various websites are maintainedwith S5p/TROPOMI information, e.g. [ER1, ER2].
From the data collected by the TROPOMI instrument, a number of geophysical (L2) products are derived.
The algorithms for the raw data treatment (L0 – L1b) and the actual L2 data processing are each described in
an algorithm theoretical basis document (ATBD). This Product User Manual (PUM) describes the technicalcharacteristics of the S5p/TROPOMI Level 2 geophysical data products that are needed for efficient and correct
use of the data contained.
In the PUM, the common structure of the datafiles and metadata used in all the delivered L2 products aswell as a specific section related to the UV Aerosol Index product are described.

1.3

Document overview

We start with a summary of the S5p L2 products and information needed to obtain and inspect data, as well
as how to obtain product support. The UV Aerosol Index data product is described next, with examples, andinformation about the use of the data. Format, L2 structure and metadata are addressed in the next chapter,followed by the detailed description of the UV Aerosol Index data. We then continue with a discussion of units
and quality assurance parameters. The final chapter contains information about generic metadata and the
Appendix lists measurement flags, processing quality flags, and surface classifications.

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2

Applicable and reference documents

2.1

Applicable documents

S5P-KNMI-L2-0026-MA
Page 7 of 126[AD1] Tailoring of the Earth Observation File Format Standard for the Sentinel 5 precursor Ground Segment.
source: ESA/ESTEC; ref: S5P-TN-ESA-GS-106; issue: 2.2; date: 2015-02-20.

2.2Standard documents
There are no standard documents

2.3

Reference documents[RD1] J. P. Veefkind, I. Aben, K. McMullan et al.; TROPOMI on the ESA Sentinel-5 Precursor: A GMES
mission for global observations of the atmospheric composition for climate, air quality and ozone layer
applications. Remote Sens. Environ.; 120 (2012), 70; 10.1016/j.rse.2011.09.027.
[RD2] Input/output data specification for the TROPOMI L01b data processor.
source: KNMI; ref: S5P-KNMI-L01B-0012-SD; issue: 10.0.0; date: 2019-07-19.
[RD3] S5P/TROPOMI ATBD Cloud Products.
source: DLR; ref: S5P-DLR-L2-ATBD-400I; issue: 2.3.0; date: 2021-06-25.
[RD4] Sentinel-5 precursor/TROPOMI Level 2 Product User Manual Cloud.
source: DLR; ref: S5P-L2-DLR-PUM-400I; issue: 2.4.0; date: 2022-07-11.
[RD5] S5P-NPP Cloud Processor ATBD.
source: RAL Space; ref: S5P-NPPC-RAL-ATBD-0001; issue: 1.0.0; date: 2016-02-12.
[RD6] S5P/TROPOMI HCHO ATBD.
source: BIRA; ref: S5P-BIRA-L2-400F-ATBD; issue: 2.4.1; date: 2022-06-22.
[RD7] Sentinel-5 precursor/TROPOMI Level 2 Product User Manual HCHO.
source: DLR; ref: S5P-L2-DLR-PUM-400F; issue: 2.4.0; date: 2022-07-11.
[RD8] S5P/TROPOMI SO2 ATBD.
source: BIRA; ref: S5P-BIRA-L2-400E-ATBD; issue: 2.4.0; date: 2022-06-22.
[RD9] Sentinel-5 precursor/TROPOMI Level 2 Product User Manual SO2 .
source: DLR; ref: S5P-L2-DLR-PUM-400E; issue: 2.4.0; date: 2022-07-11.
[RD10] S5P/TROPOMI Total ozone ATBD.
source: DLR; ref: S5P-L2-DLR-ATBD-400A; issue: 2.3.0; date: 2021-06-04.
[RD11] Sentinel-5 precursor/TROPOMI Level 2 Product User Manual Total Ozone Column.
source: DLR; ref: S5P-L2-DLR-PUM-400A; issue: 2.4.0; date: 2022-07-11.
[RD12] TROPOMI/S5P ATBD of tropospheric ozone data products.
source: DLR/IUP; ref: S5P-DLR-IUP-L2-400C; issue: 2.3.0; date: 2021-06-04.
[RD13] Sentinel-5 precursor/TROPOMI Level 2 Product User Manual Ozone Tropospheric Column.
source: DLR; ref: S5P-L2-DLR-PUM-400C; issue: 2.3.0; date: 2021-06-04.
[RD14] TROPOMI ATBD of the Aerosol Layer Height product.
source: KNMI; ref: S5P-KNMI-L2-0006-RP; issue: 2.4.0; date: 2022-04-08.
[RD15] Sentinel-5 precursor/TROPOMI Level 2 Product User Manual Aerosol Layer Height.
source: KNMI; ref: S5P-KNMI-L2-0022-MA; issue: 2.4.0; date: 2022-07-11.
[RD16] TROPOMI ATBD of the UV aerosol index.
source: KNMI; ref: S5P-KNMI-L2-0008-RP; issue: 2.0.0; date: 2021-07-05.

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Page 8 of 126[RD17] TROPOMI ATBD Ozone profile and tropospheric profile.
source: KNMI; ref: S5P-KNMI-L2-0004-RP; issue: 1.0.0; date: 2021-10-22.
[RD18] Sentinel-5 precursor/TROPOMI Level 2 Product User Manual Ozone Profile and Tropospheric Ozone
Profile.
source: KNMI; ref: S5P-KNMI-L2-0020-MA; issue: 2.4.0; date: 2022-07-11.
[RD19] TROPOMI ATBD of the total and tropospheric NO2 data products.
source: KNMI; ref: S5P-KNMI-L2-0005-RP; issue: 2.4.0; date: 2022-07-11.
[RD20] Sentinel-5 precursor/TROPOMI Level 2 Product User Manual Nitrogen Dioxide.
source: KNMI; ref: S5P-KNMI-L2-0021-MA; issue: 2.4.0; date: 2022-07-11.
[RD21] Algorithm Theoretical Baseline Document for Sentinel-5 Precursor: Carbon Monoxide Total Column
Retrieval.
source: SRON; ref: SRON-S5P-LEV2-RP-002; issue: 2.4.0; date: 2022-07-12.
[RD22] Sentinel-5 precursor/TROPOMI Level 2 Product User Manual Carbon Monoxide Column.
source: SRON/KNMI; ref: SRON-S5P-LEV2-MA-002; issue: 2.4.0; date: 2022-07.11.
[RD23] Algorithm Theoretical Baseline Document for Sentinel-5 Precursor methane retrieval.
source: SRON; ref: SRON-S5P-LEV2-RP-001; issue: 2.4.0; date: 2022-05-30.
[RD24] Sentinel-5 precursor/TROPOMI Level 2 Product User Manual Methane.
source: SRON/KNMI; ref: SRON-S5P-LEV2-MA-001; issue: 2.4.0; date: 2022-07-11.
[RD25] Tailoring of the Earth Observation File Format Standard for the Sentinel 5 precursor Ground Segment.
source: ESA/ESTEC; ref: S5P-TN-ESA-GS-106; issue: 2.2; date: 2015-02-20.
[RD26] Algorithm theoretical basis document for the TROPOMI L01b data processor.
source: KNMI; ref: S5P-KNMI-L01B-0009-SD; issue: 9.0.0; date: 2019-07-19.
[RD27] Earth Observation – Ground segment file format standard.
source: ESA/ESTEC; ref: PE-TN-ESA-GS-0001; issue: 2.0; date: 2012-05-03.
[RD28] Geographic information – Metadata.
source: ISO; ref: ISO 19115:2003(E); issue: 1; date: 2003-05-01.
[RD29] Geographic information – Metadata – Part 2: Extensions for imagery and gridded data.
source: ISO; ref: ISO 19115-2:2009(E); issue: 1; date: 2009-02-12.
[RD30] Geographic information – Data quality.
source: ISO; ref: ISO 19157; issue: 1; date: 2013-10-10.
[RD31] Earth Observation Metadata profile of Observations & Measurements.
source: Open Geospatial Consortium; ref: OGC 10-157r3; issue: 1.0; date: 2012-06-12.
[RD32] Data Standards Requirements for CCI Data Producers.
source: ESA; ref: CCI-PRGM-EOPS-TN-13-0009; issue: 1.1; date: 2013-05-24.
[RD33] Metadata specification for the TROPOMI L1b products.
source: KNMI; ref: S5P-KNMI-L01B-0014-SD; issue: 6.0.0; date: 2019-07-19.
[RD34] Data elements and interchange formats – Information interchange – Representation of dates andtimes.
source: ISO; ref: ISO 8601:2004(E); issue: 3; date: 2004-12-01.
[RD35] Wavelength calibration in the Sentinel 5-precursor Level 2 data processors.
source: KNMI; ref: S5P-KNMI-L2-0126-TN; issue: 1.0.0; date: 2015-09-11.
[RD36] M.L. Carroll, J.R. Townshend, C.M. DiMiceli et al.; A new global raster water mask at 250 m resolution.
International Journal of Digital Earth; 2 (2009) (4), 291; 10.1080/17538940902951401.
[RD37] Geographic information – Metadata – XML schema implementation.
source: ISO; ref: ISO 19139:2007(E); issue: 1; date: 2010-12-13.

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source: Open Geospatial Consortium; ref: OGC 10-025r1; issue: 2.0; date: 2011-03-22.
[RD39] Sentinel 5 precursor/TROPOMI KNMI and SRON level 2 Input Output Data Definition.
source: KNMI; ref: S5P-KNMI-L2-0009-SD; issue: 15.0; date: 2021-08-05.
[RD40] Sentinel-5 Precursor Level 2 UPAS Processor Input/Output Definition Document.
source: DLR-IMF; ref: S5P-L2-DLR-IODD-3002; issue: 3.3.0; date: 2017-06-01.
[RD41] S5P-NPP Cloud Processor IODD.
source: RAL; ref: S5P-NPPC-RAL-IODD-0001; issue: 0.10.0; date: 2014-05-28.
[RD42] John Caron; Annotated Schema for NcML (2011). URL http://www.unidata.ucar.edu/
software/netcdf/ncml/v2.2/AnnotatedSchema4.html.
[RD43] INSPIRE Metadata Regulation, Commission Regulation (EC), No1205/2008.
source: EC; ref: Commission Regulation (EC) No 1205/2008; date: 2008-12-03.
[RD44] INSPIRE Metadata Implementing Rules: Technical Guidelines based on EN ISO 19115 and EN ISO
19119.
source: EC JRC; ref: MD_IR_and_ISO_v1_2_20100616; issue: 1.2; date: 2010-06-16.
[RD45] Geographic Information – Observations and Measurements.
source: ISO; ref: ISO 19156:2011(E); date: 2011-12-20.
[RD46] Observations and Measurements - XML Implementation.
source: OGC; ref: OGC 10-025r1; issue: 2.0; date: 2011-03-22.

2.4

Electronic references[ER1] Tropomi official website. URL http://www.tropomi.eu.
[ER2] S5P official website.
sentinel-5p.

URL

https://sentinel.esa.int/web/sentinel/missions/[ER3] Robert B. Schmunk; Panoply netCDF, HDF and GRIB Data Viewer. URL http://www.giss.nasa.
gov/tools/panoply/.
[ER4] Infrastructure for Spatial Information in the European Community (INSPIRE) Directive 2007/2/EC. URL
http://inspire.jrc.ec.europa.eu/.
[ER5] Brian Eaton, Jonathan Gregory, Bob Drach et al.; NetCDF Climate and Forecast (CF) Metadata
Conventions. Lawrence Livermore National Laboratory (2014). Version 1.7 draft; URL http://
cfconventions.org.
[ER6] ESIP; Attribute Conventions for Dataset Discovery (ACDD). 1st edition (2013). URL http://wiki.
esipfed.org/index.php/Attribute_Convention_for_Data_Discovery_(ACDD).
[ER7] NetCDF Users Guide (2011). URL http://www.unidata.ucar.edu/software/netcdf/docs/
netcdf.html.
[ER8] USGS; Global Land Cover Characteristics Data Base Version 2.0 (2012). Website last visited on March
6, 2017; URL https://lta.cr.usgs.gov/glcc/globdoc2_0.
[ER9] The ECS SDP Toolkit (2012). DEM and land-sea mask data itself is available from ftp://
edhs1.gsfc.nasa.gov/edhs/sdptk/DEMdata; URL http://newsroom.gsfc.nasa.gov/
sdptoolkit/TKDownload.html.
[ER10] UDUNITS 2 Manual (2011). URL http://www.unidata.ucar.edu/software/udunits/.
[ER11] Cooperative Ocean/Atmosphere Research Data Service; Conventions for the standardization of
NetCDF files (1995). URL http://ferret.wrc.noaa.gov/noaa_coop/coop_cdf_profile.
html.

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Terms, definitions and abbreviated terms

Terms, definitions, and abbreviated terms that are specific for this document can be found below.

3.1

Terms and definitions

ATBD

Algorithm Theoretical Basis Document

TBA

To be Added

TBC

To be Confirmed

TBD

To be Defined

3.2

Acronyms and Abbreviations

ATBD

Algorithm Theoretical Basis Document

DLR

Deutsches Zentrum für Luft- und Raumfahrt

ESA

European Space Agency

KNMI

Koninklijk Nederlands Meteorologisch Instituut

IODD

Input Output Data Definition

OCRA

Optical Cloud Recognition Algorithm

PUM

Product User Manual

ROCINN

Retrieval of Cloud Information using Neural Networks

QA

Quality Assurance

UPAS

Universal Processor for UV/VIS Atmospheric Spectrometers

4

Overview of the Sentinel 5 precursor/TROPOMI Level 2 Products

The Sentinel 5 Precursor mission aims at providing information and services on air quality and climate in
the timeframe 2017–2023. The S5p mission is part of the Global Monitoring of the European Programme
for the establishment of a European capacity for Earth Observation (COPERNICUS). TROPOMI makes daily
global observations of key atmospheric constituents, including ozone, nitrogen dioxide, sulfur dioxide, carbon
monoxide, methane, formaldehyde as well as cloud and aerosol properties. The list of standard S5p/TROPOMI
L2 products is given in table 1. Other products, such as UV index, are under development and will madeavailable at a later date.
Table 1: Standard S5P L2 products with name, identifier, and responsible institutes.
Product

ATBD

PUM

Identifier

Institution

Cloud

[RD3]

[RD4]

L2__CLOUD_DLR

NPP-VIIRS Clouds

[RD5]

[RD5]

L2__NP_BDx

RAL

HCHO

[RD6]

[RD7]

L2__HCHO__

BIRA/DLR

SO2

[RD8]

[RD9]

L2__SO2___

BIRA/DLR

O3 Total Column[RD10][RD11]

L2__O3____

BIRA/DLRO3 Tropospheric Column[RD12][RD13]

L2__O3_TCL

IUP/DLR

Aerosol layer height[RD14][RD15]

L2__AER_LH

KNMI

Ultra violet aerosol index[RD16]

This document

L2__AER_AI

KNMI

O3 Full Profile[RD17][RD18]

L2__O3__PR

KNMI

NO2

[RD19][RD20]

L2__NO2___

KNMI

CO

[RD21][RD22]

L2__CO____

SRON/KNMI

CH4[RD23][RD24]

L2__CH4___

SRON/KNMI

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File name convention

The table specifies an identifier that is a substring of real name. The complete filename conventions for all theS5p products can be found in [RD25, chapter 4]. Note that intermediate L2 products beside those listed intable 1 may exist within the PDGS framework. For each of the products listed in the table, a PUM is available.
Note that product documentation, e.g. ATBDs and PUMs, will be updated with new releases of processors.
User documentation is distributed through the tropomi website [ER1]. Information about S5p mission can befound at the official ESA website for the Sentinel 5 precursor mission [ER2].
In the current PUM the UV Aerosol Index product is described and an example of the full real name is asfollowing:
S5P_NRTI_L2__AER_AI_20190920T054303_20190920T054803_10028_01_010302_20190920T062930.nc

The components of this file name are given in table 2
Table 2: Components of an S5P product file name. Components are separated by underscores, except for the
file extension at the end, which is separated by a period. Character indices start counting at 0, the end-index isa Python style index, it lists the first character not in the block.
Start

End

Length033Mission name, always “S5P”

4

8

4

Processing stream, one of “NRTI” (near real-time), “OFFL” (offline) or “RPRO”(reprocessing)

9

19

10

Product identifier, as listed in table 1

20

35

15

Start of granule in UTC as “YYYYMMDDTHHMMSS”. The “T” is a fixed character.

36

51

15

End of the granule in UTC as “YYYYMMDDTHHMMSS”. The “T” is a fixed character.

52

57

5

Orbit number

58

60

2

Collection number

61

67

6

Processor version number as “MMmmpp”, with “MM” the major version number, “mm”
the minor version number, and “pp” the patch level.

68

83

15

The time of processing for this granule in UTC as “YYYYMMDDTHHMMSS”. The “T”
is a fixed character.

84

86

2

The file name extension. All Sentinel 5 precursor files are netCDF-4 files and use
the extension “nc”

5

Meaning

Data Distribution and Product Support

The TROPOMI UV Aerosol Index product data are available from the Copernicus Open Data Hub https://scihub.copernicus.eu.
The access and use of any Copernicus Sentinel data available through the Sentinel Data Hub is governedby the Legal Notice on the use of Copernicus Sentinel Data and Service Information and is given here: https://sentinels.copernicus.eu/documents/247904/690755/Sentinel_Data_Legal_Notice.

5.1

Information to supply with a support request

We have been very careful in the preparation of the processors, the processing system, the data distribution
system and all other components that generate the level 2 products for the Sentinel 5 precursor mission. You
may encounter problems when reading the level 2 files despite our care, or you may not understand what wehave written in the product user manual or the ATBD. You can contact us through the earth observation help
desk operated by ESA at EOSupport@copernicus.esa.int. Please clearly indicate that you are requestingsupport for Sentinel 5 precursor (S5p) / TROPOMI mission.
If you are requesting technical support it is helpful to provide us with details of the file you are trying to read. The easiest way to do this is to provide a “dump” of the header of the file. This can begenerated using the “ncdump” tool provided with the netCDF-4 library. Only the header is required, so“ncdump -h FILE.nc > FILE.cdl” will provide us with all metadata in the file and help us pinpoint how
the file was produced. Here you replace FILE.nc with the actual file name on the command line.

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Figure 1: Panoply

If generating the header fails, please provide us with the exact original file name of the granule you aretrying to read, the exact error message you get and the exact version of the software you are using, including
the versions of netCDF-4 and HDF-5. Providing us with a checksum to verify file integrity can also speed up
our response.

6

General Reader and Visualisation Tools

For reading and visualising you may find Panoply [ER3] a useful tool. Panoply is a cross-platform applicationthat plots geo-gridded and other arrays from netCDF, HDF, GRIB, and other datasets, including the Sentinel 5
precursor Level 2 datafiles. With Panoply 4 you can:• Slice and plot geo-gridded latitude-longitude, latitude-vertical, longitude-vertical, or time-latitude arraysfrom larger multidimensional variables.
• Slice and plot "generic" 2D arrays from larger multidimensional variables.
• Slice 1D arrays from larger multidimensional variables and create line plots.
• Combine two geo-gridded arrays in one plot by differencing, summing or averaging.
• Plot lon-lat data on a global or regional map using any of over 100 map projections or make a zonal
average line plot.
• Overlay continent outlines or masks on lon-lat map plots.
• Use any of numerous color tables for the scale colorbar, or apply your own custom ACT, CPT, or RGB
color table.
• Save plots to disk GIF, JPEG, PNG or TIFF bitmap images or as PDF or PostScript graphics files.
• Export lon-lat map plots in KMZ format.
• Export animations as AVI or MOV video or as a collection of invididual frame images.

7

Instrument description

On 13 October 2017 the Copernicus Sentinel 5 Precursor (S5P), the first of the European Sentinel satellites
dedicated to monitoring of atmospheric composition, was launched. The mission objectives of S5P are toS5P L2 PUM UV Aerosol Index
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globally monitor air quality, climate and the ozone layer in the time period between 2017 and 2023. The
first 6 months of the mission were used for special observations to commission the satellite and the groundprocessing systems; the operational phase started in April of 2018.
The single payload of the S5P mission is TROPOspheric Monitoring Instrument (TROPOMI), which has
been developed by The Netherlands in cooperation with the European Space Agency (ESA). TROPOMI is anadir viewing shortwave spectrometer that measures in the UV-visible wavelength range (270 – 500 nm), thenear infrared (710 – 770 nm) and the shortwave infrared (2314 – 2382 nm).
The instrument uses passive remote sensing techniques to attain its objective by measuring at the topof the atmosphere the solar radiation reflected by and radiated from the Earth. The instrument operates ina push-broom configuration with a wide swath. Light from the entire swath is recorded simultaneously anddispersed onto two-dimensional imaging detectors: the position along the swath is projected onto one directionof the detectors, and the spectral information for each position is projected on the other direction.
The instrument images a strip of the Earth on a two dimensional detector for a period of approximately 1
second during which the satellite moves by about 7 km. This strip has dimensions of approximately 2600 km
in the direction across the track of the satellite and 7 km in the along-track direction. After the 1 second
measurement a new measurement is started thus the instrument scans the Earth as the satellite moves. The
two dimensions of the detector are used to detect the different ground pixels in the across track direction andfor the different wavelengths. The measurement principle of TROPOMI is shown in figure 2.

th)

w

av

el

en

gt
hs

across track (swaFlight direction~7 km(1 s flight)~2600 kmFigure 2: TROPOMI measurement principle.
On August 6th, 2019, the instrument settings of TROPOMI were changed. The nominal integration time
was reduced from 1080 ms to 840 ms. Before the change the pixel size is 7.2 × 3.6 km2 for bands 2 –6, (UVN)
7.2 × 7.2 km2 for bands 7 and 8 (SWIR), and 21.6 × 28.8 km2 for band 1 (deep UV), after co-addition in theflight direction. After the change in the settings, the pixel dimension in the flight direction is reduced. The newsizes become 5.6 × 3.6 km2 for bands 2 –6, 5.6 × 7.2 km2 for bands 7 and 8, and 28 × 28.8 km2 for band 1, after
co-addition in the flight direction.
For the UVN spectrometers about 20 million spectra are observed per day. With that resolution TROPOMI
is a major step forward compared to its predecessors OMI (Ozone Monitoring Instrument), SCIAMACHY(Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) and GOME-2 (Global Ozone
Monitoring Experiment-2). The spatial resolution is combined with a wide swath to allow for daily global
coverage. The TROPOMI/S5P geophysical (Level 2) operational data products are listed in section 4.
The S5P will fly in a so-called loose formation with the U.S. Suomi NPP (National Polar-orbiting Partnership)satellite. The primary objective for this formation flying is to use the high spatial resolution cloud observation
capabilities of the VIIRS instrument (Visible Infrared Imager Radiometer Suite). The temporal separation
between TROPOMI and VIIRS is less than 5 minutes, both having an equator crossing time near 13:30 local
solar time. This formation enables synergistic data products and scientific research potentials.
The spectral range is split over 4 different detectors. By design these detectors do not observe on the

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same geographic grid. Combining products that were derived from different detectors will require some careful
re-mapping to take care of this spatial mismatch.
More details on the TROPOMI instrument and the operational concepts can be found in the Level 0 to 1B
ATBD [RD26, parts I – III].

8

S5p/TROPOMI L2 UV Aerosol Index Product Description

The Aerosol Index (AI) is a well-established data product that has been calculated for several different satellite
instruments spanning a period of nearly 40 years. The Aerosol Index described here is called the UVAI since
it is based on spectral contrast in the ultraviolet (UV) spectral range for a given wavelength pair, where thedifference between observed and modelled reflectance results in a residual value. When this residual is
positive it indicates the presence of UV-absorbing aerosols, like dust and smoke (from both biomass burningand volcanic sources), and is often referred to as the Absorbing Aerosol Index (AAI). Unlike satellite-based
aerosol optical thickness measurements, AAI can also be calculated in the presence of clouds so that daily,
global coverage is possible. This is ideal for tracking the evolution of episodic aerosol plumes from dust
outbreaks, volcanic ash, and biomass burning. The relatively simple calculation of the Aerosol Index is basedon wavelength dependent changes in Rayleigh scattering in the UV spectral range where ozone absorption isvery small, i.e. wavelengths longer than about 340 nm. For a given wavelength pair a ratio is calculated frommeasured top of the atmosphere (TOA) reflectance and pre-calculated theoretical reflectance for a Rayleighscattering-only atmosphere and results in a residual value. Positive values of this residual indicate the presenceof UV-absorbing aerosol. The UVAI is dependent upon aerosol layer characteristics including aerosol optical
thickness, aerosol single scattering albedo, aerosol layer height (ALH), and the underlying surface albedo. TheUVAI is a robust calculation that is well proven based on years of data, where the major strengths include
speed of calculation, global coverage, ease of use, and the potential for creation of long-term climate data
records. To maintain heritage with the OMI mission and with other aerosol index data records, both the 354/388
nm and the 340/380 nm pairs are calculated and included in the S5P UVAI data product.

8.1

Data Product Examples

In figures 3 and 4 TROPOMI UV Aerosol Index global product examples are shown for both wavelength pairs(340/380 nm and 354/388 nm) on 2018-03-31. In figure 5 a zoom in is shown over northern Africa of a large
dust event the same day. In figure 6 a zoom in is shown over central Africa on 2017-11-10, showing the smoke
plumes of individual fires.

8.2

Product Geophysical Validation

In general, TROPOMI captures aerosol plumes originating from desert dust, biomass burning and volcanic
eruptions in great detail owing to its high spatial resolution and high signal-to-noise ratio. Comparison of
TROPOMI UVAI with other satellite-derived aerosol index data has been carried out with using data from OMI
and OMPS. Based on these initial comparisons, The values of TROPOMI are observed to be lower than OMI
and OMPS. It is known that the aerosol index is sensitive to small variations in the calibrated radiance which
can lead to offsets, also as compared to the aerosol index from other satellite datasets. These relative offsets
as compared to OMI and to OMPS are within the reported UVAI error of ± 1.0 index point as provided in the
TROPOMI data product.

8.3

Using the S5p/TROPOMI L2 UV Aerosol Index

The most important feature that data user should be aware of is sun glint. Glint yields high values of UVAI and
its effects can be removed by using UVAI data with qa-values greater than 0.8.

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Figure 3: Aerosol Index Example using the 340/380 wavelength pair from spectra observed on 2018-03-31.

Figure 4: Aerosol Index Example using the 354/388 wavelength pair from spectra observed on 2018-03-31.

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Figure 5: Aerosol Index Example using the 354/388 wavelength pair from spectra observed on 2018-03-31,
zoomed in over northern Africa and the Middle-East. The height of the figure is 6500 km, the width is 12 000 km.

Figure 6: A zoom in over central Africa on 2017-11-10, showing the smoke plumes of individual fires in the UV
aerosol index using the 340/380 nm wavelength pair. The height of the figure is 1300 km, the width is 2500 km.
Note the different colour scale.

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General structure of S5P/TROPOMI Level 2 files

This section gives an overview of the basic structure of all Sentinel 5 precursor level 2 files. In subsections 9.1 –9.3 and sections 11 – 13 some details are provided on the background of the structure of the level 2 files of
Sentinel 5 precursor. A complete description of the variables in the UV Aerosol Index files is given in section 10.
Figure 7 gives a graphical representation of the generic structure of a TROPOMI Level 2 file. The outermost
layer is the file itself. Within the file different groups are used to organise the data and make it easier to findwhat you are looking for. Within the file there are two groups: “PRODUCT” and “METADATA”. Both of thesegroups contain sub-groups. The purpose of each group are discussed below.
PRODUCT The variables in this group will answer the questions what, when, where and how well. This
group stores the main data fields of the product, including the precision of the main parameters, latitude,
longitude and variable to determine the observation time and the dimensions needed for the data (a timereference dimension (time), the number of measurements in the granule (scanline), the number of spectra
in a measurement (ground_pixel) and depending on the product also a pressure-level dimension, orstate-vector dimensions). The “qa_value” parameter summarizes the processing flags into a continuous
value, giving a quality percentage: 100 % is the most optimal value, 0 % is a processing failure, in
between lies a continuum of values1 .
In the ‘PRODUCT’ group a sub-group ‘SUPPORT_DATA’ can be found:
SUPPORT_DATA Additional data that is not directly needed for using and understanding the main data
product is stored in sub-groups of this group.
The data in this group is further split up into the following sub groups:
GEOLOCATIONS Additional geolocation and geometry related fields, including the pixel boundaries (pixel corners), viewing- and solar zenith angles, azimuth angles, and spacecraft location.
DETAILED_RESULTS Additional output, including state-vector elements that are not the main
parameter(s), output describing the quality of the retrieval result, such as a χ 2 value, anddetailed processing flags.
INPUT_DATA Additional input data, such as meteorological input data, surface albedo values,
surface altitude and other data that was used to derive the output. Note that input profile
information is not stored here, but is available for download from elsewhere.
METADATA This is a group to collect metadata items, such as the items that appear in the header file [RD27,
section 7] and items required by INSPIRE [ER4], ISO 19115 [RD28], ISO 19115-2 [RD29], ISO 19157 [RD30]
and OGC 10-157r3 [RD31]. These metadata standards are all meant to facilitate dataset discovery.
The metadata will be stored as attributes, while grouping attributes that belong to a specific standard
will be done by using sub-groups in the Metadata group. Some attributes are required to be attached to
the global level by convention, such as the CF metadata conventions [ER5], the Attribute Convention
for Dataset Discovery [ER6], the NetCDF-4 user guide [ER7] and the ESA CCI project [RD32]. Forinteroperability reasons the conventions are followed, and the specified global attributes are added to the
output files at the root-level.
ALGORITHM_SETTINGS An attribute is added to this group for each key in the configuration file. The
exact contents differ for each processor.
GRANULE_DESCRIPTION Parameters describing the granule, such as an outline of the geolocations
covered in the granule, the time coverage, and processing facility.
QA_STATISTICS Quality assurance statistics. This group contains two types of data:
1. The total number of pixel matching a certain criterion: number of input pixels, number of pixels
successfully processed and the number of pixels that failed for specific reasons. Also part ofthe pixel counting are the number of warnings that were raised, including those for the south
Atlantic anomaly, sun glint and solar eclipse. This is collectively known as ‘event counting’.
2. Histogram(s) of the main parameter(s) in the file. Histograms are additive and allow for easy
monitoring of changes over time. This can be a valuable addition for quality monitoring of thescience data.
ESA_METADATA The metadata items that are required in the ESA header.
ISO_METADATA The ISO metadata items, organized in subgroups.
1

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Sentinel 5P Level 2 product

Global attributes

PRODUCT
main

precision

qa_valuelatitudelongitudedelta_time

scanlineground_pixel

time

…

…

SUPPORT_DATAGEOLOCATIONSSZA…

DETAILED_RESULTS

processing_quality_flags

INPUT_DATA

surface_pressure…
…

METADATAALGORITHM_SETTINGS

Attributes

GRANULE_DESCRIPTION

Attributes

QA_STATISTICS

Attributes
Histogram_axis

Histogram

ESA_METADATA
ISO_METADATA

Attributes
Attributes and sub-groups

LegendRoot level

First level group

Second level group

Third level group

Variable

Attributes

Dimension
Figure 7: Graphical description of the generic structure of a Level 2 file. The elements labelled as a dimension
are coordinate variables. See section 9 for a full description.

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EOP_METADATA The EOP metadata items, organized in subgroups.
The work of Level 1B on metadata as described in the metadata specification for TROPOMI L01b
data processor [RD33] is used as the basis for the level 2 metadata, in particular for the items in the‘ISO_METADATA’ and ‘EOP_METADATA’ subgroups. The listed metadata standards give a data modeland an implementation guideline for producing an XML file with the metadata – as a side-file to thedata-file itself. The Level 1B IODS [RD2] describes a method to store the metadata in the NetCDF-4 file,and produce XML side-files as needed. A detailed discussion on metadata as it applies to Level 2 canbe found in section 13.
Details of the specific format of the level 2 product file for the UV Aerosol Index product is given in section 10.
Here all variables are described in detail.

9.1

Dimensions and dimension ordering

All variables in a NetCDF-4 file use named and shared dimensions. This explicitly connects variables todimensions, and to each other. A few of the dimension names were already shown in figure 7.
time A time dimension. The length of this dimension is 1, at least for S5P. The reason this dimension is used
are compatibility with Level 1B, and forward compatibility with Sentinel 4 and Level 3 output. Details areprovided in sections 9.2.
scanline The dimension that indicates the flight direction.
ground_pixel The dimension perpendicular to the flight direction.
Other dimensions can be added as needed, but these names shall be the default for these roles.
The climate and forecast metadata conventions recommend a specific order for dimensions in a variable [ER5, section 2.4]. Spatiotemporal dimensions should appear in the relative order: “date or time” (T ),“height or depth” (Z ), “latitude” (Y ), and “longitude” (X ). Note that the ordering of the dimensions in CDL, ourdocumentation and C/C++ is row-major: the last dimension is stored contiguously in memory2 .
Using straight latitude and longitude is fine with model parameters, but the S5P/TROPOMI Level 1B/Level 2
observation grid is not a regular grid. Because of the polar orbit, the across track dimension (‘ground_pixel’)
corresponds most closely with the longitude, and therefore is associated with the X -dimension, while thealong track dimensions (‘scanline’) corresponds most directly with latitude, and is therefore labelled as the
Y -dimension.
However, in the CF conventions goes on to recommend that additional dimensions are added before the(T, Z,Y, X) axes, that is to have contiguous (T, Z,Y, X) hyperslabs, and spread out the data in other dimensions.
We do not follow this recommendation. Instead we recommend to keep units that are likely to be accessed asa unit together in memory, but following the recommended order for (T,Y, X). Note that we do not follow the CF
conventions for profiles as they are more likely accessed as complete profiles rather than horizontal slices. A
few examples will help:
Tropospheric NO2 column This variable contains a single value per ground pixel, and the dimensions are(time, scanline, ground_pixel).
The state_vector_length variable that accompanies the state_vector_length dimension is a string array,giving the names of the state vector elements.

9.2

Time information

Time information is stored in two steps. We have the time dimension, which indicates the reference time. Thisreference time is defined to be UTC midnight before the start of the orbit, which itself is defined by spacecraft
midnight. The time variable contains the reference time in seconds since 2010-01-01, UTC midnight.
Alternative representations of the reference time are listed in table 3. The offset of individual measurements
within the granule is given in milliseconds with respect to this reference time in the variable delta_time.
The reason for this double reference is to more closely follow the CF conventions. Because the flight
direction relates the latitude and the time within the orbit, we have Y and T dimensions that are closely related.
2

Fortran uses column-major order, effectively reversing the dimensions in the code compared to the documentation.

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By separating these into a time dimension of length 1 and a scanline dimension, we obtain independent Y
and T dimensions. The actual observation time of an individual observation must be reconstructed from an
offset and a time-delta.
As a service to the users, the time is also stored in the ‘time_utc’ variable. This variable is a string array,with each observation time stored as an ISO date string [RD34].
Table 3: Reference times available in a S5P L2 file. Types: (A) global attribute, (D) dimensional variable, (V)variable. All reference times ignore leap seconds.
Name

Type

Description

time_reference(A)

ISO date/time string [RD34]

time_reference_days_since_1950(A)

The number of days since January first, 1950, UTC midnight, as used in several weather and climate models(ECMWF, TM5).

time_reference_julian_day(A)

The Julian date of the reference time as used in astronomy.
This is the reference time system as used in IDL.

time_reference_seconds_since_1970(A)

The number of seconds since January first, 1970, UTC
midnight. This is also known as the unix epoch. Timefunctions on many systems will accept this number.

time

(D)

This variable contains the number of seconds since 201001-01, UTC midnight.

time_utc(V)

Array of ISO date/time strings [RD34], one for each observation, i.e. one for each element in the scanline dimension

9.3

Geolocation, pixel corners and angles

The latitude, longitude, pixel corner coordinates and related angles and satellite position in the level 2 files arecopied from the level 1B input data [RD26, chapters 26 and 27]. Details about the definitions can be foundthere. Note that the latitude and longitude have not been corrected for the local surface altitude, but are instead
given at the intersection of the line of sight with the WGS84 ellipsoid.
The geo-coordinates of the pixel corners are shown in Figure 8. Note that this choice follows the CF
metadata standard [ER5, section 7.1].

3

2)
1, i-1
= (j+

1
= (j+

, i+1

)

Fligh
n
ectio
t dir

(j, i)

0=

(j-1,

i-1)

(j1=

1)

1, i+

Figure 8: Pixel corner coordinates. The sequence {0, 1, 2, 3} refers to the elements in the corner dimension.
The azimuth angles, i.e. the solar azimuth angle ϕ0 and the viewing azimuth angle ϕ give the angle ofthe sun and the instrument respectively at the intersection of the line of sight with the WGS84 ellipsoid. Bothangles are given as degrees east relative to the local north. This definition is identical to the definition of
the azimuth angles in both the OMI and GOME-2 instruments, but requires some care when comparing to a

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radiative transfer model. A radiative transfer model will typically use ϕ − ϕ0 which differs by 180◦ as it follows
the path of the light.

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Description of the aerosol index product

Description of the main output file for the aerosol index product from the TROPOMI instrument on the Sentinel
5-precursor mission.
These are the file-level attributes.
If the ECMWF dynamic auxiliary data is not available a fallback solution will be used. In this case theLevel 2 output file will be flagged using the “Status_MET_2D” global attribute.

Global attributes in AER_AI
Group attributes attached to AER_AI
Name

Value

Type

Conventions‘CF-1.7’ (static)

NC_STRING

Name of the conventions followed by the dataset. Note that while we try to follow the climate and forecast
metadata conventions, there are some features – notably the use of groups to hierarchicaly organize thedata – that are not part of version 1.6 of the CF metadata conventions. In those cases we try to follow thespirit of the conventions. This attribute originates from the NUG standard.
institution‘%(institute)s’ (dynamic)

NC_STRING

The institute where the original data was produced. The actual processing center is given in theProcessingCenter attribute, here we would like to indicate the responsible parties. The value is acombination from BIRA, DLR, ESA, FMI, IUP, KNMI, MPIC, SRON, . . . . The actual value is a combinationof the ATBD institute and the institute that developed the processor. This attribute originates from the NUG
standard.
source‘Sentinel 5 precursor, TROPOMI, space-borne remotesensing, L2’ (dynamic)

NC_STRING

Method of production of the original data. Value includes instrument, generic description of retrieval, productlevel, and adds a short product name and processor version. This attribute originates from the CF standard.
history

NC_STRING

Provides an audit trail for modifications to the original data. Well-behaved generic netCDF filters willautomatically append their name and the parameters with which they were invoked to the global history
attribute of an input netCDF file. Each line shall begin with a timestamp indicating the date and time of day
that the program was executed. This attribute originates from the NUG, CF standards.
summary

NC_STRING

Miscellaneous information about the data or methods used to produce it.
If processing in a degraded mode occured, then a note should be placed in this attribute. A degraded
processing mode can occur for several reasons, for instance the use of static backup data for nominallydynamic input or an irradiance product that is older than a few days. A machine-parseable description isavailable in the “processing_status” attribute. This attribute originates from the CF standard.
tracking_id

NC_STRING

This unique tracking ID is proposed by the Climate Change Initiative – European Space Agency project.
This ID is a UUID and allows files to be referenced, and linked up to processing description, input data,
documentation, etc. The CCI-ESA project uses version 4 UUIDs (random number based) for consistency
with CMIP5. This attribute originates from the CCI standard.
id‘%(logical_filename)s’ (dynamic)

NC_STRING

The “id” and “naming_authority” attributes are intended to provide a globally unique identification for eachdataset. The “id” value should attempt to uniquely identify the dataset. The naming authority allows a further
refinement of the “id”. The combination of the two should be globally unique for all time. We use the logicalfile name for the “id” attribute. This attribute originates from the CCI standard.
time_reference‘YYYY-MM-DDT00:00:00Z’ (dynamic)

NC_STRING

UTC time reference as an ISO 8601 [RD34] string. This corresponds to the UTC value in the time
dimensional variable. By definition it indicates UTC midnight before the start of the granule.
time_reference_days_since_1950

0 (dynamic)

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The reference time expressed as the number of days since 1950-01-01. This is the reference time unit usedby both TM5 and ECMWF.
time_reference_julian_day

0.0 (dynamic)

NC_DOUBLE

The reference time expressed as a Julian day number.
time_reference_seconds_since_1970

0 (dynamic)

NC_INT64

The reference time expressed as the number of seconds since 1970-01-01 00:00:00 UTC. This is thereference time unit used by Unix systems.
time_coverage_start‘YYYY-MM-DDTHH:MM:SS.mmmmmmZ’ (dynamic)

NC_STRING

Start of the data granule in UTC as an ISO 8601 [RD34] string. See the discussion of the time_deltavariable on page 27 for details.
time_coverage_end‘YYYY-MM-DDTHH:MM:SS.mmmmmmZ’ (dynamic)

NC_STRING

End of the data granule in UTC as an ISO 8601 [RD34] string. See the discussion of the time_deltavariable on page 27 for details.
time_coverage_duration

NC_STRING

Duration of the data granule as an ISO 8601 [RD34] duration string (“PT%(duration_seconds)sS”). This
attribute originates from the CCI standard.
time_coverage_resolution

NC_STRING

Interval between measurements in the data granule as an ISO 8601 [RD34] duration string (“PT%(interval_seconds)fS”). For most products this is 1080 ms in nominal operation, except for “L2__O3__PR”, whichuses 3240 ms due to coaddition. This attribute originates from the CCI standard.
orbit

0 (dynamic)

NC_INT

The absolute orbit number, starting at 1 – first ascending node crossing after spacecraft separation. For
pre-launch testing this value should be set to “−1”.
references‘%(references)s’ (static)

NC_STRING

References that describe the data or methods used to produce it. This attribute originates from the CF
standard.
processor_version‘%(version)s’ (dynamic)

NC_STRING

The version of the data processor, as string of the form “major.minor.patch”.
keywords_vocabulary‘AGU index terms, http://publications.agu.org/authorresource-center/index-terms/’ (static)

NC_STRING

The guidelines followed for the keywords attribute. We use the index terms published by the AGU.
keywords‘%(keywords_agu)s’ (dynamic)

NC_STRING

Keywords from the “keywords_vocabulary” describing the contents of the file. To be provided by the
ATBD authors.
standard_name_vocabulary‘NetCDF Climate and Forecast Metadata Conventions
Standard Name Table (v29, 08 July 2015), http://
cfconventions.org/standard-names.html’ (static)

NC_STRING

The table followed for the standard_name attributes.
naming_authority‘%(naming_authority)s’ (dynamic)

NC_STRING

Specify who is giving out the id attribute. This attribute originates from the CCI standard.
cdm_data_type‘Swath’ (static)

NC_STRING

The THREDDS data type appropriate for this dataset, fixed to “Swath” for S5P level 2 products. This
attribute originates from the CCI standard.
date_created‘YYYY-mm-ddTHH:MM:SS.ffffffZ’ (dynamic)

NC_STRING

The date on which this file was created. This attribute originates from the CCI standard.
creator_name‘%(credit)s’ (dynamic)

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The name of the creator, equal to the value of the “gmd:credit” attribute. For S5P this attribute is set
to “The Sentinel 5 Precursor TROPOMI Level 2 products are developed with funding from the European
Space Agency (ESA), the Netherlands Space Office (NSO), the Belgian Science Policy Office, the German
Aerospace Center (DLR) and the Bayerisches Staatsministerium für Wirtschaft und Medien, Energie undTechnologie (StMWi).” This attribute originates from the CCI standard.
creator_url‘%(creator_url)s’ (dynamic)

NC_STRING

Hyperlink to a location where more information on the product can be found. Set to http://www.tropomi.
eu/. This attribute originates from the CCI standard.
creator_email‘EOSupport@Copernicus.esa.int’ (dynamic)

NC_STRING

Point of contact for more information and support for this product.
“mailto:EOSupport@Copernicus.esa.int”. This attribute originates from the CCI standard.
project‘Sentinel 5 precursor/TROPOMI’ (dynamic)

Set

to

NC_STRING

The name of the scientific project that created the data. This attribute originates from the CCI standard.
geospatial_lat_min

NC_FLOAT

Lowest latitude present in the file in decimal degrees. This attribute originates from the CCI standard.
geospatial_lat_max

NC_FLOAT

Highest latitude present in the file in decimal degrees. This attribute originates from the CCI standard.
geospatial_lon_min

NC_FLOAT

Lowest longitude present in the file in decimal degrees. This attribute originates from the CCI standard.
geospatial_lon_max

NC_FLOAT

Highest longitude present in the file in decimal degrees. This attribute originates from the CCI standard.
license‘No conditions apply’ (static)

NC_STRING

describe the restrictions to data access and distribution. For S5P “No conditions apply”. This attributeoriginates from the CCI standard.
platform‘S5P’ (static)

NC_STRING

Name of the satellite, set to “S5P”. This attribute originates from the CCI standard.
sensor‘TROPOMI’ (static)

NC_STRING

Name of the sensor, set to “TROPOMI”. This attribute originates from the CCI standard.
spatial_resolution

NC_STRING
2

Spatial resolution at nadir. For most products this is “3.5 × 7 km ”, except for “L2__O3__PR”, which uses
“28 × 21 km2 ” and “L2__CO____” and “L2__CH4___”, which both use “7 × 7 km2 ”. This attribute originatesfrom the CCI standard.
cpp_compiler_version

NC_STRING

The version of the compiler used for the C++ code. The value of this attribute is set via the Makefile.
cpp_compiler_flags

NC_STRING

The compiler flags passed to the C++ compiler. The value of this attribute is set via the Makefile.
f90_compiler_version

NC_STRING

The version of the compiler version used for the Fortran code. The value of this attribute is set via theMakefile. Note that not all processors make use of Fortran code.
f90_compiler_flags

NC_STRING

The compiler flags passed to the Fortran compiler. The value of this attribute is set via the Makefile. Notethat not all processors make use of Fortran code.
build_date

NC_STRING

The date on which the processor was built.
revision_control_identifier‘%(revision_control_source_identifier)s’ (dynamic)

NC_STRING

Revision control system identifier for the source used to build this processor.
geolocation_grid_from_band

NC_INT

The band from which the geolocation was taken, useful for colocating the level 2 output with other products.
identifier_product_doi‘%(product_doi)s’ (dynamic)

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This is the DOI (“Digital Object Identifier”) of the current product. It allows to easily find download andbackground information, even if that location is moved after the file has been created.
identifier_product_doi_authority‘http://dx.doi.org/’ (static)

NC_STRING

This attribute defines the authoritative service for use with DOI values in resolving to the URL location.
algorithm_version‘%(algorithm_version)s’ (dynamic)

NC_STRING

The algorithm version, separate from the processor (framework) version, to accomodate different release
schedules for different products.
title‘TROPOMI/S5P Aerosol Index %s L2 Swath %sx%skm’(dynamic)

NC_STRING

This is a short description of the product. In near-realtime processing the granule is shorter than 1 orbit,
and this attribute must be adapted accordingly. The nominal title is “TROPOMI/S5P Aerosol Index 1-Orbit
L2 Swath yx3.5km”, with the y dimension adjusted according to the spatial sampling of the input (7.0 or 5.5).
This attribute originates from the NUG standard.
product_version‘1.3.0’ (dynamic)

NC_STRING

Included for compatibility with the CCI project, where this item is defined as “the product version of this data
file.” We will use the file format version for this attribute following several CCI sub-projects. This attributeoriginates from the CCI standard.
processing_status‘Nominal’ (dynamic)

NC_STRING

Description the processing status of the granule on a global level, mainly based on the availability of auxiliary
input data.
Possible values: Nominal, Degraded
Status_MET_2D

NC_STRING

The status of ECMWF input, either “Nominal” or “Fallback”. Note that the “MET_2D” auxiliary input is used
as an achor point for all meteorological data (where applicable).
Possible values: Nominal, Fallback

10.1

Group “PRODUCT” in “AER_AI”

This is the main group containing the aerosol index product. At this level the dimensions and the main data
fields are defined. Support data can be found in the “SUPPORT_DATA” group.
The dimensions that are common to all products. These are all located in the “PRODUCT” group, andcan be accessed from that group and all sub-groups of the “PRODUCT” group, that is everywhere except the“METADATA” group.
All dimensions have an associated variable. These variables give a meaning to the dimension, spanning
the axis of other variables.
The latitude and longitude. Used in all products, placed in the “PRODUCT” group.
Dimensions in AER_AI/PRODUCT
scanline The number of measurements along the swath, in the flight-direction.
size Unlimited.
ground_pixel The number of ground pixels across track. This depends on the product and will follow thedimension found in the main input Level 1B product.
size -1 (dynamic)
source L1B.
corner The number of corners for a pixel.
size 4 (fixed)
time The time dimension. See the discussion of the associated dimensional variable on page 25 for details.
size 1 (fixed)
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scanline in AER_AI/PRODUCTDescription:

The coordinate variable scanline refers to the along-track dimension of the measurement.
The scanlines are time-ordered, meaning that “earlier” measurements have a lower index
than “later” measurements. This variable merely contains an index to ensure that whenindicating a pixel in a file the same index is used. This avoids the off-by-one confusion thatfrequently occurred in OMI discussions.

Dimensions:scanline (coordinate variable).

Type:

NC_INT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

Dimensionless, no physical quantity. This attribute originates from the CF standard.
axis‘Y’ (static)

NC_STRING

long_name‘along-track dimension index’ (static)

NC_STRING

comment‘This coordinate variable defines the indices along
track; index starts at 0’ (static)

NC_STRING

ground_pixel in AER_AI/PRODUCTDescription:

The coordinate variable ground_pixel refers to the across-track dimension of the measurement. The ground_pixel ordering is from left to right with respect to the flight direction.
For the Sentinel 5 precursor orbit this corresponds to west to east during the ascending
part of the orbit, i.e. a higher index corresponds to a higher longitude. This variable merely
contains an index to ensure that when indicating a pixel in a file the same index is used.
This avoids the off-by-one confusion that frequently occurred in OMI discussions.

Dimensions:

ground_pixel (coordinate variable).

Type:

NC_INT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

Dimensionless, no physical quantity. This attribute originates from the CF standard.
axis‘X’ (static)

long_name‘across-track dimension index’ (static)

NC_STRING

comment‘This coordinate variable defines the indices acrosstrack, from west to east; index starts at 0’ (static)

NC_STRING

NC_STRING

time in AER_AI/PRODUCTDescription:

The variable time(time) is the reference time of the measurements. The referencetime is set to YYYY-MM-DDT00:00:00 UTC, midnight UTC before spacecraft midnight, theformal start of the current orbit. The delta_time(scanline) variable indicates the timedifference of the observations with the reference time. Thus combining the informationof time(time) and delta_time(scanline) yields the measurement time for eachscanline as UTC time. The reference time(time) corresponds to the global attribute
time_reference which is specified as a UTC time specified as an ISO 8601 [RD34] date.

Dimensions:time (coordinate variable).

Type:

NC_INT.

Source:Processor.

Attributes:

Name

Value

units

‘seconds since 2010-01-01 00:00:00’ (dynamic)

NC_STRING

standard_name‘time’ (static)

NC_STRING

axis‘T’ (static)

NC_STRING

long_name‘reference time for the measurements’ (static)

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the time_reference global attribute’ (static)

NC_STRING

corner in AER_AI/PRODUCTDescription:

An index for the pixel corners. We follow the CF-Metadata conventions [ER5, section 7.1].
The full coordinate system is right-handed, and the order of the pixel corners is counterclockwise, starting in the “lower-left” corner (i.e. the smallest value in both latitude andlongitude on the ascending part of the orbit, or equivalently for TROPOMI the lowest value forboth the ground_pixel and scanline indices). See figure 8 on page 19 for a graphicaldepiction of the corners.

Dimensions:corner (coordinate variable).

Type:

NC_INT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

Dimensionless, no physical quantity. This attribute originates from the CF standard.
long_name‘pixel corner index’ (static)

NC_STRING

comment‘This coordinate variable defines the indices for the
pixel corners; index starts at 0 (counter-clockwise,starting from south-western corner of the pixel inascending part of the orbit)’ (static)

NC_STRING

latitude in AER_AI/PRODUCTDescription:

The latitude of the pixel centers of the ground pixels in the data. Latitude, longitude
coordinates for the ground pixel center and the ground pixel corners are calculated at the
WGS84 ellipsoid.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘pixel center latitude’ (static)

NC_STRING

units‘degrees_north’ (static)

NC_STRING

standard_name‘latitude’ (static)

NC_STRING

valid_min-90.0 (static)

NC_FLOAT

valid_max

90.0 (static)

NC_FLOAT

bounds‘/PRODUCT/SUPPORT_DATA/GEOLOCATIONS/
latitude_bounds’ (static)

NC_STRING

A link to the boundary coordinates, i.e. the pixel corners. Note that the use of group-namesin this attribute is an extension of the climate and forecasting metadata conventions.
longitude in AER_AI/PRODUCTDescription:

The longitude of the pixel centers of the ground pixels in the data. Latitude, longitude
coordinates for the ground pixel center and the ground pixel corners are calculated at the
WGS84 ellipsoid.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘pixel center longitude’ (static)

NC_STRING

units‘degrees_east’ (static)

NC_STRING

standard_name‘longitude’ (static)

NC_STRING

valid_min-180.0 (static)

NC_FLOAT

valid_max

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longitude_bounds’ (static)

NC_STRING

A link to the boundary coordinates, i.e. the pixel corners. Note that the use of group-namesin this attribute is an extension of the climate and forecasting metadata conventions.
delta_time in AER_AI/PRODUCTDescription:

The delta_time(scanline) variable indicates the time difference with the referencetime time(time) (see page 25). Thus combining the information of time(time) anddelta_time(scanline) yields the start of the measurement time for each scanline as
TAI2010 time. Combining the information in the global attribute time_reference withdelta_time(scanline) yields the start of the measurement time in UTC time. The UTC
time derived for the first scanline corresponds to the global attribute time_coverage_start. However, the UTC time derived for the last scanline does not correspond to
global attribute time_coverage_end. One scanline measurement is the result of adding
independent measurements during one coaddition period. The scanline measurement isgiven the measurement time of the first sample in this co-addition. It is the measurement
time of the last sample in the coaddition period of the last scanline that corresponds totime_coverage_end.
This variable gives the time offset in ms accuracy.

Dimensions:time, scanline.

Type:

NC_INT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘offset of start time of measurement relative totime_reference’ (static)

NC_STRING

units‘milliseconds’ (static)

NC_STRING

time_utc in AER_AI/PRODUCTDescription:

The time of observation expressed as ISO 8601 [RD34] date-time string.

Dimensions:time, scanline.

Type:

NC_STRING.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘Time of observation as ISO 8601 date-time string’(static)

NC_STRING

qa_value in AER_AI/PRODUCTDescription:

A continuous quality descriptor, varying between 0 (no data) and 1 (full quality data). The
value will change based on observation conditions and retrieval flags. Detailed quality flags
are provided in the processing_quality_flags elsewhere in the product.

Dimensions:time, scanline, ground_pixel.

Type:

NC_UBYTE.

Source:Processor.

Attributes:

Name

Value

units

‘1’ (static)

NC_STRING

scale_factor

0.01 (static)

NC_FLOAT

add_offset

0 (static)

NC_FLOAT

valid_min

0 (static)

NC_UBYTE

valid_max

100 (static)

NC_UBYTE

long_name‘data quality value’ (static)

NC_STRING

comment‘A continuous quality descriptor, varying between 0(no data) and 1 (full quality data). Recommend toignore data with qa_value < 0.5’ (static)

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NC_STRING

aerosol_index_354_388 in AER_AI/PRODUCTDescription:

The main output of the Aerosol Index retrieval algorithm (at wavelengths 354/388, i.e. theOMI pair).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

proposed_standard_name‘ultraviolet_aerosol_index’ (static)

NC_STRING

comment‘Aerosol index from 388 and 354 nm’ (static)

NC_STRING

long_name‘Aerosol index from 388 and 354 nm’ (static)

NC_STRING

radiation_wavelength354.0, 388.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index.
coordinates‘longitude latitude’ (static)

NC_STRING

ancillary_variables‘aerosol_index_354_388_precision’ (static)

NC_STRING

aerosol_index_340_380 in AER_AI/PRODUCTDescription:

The main output of the Aerosol Index retrieval algorithm (at wavelengths 340/380, i.e. theTOMS pair).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

proposed_standard_name‘ultraviolet_aerosol_index’ (static)

NC_STRING

comment‘Aerosol index from 380 and 340 nm’ (static)

NC_STRING

long_name‘Aerosol index from 380 and 340 nm’ (static)

NC_STRING

radiation_wavelength

340.0, 380.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index.
coordinates‘longitude latitude’ (static)

NC_STRING

ancillary_variables‘aerosol_index_340_380_precision’ (static)

NC_STRING

aerosol_index_335_367 in AER_AI/PRODUCTDescription:

The main output of the Aerosol Index retrieval algorithm (at wavelengths 354/388, i.e. theOMI pair).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

proposed_standard_name‘ultraviolet_aerosol_index’ (static)

NC_STRING

comment‘Aerosol index from 367 and 335 nm’ (static)

NC_STRING

long_name‘Aerosol index from 367 and 335 nm’ (static)

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335.0, 367.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index.
coordinates‘longitude latitude’ (static)

NC_STRING

ancillary_variables‘aerosol_index_335_367_precision’ (static)

NC_STRING

aerosol_index_354_388_precision in AER_AI/PRODUCTDescription:

The precision of the Aerosol Index retrieval algorithm (at wavelengths 354/388, i.e. the OMIpair).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

proposed_standard_name‘ultraviolet_aerosol_index standard_error’ (static)

NC_STRING

comment‘Precision of aerosol index from 388 and 354 nm’(static)

NC_STRING

long_name‘Precision of aerosol index from 388 and 354 nm’(static)

NC_STRING

radiation_wavelength354.0, 388.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index.
coordinates‘longitude latitude’ (static)

NC_STRING

aerosol_index_340_380_precision in AER_AI/PRODUCTDescription:

The precision of the Aerosol Index retrieval algorithm (at wavelengths 340/380, i.e. theTOMS pair).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

proposed_standard_name‘ultraviolet_aerosol_index standard_error’ (static)

NC_STRING

comment‘Precision of aerosol index from 380 and 340 nm’(static)

NC_STRING

long_name‘Precision of aerosol index from 380 and 340 nm’(static)

NC_STRING

radiation_wavelength

340.0, 380.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index.
coordinates‘longitude latitude’ (static)

NC_STRING

aerosol_index_335_367_precision in AER_AI/PRODUCTDescription:

The precision of the Aerosol Index retrieval algorithm (at wavelengths 354/388, i.e. the OMIpair).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

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units‘1’ (static)

NC_STRING

proposed_standard_name‘ultraviolet_aerosol_index standard_error’ (static)

NC_STRING

comment‘Precision of aerosol index from 367 and 335 nm’(static)

NC_STRING

long_name‘Precision of aerosol index from 367 and 335 nm’(static)

NC_STRING

radiation_wavelength

335.0, 367.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index.
coordinates

10.1.1‘longitude latitude’ (static)

NC_STRING

Group “SUPPORT_DATA” in “PRODUCT”

10.1.1.1

Group “GEOLOCATIONS” in “SUPPORT_DATA”

Variables in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
satellite_latitude in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
Description:

Latitude of the geodetic sub satellite point on the WGS84 reference ellipsoid.

Dimensions:time, scanline.

Type:

NC_FLOAT.

Source:

L1B.

Attributes:

Name

Value

Type

long_name‘sub satellite latitude’ (static)

NC_STRING

units‘degrees_north’ (static)

NC_STRING

comment‘Latitude of the geodetic sub satellite point on the
WGS84 reference ellipsoid’ (static)

NC_STRING

valid_min-90.0 (static)

NC_FLOAT

valid_max

90.0 (static)

NC_FLOAT

satellite_longitude in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
Description:

Longitude of the geodetic sub satellite point on the WGS84 reference ellipsoid.

Dimensions:time, scanline.

Type:

NC_FLOAT.

Source:

L1B.

Attributes:

Name

Value

Type

long_name‘satellite_longitude’ (static)

NC_STRING

units‘degrees_east’ (static)

NC_STRING

comment‘Longitude of the geodetic sub satellite point on the
WGS84 reference ellipsoid’ (static)

NC_STRING

valid_min-180.0 (static)

NC_FLOAT

valid_max

180.0 (static)

NC_FLOAT

satellite_altitude in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
Description:

The altitude of the satellite with respect to the geodetic sub satellite point on the WGS84
reference ellipsoid.

Dimensions:time, scanline.

Type:

NC_FLOAT.

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Source:

L1B.

Attributes:

Name

Value

Type

long_name‘satellite altitude’ (static)

NC_STRINGunits‘m’ (static)

NC_STRING

comment‘The altitude of the satellite with respect to the geodetic sub satellite point on the WGS84 reference
ellipsoid’ (static)

NC_STRING

valid_min

700000.0 (static)

NC_FLOAT

valid_max

900000.0 (static)

NC_FLOAT

satellite_orbit_phase in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
Description:

Relative offset [0.0, . . . , 1.0] of the measurement in the orbit.

Dimensions:time, scanline.

Type:

NC_FLOAT.

Source:

L1B.

Attributes:

Name

Value

Type

long_name‘fractional satellite orbit phase’ (static)

NC_STRINGunits‘1’ (static)

NC_STRING

comment‘Relative offset [0.0, ..., 1.0] of the measurement in
the orbit’ (static)

NC_STRING

valid_min-0.02 (static)

NC_FLOAT

valid_max

1.02 (static)

NC_FLOAT

solar_zenith_angle in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
Description:

Solar zenith angle ϑ0 at the ground pixel location on the reference ellipsoid. Angle ismeasured away from the vertical. ESA definition of day side: ϑ0 < 92◦ . Pixels are processed
when ϑ0 ≤ ϑ0max with 80◦ ≤ ϑ0max ≤ 88◦ , depending on the algorithm. The actual value forϑ0max can be found in the algorithm metadata settings.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:

L1B.

Attributes:

Name

Value

Type

long_name‘solar zenith angle’ (static)

NC_STRING

standard_name‘solar_zenith_angle’ (static)

NC_STRING

units‘degree’ (static)

NC_STRING

valid_min

0.0 (static)

NC_FLOAT

valid_max

180.0 (static)

NC_FLOAT

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
comment‘Solar zenith angle at the ground pixel location on
the reference ellipsoid. Angle is measured awayfrom the vertical’ (static)

NC_STRING

solar_azimuth_angle in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
Description:

The solar azimuth angle at the ground pixel location on the reference ellipsoid. The angle ismeasured clockwise from the North (North = 0◦ , East = 90◦ , South = ±180◦ , West = −90◦ ).
This is the same definition that is use in both OMI and GOME-2 level 1B files.
See the note on the viewing_azimuth_angle on the calculation of the relative azimuth
angle as used in radiative transfer calculations.

Dimensions:time, scanline, ground_pixel.

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Type:

NC_FLOAT.

Source:

L1B.

Attributes:

Name

Value

Type

long_name‘solar azimuth angle’ (static)

NC_STRING

standard_name‘solar_azimuth_angle’ (static)

NC_STRING

units‘degree’ (static)

NC_STRING

valid_min-180.0 (static)

NC_FLOAT

valid_max

180.0 (static)

NC_FLOAT

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
comment‘Solar azimuth angle at the ground pixel location on
the reference ellipsoid. Angle is measured clockwise from the North (East = 90, South = +/-180,
West = -90)’ (static)

NC_STRING

viewing_zenith_angle in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
Description:

Zenith angle of the satellite ϑ at the ground pixel location on the reference ellipsoid. Angle
is measured away from the vertical.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:

L1B.

Attributes:

Name

Value

Type

long_name‘viewing zenith angle’ (static)

NC_STRING

standard_name‘viewing_zenith_angle’ (static)

NC_STRING

units‘degree’ (static)

NC_STRING

valid_min

0.0 (static)

NC_FLOAT

valid_max

180.0 (static)

NC_FLOAT

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
comment‘Zenith angle of the satellite at the ground pixel location on the reference ellipsoid. Angle is measured
away from the vertical’ (static)

NC_STRING

viewing_azimuth_angle in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
Description:

The satellite azimuth angle at the ground pixel location on the reference ellipsoid. The angle
is measured clockwise from the North (North = 0◦ , East = 90◦ , South = ±180◦ , West =−90◦ ). This is the same definition that is use in both OMI and GOME-2 level 1B files.
To calculate the azimuth difference ϕ − ϕ0 it is not sufficient to just subtract solar_azimuth_angle from viewing_azimuth_angle. The angle needed for radiative transfer calculations is (180◦ − (ϕ − ϕ0 )) mod 360◦ .

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:

L1B.

Attributes:

Name

Value

Type

long_name‘viewing azimuth angle’ (static)

NC_STRING

standard_name‘viewing_azimuth_angle’ (static)

NC_STRING

units‘degree’ (static)

NC_STRING

valid_min-180.0 (static)

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valid_max

180.0 (static)

NC_FLOAT

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
comment‘Satellite azimuth angle at the ground pixel location on the reference ellipsoid. Angle is measured
clockwise from the North (East = 90, South = +/-180, West = -90)’ (static)

NC_STRING

latitude_bounds in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
Description:

The latitude of the pixel corners of the ground pixels in the data. Latitude, longitude
coordinates for the ground pixel center and the ground pixel corners are calculated at the
WGS84 ellipsoid.
The order of the pixel corners follows the CF-metadata conventions [ER5, section 7.1], i.e.
the ordering is counter-clockwise when viewed from above. A graphical representation is
given in figure 8.

Dimensions:time, scanline, ground_pixel, corner.

Type:

NC_FLOAT.

Source:Processor.

longitude_bounds in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
Description:

The longitude of the pixel corners of the ground pixels in the data. Latitude, longitude
coordinates for the ground pixel center and the ground pixel corners are calculated at the
WGS84 ellipsoid.
The order of the pixel corners follows the CF-metadata conventions [ER5, section 7.1], i.e.
the ordering is counter-clockwise when viewed from above. A graphical representation is
given in figure 8.

Dimensions:time, scanline, ground_pixel, corner.

Type:

NC_FLOAT.

Source:Processor.

geolocation_flags in AER_AI/PRODUCT/SUPPORT_DATA/GEOLOCATIONS
Description:

Additional flags describing the ground pixel, including the influence of a solar eclipse, thepossibility of sun glint, whether we are in the descending part of the orbit, whether we areon the night side of the orbit, whether the pixel crosses the dateline (useful for plotting), or if
there was some geolocation error.

Dimensions:time, scanline, ground_pixel.

Type:

NC_UBYTE.

Source:Processor.

Attributes:

Name

Value

Type

_FillValue

255 (static)

NC_UBYTE

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

flag_masks

0, 1, 2, 4, 8, 16, 32, 128 (static)

NC_UBYTE

flag_meanings‘no_error solar_eclipse sun_glint_possible descending night geo_boundary_crossing spacecraft_manoeuvre geolocation_error’ (static)

NC_STRING

flag_values

0, 1, 2, 4, 8, 16, 32, 128 (static)

NC_UBYTE

long_name‘geolocation flags’ (static)

NC_STRING

max_val254 (static)

NC_UBYTE

min_val

0 (static)

NC_UBYTE

units‘1’ (static)

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Group “DETAILED_RESULTS” in “SUPPORT_DATA”

Variables in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
processing_quality_flags in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

Processing quality flag. This flag indicates processing errors or reasons for not processinga particular pixel (collectively ‘errors’, leading to a fill value in the output) and warnings that
occured while processing this pixel (warnings which may affect the quality of the retrieval
result). A detailed description is provided in appendix A.

Dimensions:time, scanline, ground_pixel.

Type:

NC_UINT.

Source:Processor.

Attributes:

Name

Value

long_name‘Processing quality flags’ (static)

NC_STRING

comment‘Flags indicating conditions that affect quality of theretrieval.’ (static)

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input_spectrum_missing reflectance_range_error
ler_range_error snr_range_error sza_range_error
vza_range_error lut_range_error ozone_range_error wavelength_offset_error initialization_error
memory_error assertion_error io_error numerical_error lut_error ISRF_error convergence_error
cloud_filter_convergence_error max_iteration_convergence_error aot_lower_boundary_convergence_error other_boundary_convergence_error
geolocation_error ch4_noscat_zero_error h2o_noscat_zero_error max_optical_thickness_error
aerosol_boundary_error
boundary_hit_error
chi2_error svd_error dfs_error radiative_transfer_error optimal_estimation_error profile_error
cloud_error
model_error
number_of_input_data_points_too_low_error
cloud_pressure_spread_too_low_error cloud_too_low_level_error
generic_range_error generic_exception input_spectrum_alignment_error abort_error wrong_input_type_error
wavelength_calibration_error
coregistration_error slant_column_density_error
airmass_factor_error vertical_column_density_error signal_to_noise_ratio_error configuration_error
key_error saturation_error max_num_outlier_exceeded_error solar_eclipse_filter cloud_filter
altitude_consistency_filter altitude_roughness_filter sun_glint_filter mixed_surface_type_filter
snow_ice_filter aai_filter cloud_fraction_fresco_filter aai_scene_albedo_filter small_pixel_radiance_std_filter cloud_fraction_viirs_filter cirrus_reflectance_viirs_filter
cf_viirs_swir_ifov_filter
cf_viirs_swir_ofova_filter cf_viirs_swir_ofovb_filter
cf_viirs_swir_ofovc_filter
cf_viirs_nir_ifov_filter
cf_viirs_nir_ofova_filter cf_viirs_nir_ofovb_filter
cf_viirs_nir_ofovc_filter refl_cirrus_viirs_swir_filter
refl_cirrus_viirs_nir_filter diff_refl_cirrus_viirs_filter
ch4_noscat_ratio_filter ch4_noscat_ratio_std_filter
h2o_noscat_ratio_filter h2o_noscat_ratio_std_filter
diff_psurf_fresco_ecmwf_filter
psurf_fresco_stdv_filter ocean_filter time_range_filter pixel_or_scanline_index_filter geographic_region_filter
input_spectrum_warning wavelength_calibration_warning extrapolation_warning sun_glint_warningsouth_atlantic_anomaly_warning
sun_glint_correction snow_ice_warning cloud_warning
AAI_warning
pixel_level_input_data_missing
data_range_warning low_cloud_fraction_warning altitude_consistency_warning signal_to_noise_ratio_warning
deconvolution_warning
so2_volcanic_origin_likely_warning so2_volcanic_origin_certain_warninginterpolation_warning
saturation_warning high_sza_warning cloud_retrieval_warning cloud_inhomogeneity_warningthermal_instability_warning’ (static)

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flag_masks

255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 256, 512, 1024, 2048, 4096, 8192,
16384, 32768, 65536, 131072, 262144, 524288,
1048576, 2097152, 4194304, 8388608, 16777216,
33554432, 67108864, 134217728, 268435456,
536870912, 1073741824 (static)

NC_UINT

flag_values

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,
44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 64, 65,
66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,
80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93,
94, 95, 96, 97, 256, 512, 1024, 2048, 4096, 8192,
16384, 32768, 65536, 131072, 262144, 524288,
1048576, 2097152, 4194304, 8388608, 16777216,
33554432, 67108864, 134217728, 268435456,
536870912, 1073741824 (static)

NC_UINT

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
number_of_spectral_points_in_retrieval in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The number of points in the spectrum that were used in the retrieval.

Dimensions:time, scanline, ground_pixel.

Type:

NC_USHORT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘Number of spectral points used in the retrieval’(static)

NC_STRING

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
scene_albedo_388 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

Scene albedo at 388 nm (calculated from top of atmosphere reflectance).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

long_name‘Scene albedo at 388 nm calculated from the top of
atmosphere reflectance. For a cloud- and aerosolfree scene this is equivalent to the surface albedo’(static)

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388.0 (static)

NC_FLOAT

The wavelengthat which the surface albedo was determined. The CF-conventions propose
to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘scene_albedo_388_precision’ (static)

NC_STRING

scene_albedo_388_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

Precision of the scene albedo at 388 nm (calculated from top of atmosphere reflectanceand the precision of the reflectance).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

units

‘1’ (static)

NC_STRING

long_name‘Precision of the scene albedo at 388 nm calculated from the top of atmosphere reflectance andits precision. For a cloud- and aerosol-free scene
this is equivalent to the surface albedo’ (static)

NC_STRING

radiation_wavelength

388.0 (static)

NC_FLOATType

The wavelengthat which the surface albedo was determined. The CF-conventions propose
to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
reflectance_measured_354 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The top of atmosphere reflectance at 354 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance’ (static)

NC_STRING

long_name‘Top of atmosphere reflectance at 354 nm’ (static)

NC_STRING

radiation_wavelength354.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘reflectance_measured_354_precision’ (static)

NC_STRING

reflectance_measured_354_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS

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The precision of the top of atmosphere reflectance at 354 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance(static)

standard_error’

NC_STRING

long_name‘Precision of the top of atmosphere reflectance at
354 nm’ (static)

NC_STRING

radiation_wavelength354.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
reflectance_measured_388 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The top of atmosphere reflectance at 388 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance’ (static)

NC_STRING

long_name‘Top of atmosphere reflectance at 388 nm’ (static)

NC_STRING

radiation_wavelength

388.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘reflectance_measured_388_precision’ (static)

NC_STRING

reflectance_measured_388_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The precision of the top of atmosphere reflectance at 388 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance(static)

standard_error’

NC_STRING

long_name‘Precision of the top of atmosphere reflectance at
388 nm’ (static)

NC_STRING

radiation_wavelength

388.0 (static)

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The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
reflectance_calculated_354 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The calculated top of atmosphere reflectance at 354 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance’ (static)

NC_STRING

long_name‘Calculated top of atmosphere reflectance at 354
nm’ (static)

NC_STRING

radiation_wavelength354.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘reflectance_calculated_354_precision’ (static)

NC_STRING

reflectance_calculated_354_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The precision of the calculated top of atmosphere reflectance at 354 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

units

‘1’ (static)

standard_name‘toa_bidirectional_reflectance(static)

standard_error’

NC_STRING

long_name‘Precision of the calculated top of atmosphere reflectance at 354 nm’ (static)

NC_STRING

radiation_wavelength354.0 (static)

NC_FLOATType
NC_STRING

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
scene_albedo_380 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

Scene albedo at 380 nm (calculated from top of atmosphere refelctance).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

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Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

long_name‘Scene albedo at 380 nm calculated from the top of
atmosphere reflectance. For a cloud- and aerosolfree scene this is equivalent to the surface albedo’(static)

NC_STRING

radiation_wavelength

380.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘scene_albedo_380_precision’ (static)

NC_STRING

scene_albedo_380_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

Precision of the scene albedo at 380 nm (calculated from top of atmosphere reflectanceand the precision of the reflectance).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

long_name‘Precision of the scene albedo at 380 nm calculated from the top of atmosphere reflectance andits precision. For a cloud- and aerosol-free scene
this is equivalent to the surface albedo’ (static)

NC_STRING

radiation_wavelength

380.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
reflectance_measured_340 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The top of atmosphere reflectance at 340 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance’ (static)

NC_STRING

long_name‘Top of atmosphere reflectance at 340 nm’ (static)

NC_STRING

radiation_wavelength

340.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.

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coordinates

S5P-KNMI-L2-0026-MA
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NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘reflectance_measured_340_precision’ (static)

NC_STRING

reflectance_measured_340_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The precision of the top of atmosphere reflectance at 340 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance(static)

standard_error’

NC_STRING

long_name‘Precision of the top of atmosphere reflectance at
340 nm’ (static)

NC_STRING

radiation_wavelength

340.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
reflectance_measured_380 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The top of atmosphere reflectance at 380 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance’ (static)

NC_STRING

long_name‘Top of atmosphere reflectance at 380 nm’ (static)

NC_STRING

radiation_wavelength

380.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘reflectance_measured_380_precision’ (static)

NC_STRING

reflectance_measured_380_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The precision of the top of atmosphere reflectance at 380 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

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units‘1’ (static)

standard_name‘toa_bidirectional_reflectance(static)

standard_error’

NC_STRING

long_name‘Precision of the top of atmosphere reflectance at
380 nm’ (static)

NC_STRING

radiation_wavelength

380.0 (static)

NC_FLOAT

NC_STRING

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
reflectance_calculated_340 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The calculated top of atmosphere reflectance at 340 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance’ (static)

NC_STRING

long_name‘Calculated top of atmosphere reflectance at 340
nm’ (static)

NC_STRING

radiation_wavelength

340.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘reflectance_calculated_340_precision’ (static)

NC_STRING

reflectance_calculated_340_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

Precision of the calculated top of atmosphere reflectance at 340 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance(static)

standard_error’

NC_STRING

long_name‘Precision of the calculated top of atmosphere reflectance at 340 nm’ (static)

NC_STRING

radiation_wavelength

340.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

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The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
scene_albedo_367 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

Scene albedo at 367 nm (calculated from top of atmosphere reflectance).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

long_name‘Scene albedo at 367 nm calculated from the top of
atmosphere reflectance. For a cloud- and aerosolfree scene this is equivalent to the surface albedo’(static)

NC_STRING

radiation_wavelength

367.0 (static)

NC_FLOAT

The wavelengthat which the surface albedo was determined. The CF-conventions propose
to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘scene_albedo_367_precision’ (static)

NC_STRING

scene_albedo_367_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

Precision of the scene albedo at 367 nm (calculated from top of atmosphere reflectanceand the precision of the reflectance).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

long_name‘Precision of the scene albedo at 367 nm calculated from the top of atmosphere reflectance andits precision. For a cloud- and aerosol-free scene
this is equivalent to the surface albedo’ (static)

NC_STRING

radiation_wavelength

367.0 (static)

NC_FLOAT

The wavelengthat which the surface albedo was determined. The CF-conventions propose
to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
reflectance_measured_335 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The top of atmosphere reflectance at 335 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

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units‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance’ (static)

NC_STRING

long_name‘Top of atmosphere reflectance at 335 nm’ (static)

NC_STRING

radiation_wavelength

335.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘reflectance_measured_335_precision’ (static)

NC_STRING

reflectance_measured_335_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The precision of the top of atmosphere reflectance at 335 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance(static)

standard_error’

NC_STRING

long_name‘Precision of the top of atmosphere reflectance at
335 nm’ (static)

NC_STRING

radiation_wavelength

335.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
reflectance_measured_367 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The top of atmosphere reflectance at 367 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance’ (static)

NC_STRING

long_name‘Top of atmosphere reflectance at 367 nm’ (static)

NC_STRING

radiation_wavelength

367.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].

S5P L2 PUM UV Aerosol Index
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ancillary_variables

S5P-KNMI-L2-0026-MA
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NC_STRING

reflectance_measured_367_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The precision of the top of atmosphere reflectance at 367 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance(static)

standard_error’

NC_STRING

long_name‘Precision of the top of atmosphere reflectance at
367 nm’ (static)

NC_STRING

radiation_wavelength

367.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
reflectance_calculated_335 in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The calculated top of atmosphere reflectance at 335 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance’ (static)

NC_STRING

long_name‘Calculated top of atmosphere reflectance at 335
nm’ (static)

NC_STRING

radiation_wavelength

335.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘reflectance_calculated_335_precision’ (static)

NC_STRING

reflectance_calculated_335_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The precision of the calculated top of atmosphere reflectance at 335 nm.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (static)

NC_STRING

standard_name‘toa_bidirectional_reflectance(static)

standard_error’

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long_name‘Precision of the calculated top of atmosphere reflectance at 335 nm’ (static)

NC_STRING

radiation_wavelength

335.0 (static)

NC_FLOAT

The wavelengths used for the determination of the aerosol index. The CF-conventions
propose to use a coordinate variable for this, but this seems more appropriate.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
wavelength_calibration_offset in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

Fitted wavelength offset from the wavelength calibration pre-fit in the Level 2 processor.

λtrue = λnominal + δ λ(1)See [RD35] for details about the wavelength fit.
Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘wavelength offset’ (static)

NC_STRING

units‘nm’ (static)

NC_STRING

wavelength_fit_window_start

0.0 (static)

NC_FLOAT

The start wavelength of the wavelength fit window.
wavelength_fit_window_end

0.0 (static)

NC_FLOATThe end wavelength of the wavelength fit window.
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘wavelength_calibration_offset_precision’ (static)

NC_STRING

comment‘True wavelength = nominal wavelength +wavelength offset + wavelength stretch * scaled
wavelength’ (static)

NC_STRING

wavelength_calibration_offset_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

A posteriori precision of the fitted wavelength offset.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘wavelength offset precision’ (static)

NC_STRING

units‘nm’ (static)

NC_STRING

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
wavelength_calibration_stretch in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS

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Description:

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Fitted wavelength stretch q from the wavelength calibration pre-fit in the Level 2 processor.

λtrue = λnominal + δ λ + qλ ∗(2)with λ ∗ a scaled wavelength to the range [−1, 1] over the full fit window. This is an optional
fit parameter.
Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘wavelength stretch’ (static)

NC_STRINGunits‘1’ (static)

NC_STRING

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
ancillary_variables‘wavelength_calibration_stretch_precision’ (static)

NC_STRING

comment‘True wavelength = nominal wavelength +wavelength offset + wavelength stretch * scaled
wavelength’ (static)

NC_STRING

wavelength_calibration_stretch_precision in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

A posteriori precision of the fitted wavelength stretch.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘wavelength stretch precision’ (static)

NC_STRINGunits‘1’ (static)

NC_STRING

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
wavelength_calibration_chi_square in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The χ 2 from the wavelength calibration pre-fit in the Level 2 processor.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘wavelength calibration chi square’ (static)

NC_STRINGunits‘1’ (static)

NC_STRING

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
wavelength_calibration_irradiance_offset in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS

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Description:

Fitted wavelength offset from the irradiance wavelength calibration pre-fit in hte Level 2
processor.
λtrue = λnominal + δ λ(3)Dimensions:time, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

long_name‘irradiance wavelength offset’ (static)

NC_STRING

units‘nm’ (static)

NC_STRING

wavelength_fit_window_start

0.0 (static)

NC_FLOAT

See [RD35] for details about the wavelength fit.

Type

The start wavelength of the irradiance wavelength fit window.
wavelength_fit_window_end

0.0 (static)

NC_FLOATThe end wavelength of the irradiance wavelength fit window.
ancillary_variables‘wavelength_calibration_irradiance_offset_precision’ (static)

NC_STRING

comment‘True wavelength = nominal wavelength +wavelength offset + wavelength stretch * scaled
wavelength’ (static)

NC_STRING

wavelength_calibration_irradiance_offset_precision
DETAILED_RESULTS

in

AER_AI/PRODUCT/SUPPORT_DATA/

Description:

A posteriori precision of the fitted wavelength offset for the irradiance spectrum.

Dimensions:time, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘irradiance wavelength offset precision’ (static)

NC_STRING

units‘nm’ (static)

NC_STRING

wavelength_calibration_irradiance_chi_square in AER_AI/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS
Description:

The χ 2 from the irradiance wavelength calibration pre-fit in the Level 2 processor.

Dimensions:time, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘wavelength calibration irradiance chi squared’(static)

NC_STRINGunits‘1’ (static)

NC_STRING

10.1.1.3

Group “INPUT_DATA” in “SUPPORT_DATA”

Variables in AER_AI/PRODUCT/SUPPORT_DATA/INPUT_DATA
surface_altitude in AER_AI/PRODUCT/SUPPORT_DATA/INPUT_DATA
Description:

The mean of the sub-pixels of the surface altitude within the approximate field of view, basedon the GMTED2010 surface elevation database. The surface altitude is referenced to the
Earth Gravitational Model 1996 (EGM96) geoid.

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Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:surface elevation database.

Attributes:

Name

Value

Type

long_name‘Surface altitude’ (static)

NC_STRING

standard_name‘surface_altitude’ (static)

NC_STRINGunits‘m’ (static)

NC_STRING

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

source‘http://topotools.cr.usgs.gov/gmted_viewer/’ (static)

NC_STRING

comment‘The mean of the sub-pixels of the surface altitudewithin the approximate field of view, based on the
GMTED2010 surface elevation database’ (static)

NC_STRING

surface_altitude_precision in AER_AI/PRODUCT/SUPPORT_DATA/INPUT_DATA
Description:

The standard deviation of sub-pixels used in calculating the mean surface altitude, basedon the GMTED2010 surface elevation database. See the description of the surface_altitude variable for details.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:surface elevation database.

Attributes:

Name

Value

Type

long_name‘surface altitude precision’ (static)

NC_STRING

standard_name‘surface_altitude standard_error’ (static)

NC_STRINGunits‘m’ (static)

NC_STRING

standard_error_multiplier

1.0 (static)

NC_FLOAT

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

source‘http://topotools.cr.usgs.gov/gmted_viewer/’ (static)

NC_STRING

comment‘The standard deviation of sub-pixels used in calculating the mean surface altitude, based on the
GMTED2010 surface elevation database’ (static)

NC_STRING

surface_classification in AER_AI/PRODUCT/SUPPORT_DATA/INPUT_DATA
Description:

This is a combined land/water mask and surface classification data field. For land the“Global Land Cover Characteristics Data Base Version 2.0” is used [ER8], specifically the“USGS Land Use/Land Cover System (Modified Level 2)” classification. Over water theclassification from the NASA SDP toolkit [ER9], which is based on [RD36].
The structure of this variable is indicated with the flag_meanings, flag_values and flag_masks, following the CF-metadata convensions. Bits 0 and 1 indicate the land-water mask
at two levels, bit 2 gives a rough statistic on the coverage of the pixel, and the remainder ofthe byte indicates the surface classification in more detail. Note that these values are staticand based on the databases indicated above.

Dimensions:time, scanline, ground_pixel.

Type:

NC_UBYTE.

Source:surface elevation database (including flag attributes).

Attributes:

Name

Value

Type

long_name‘Land-water mask and surface classification basedon a static database’ (static)

NC_STRING

comment‘Flag indicating land/water and further surface classifications for the ground pixel’ (static)

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source‘USGS (https://lta.cr.usgs.gov/GLCC) and NASASDP toolkit (http://newsroom.gsfc.nasa.gov/
sdptoolkit/toolkit.html)’ (static)

NC_STRING

flag_meanings‘land water some_water coast value_covers_majority_of_pixel
water+shallow_ocean
water+shallow_inland_water
water+ocean_coastline-lake_shoreline water+intermittent_water
water+deep_inland_water
water+continental_shelf_ocean water+deep_ocean land+urban_and_built-up_land
land+dryland_cropland_and_pasture land+irrigated_cropland_and_pastureland+mixed_dryland-irrigated_cropland_and_pasture land+cropland-grassland_mosaic
land+cropland-woodland_mosaic land+grassland
land+shrublandland+mixed_shrublandgrassland
land+savanna
land+deciduous_broadleaf_forest
land+deciduous_needleleaf_forest
land+evergreen_broadleaf_forest
land+evergreen_needleleaf_forest land+mixed_forest land+herbaceous_wetland land+wooded_wetland
land+barren_or_sparsely_vegetatedland+herbaceous_tundra land+wooded_tundra
land+mixed_tundra
land+bare_ground_tundra
land+snow_or_ice’ (static)

NC_STRING

flag_values

0, 1, 2, 3, 4, 9, 17, 25, 33, 41, 49, 57, 8, 16, 24, 32,
40, 48, 56, 64, 72, 80, 88, 96, 104, 112, 120, 128,
136, 144, 152, 160, 168, 176, 184 (static)

NC_UBYTE

flag_masks

3, 3, 3, 3, 4, 249, 249, 249, 249, 249, 249, 249,
249, 249, 249, 249, 249, 249, 249, 249, 249, 249,
249, 249, 249, 249, 249, 249, 249, 249, 249, 249,
249, 249, 249 (static)

NC_UBYTE

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

instrument_configuration_identifier in AER_AI/PRODUCT/SUPPORT_DATA/INPUT_DATA
Description:

The IcID from the instrument configuration in the Level 1B data product. The TROPOMI
instrument has many configurable parameters. For example, the exposure time, co-addition
period, gains and (for UVN-DEMs) the binning factors can be varied. As a result, theinstrument can be operated in many different modes or configurations. Each combinationof instrument settings is referred to as an instrument configuration and is identified by an
instrument configuration ID, a number in the range [1, 65535]. This instrument configuration
ID, or IcID, is primarily used by the instrument, where it identifies an entry in the instrument
configuration tables. On ground, the IcID is used to determine the intended purpose of ameasurement and is used in the L0 to 1b data processing to determine the processing path.

Dimensions:time, scanline.

Type:

NC_INT.

Source:

L1B.

Attributes:

Name

Value

Type

long_name‘IcID’ (static)

NC_STRING

comment‘The Instrument Configuration ID defines the typeof measurement and its purpose. The number of
instrument configuration IDs will increase over the
mission as new types of measurements are createdand used’ (static)

NC_STRING

instrument_configuration_version in AER_AI/PRODUCT/SUPPORT_DATA/INPUT_DATAS5P L2 PUM UV Aerosol Index
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For an IcID (see the instrument_configuration_identifier above), it is possible
to have multiple versions, identified by the instrument configuration version or IcVersion.
The combination of IcID and IcVersion uniquely identifies the set of configuration settingsof the instrument. At a given time, only one IcVersion of an IcID can be active within the
instrument. The IcVersion allows to have multiple versions of a measurement with the same
purpose, but with different settings. As a result of, for example, instrument degradation, it
may be required to change the settings for a measurement. In that case, it is not necessary
to create a new IcID, instead the same IcID can be using with a new IcVersion.

Dimensions:time, scanline.

Type:

NC_SHORT.

Source:

L1B.

Attributes:

Name

Value

Type

long_name‘IcVersion’ (static)

NC_STRING

comment‘Version of the instrument_configuration_identifier’(static)

NC_STRING

scaled_small_pixel_variance in AER_AI/PRODUCT/SUPPORT_DATA/INPUT_DATA
Description:

The scaled variance of the small pixel values for each ground pixel.

hR(t, r, c)i =V (t, r, c) =Vscaled (t, r, c) =1
Nsmall pixels
1
Nsmall pixels

Nsmall pixels −1∑

R(t, r, c, i)(4)(R(t, r, c, i) − hR(t, r, c)i)2

(5)

i=0
Nsmall pixels −1∑

i=0

V (t, r, c)(6)hR(t, r, c)i2

with hR(t, r, c)i the mean reflectance for small pixels of ground pixel (t, r, c), V (t, r, c) the
variance of the small pixels, Vscaled (t, r, c) the scaled small pixel variance, and R(t, r, c, i) withi = [0, . . . , Nsmall pixels − 1] the small pixel reflectance of ground pixel (t, r, c). The reflectance
R is calculated as R = (πI)/(µ0 E0 ), with I the radiance, E0 the irradiance and µ0 = cos(ϑ0 ),where ϑ0 is the solar zenith angle.
Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

long_name‘scaled small pixel variance’ (static)

NC_STRINGunits‘1’ (static)

NC_STRING

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
comment‘The scaled variance of the reflectances of thesmall pixels’ (static)

radiation_wavelength

NC_STRING
NC_FLOATThe approximate wavelength of the small pixel column in nm. Note that due to the spectral
smile this wavelength will depend on the ground_pixel index.
eastward_wind in AER_AI/PRODUCT/SUPPORT_DATA/INPUT_DATA
Description:

The horizontal component of the wind at 10 meter height in the eastward direction. This is
the 10U parameter from ECMWF (grib variable 165).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

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Source:Processor.

Attributes:

Name

Value

Type

standard_name‘eastward_wind’ (static)

NC_STRING

long_name‘Eastward wind from ECMWF at 10 meter heightlevel’ (static)

NC_STRINGunits‘m s-1’ (static)

NC_STRING

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

ancillary_variables‘northward_wind’ (static)

NC_STRING

northward_wind in AER_AI/PRODUCT/SUPPORT_DATA/INPUT_DATA
Description:

The horizontal component of the wind at 10 meter height in the northward direction. This is
the 10V parameter from ECMWF (grib variable 166).

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

standard_name‘northward_wind’ (static)

NC_STRING

long_name‘Northward wind from ECMWF at 10 meter heightlevel’ (static)

NC_STRINGunits‘m s-1’ (static)

NC_STRING

coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

ancillary_variables‘eastward_wind’ (static)

NC_STRING

ozone_total_column in AER_AI/PRODUCT/SUPPORT_DATA/INPUT_DATA
Description:

Total O3 column from ECMWF model data.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘mol m-2’ (static)

NC_STRING

standard_name‘atmosphere_mole_content_of_ozone’ (static)

NC_STRING

long_name‘total column amount of ozone from ECMWF model
data’ (static)

NC_STRING

source

NC_STRING

Possible values: ECMWF, Multi-sensor reanalysis (climatology)
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].
multiplication_factor_to_convert_to_DU

2241.15 (static)

NC_FLOATThe quantities in Sentinel 5 precursor files are given in SI units. For an integrated column
value this means that the unit is mol m−2 . Traditionally the unit for an integrated column is“DU” or Dobson Units. This attribute provides the multiplication factor to calculate the total
column in DU from the value in mol m−2 . This is provided as a convenience to users who
have tools that work in DU.

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multiplication_factor_to_convert_to_molecules_percm2

6.022140857e+19 (static)

NC_FLOATThe quantities in Sentinel 5 precursor files are given in SI units. For an integrated column
value this means that the unit is mol m−2 . Traditionally the unit for an integrated column
is “molecules cm−2 ”. This attribute provides the multiplication factor to calculate the total
column in molecules cm−2 from the value in mol m−2 . This is provided as a convenience tousers who have tools that work in molecules cm−2 .
surface_pressure in AER_AI/PRODUCT/SUPPORT_DATA/INPUT_DATA
Description:

Surface pressure, corrected for the difference between the surface altitude in the DEM andthe surface altitude assumed by ECMWF.

Dimensions:time, scanline, ground_pixel.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘Pa’ (static)

NC_STRING

standard_name‘surface_air_pressure’ (static)

NC_STRING

long_name‘surface_air_pressure’ (static)

NC_STRING

source

NC_STRING

Possible values: ECMWF, Using DEM and assuming fixed sea-level pressure of 1013 hPa
and scale height of 8.3 km
coordinates‘/PRODUCT/longitude /PRODUCT/latitude’ (static)

NC_STRING

The latitude and longitude are in a different group. How to specify the related geospatial
coordinates in this case is not specified in the climate and forecast metadata conventions [ER5].

10.2

Group “METADATA” in “AER_AI”

This is a group to collect metadata items, such as the items that also appear in the header file and items
required by Inspire [ER4]. Most metadata will be stored as attributes. Grouping attributes that belong to a
specific standard is done by using sub-groups in the Metadata group. Included in this group are the granuledescription, algorithm settings and quality assurance parameters. Note that some metadata attributes are
required to be attached to the global level by convention, such as the CF-Metadata convention [ER5] and the
NetCDF user guide [ER7].
10.2.1

Group “QA_STATISTICS” in “METADATA”

Quality assurance statistics are gathered in variables located in this group. These can include histograms ofthe main parameters and event occurrence statistics. The contents of this group is under discussion. Note that
the QA statistics may be stored as scalar variables rather than attributes. The former allow attributes to be
attached to them, providing a more meaningful description than just the name.
Attributes in AER_AI/METADATA/QA_STATISTICS
Group attributes attached to QA_STATISTICS
Name

Value

Type

number_of_groundpixels

0 (static)

NC_INT

Number of ground pixels in the file.
number_of_processed_pixels

0 (static)

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Number of ground pixels where a retrieval was attempted. This is the number_of_groundpixels minus
the pixels that were rejected based on time or configuration (range and step-size in scanline or ground_pixel
index).
number_of_successfully_processed_pixels

0 (static)

NC_INT

Number of ground pixels where a retrieval was successful.
number_of_rejected_pixels_not_enough_spectrum

0 (static)

NC_INT

Number of pixels where processing was not attempted because after filtering for bad and missing pixels there
were not enough spectral pixels left in either the radiance, irradiance or after calculating the reflectance.
number_of_failed_retrievals

0 (static)

NC_INT

Number of pixels where processing failed for whatever reason.
number_of_ground_pixels_with_warnings

0 (static)

NC_INT

Number of pixels with one or more warnings.
number_of_missing_scanlines

0 (static)

NC_INT

Number of scanlines that are missing from the input.
number_of_radiance_missing_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “the number of spectral pixels in the radiance due toflagging is too small to perform the fitting” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “1”.
number_of_irradiance_missing_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “the number of spectral pixels in the irradiance due toflagging is too small to perform the fitting” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “2”.
number_of_input_spectrum_missing_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “the reflectance spectrum does not contain enough points
to perform the retrieval. This is different from (ir)radiance_missing in that the missing points may not bealigned” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “3”.
number_of_reflectance_range_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “any of the reflectances is out of bounds (R < 0 or
R > Rmax )” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “4”.
number_of_ler_range_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “lambert-equivalent reflectivity out of range error” occurred,
i.e. where the lower 8 bits of the processing_quality_flags have the value “5”.
number_of_snr_range_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “too low signal to noise to perform retrieval” occurred, i.e.
where the lower 8 bits of the processing_quality_flags have the value “6”.
number_of_sza_range_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “solar zenith angle out of range, maximum value from
configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value“7”.
number_of_vza_range_error_occurrences

0 (static)

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Number of ground pixels where processing error “viewing zenith angle out of range, maximum value from
configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value“8”.
number_of_lut_range_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “extrapolation in lookup table (airmass factor, cloudradiances)” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “9”.
number_of_ozone_range_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “ozone column significantly out of range of profile climatology” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value“10”.
number_of_wavelength_offset_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “wavelength offset exceeds maximum from configuration”
occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “11”.
number_of_initialization_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “an error occurred during the processing of the pixel, no
output was generated. The following errors raise this flag: Mismatch between irradiance and radiancewavelengths; The on-ground distance between band 1 and band 2 ground pixels exceeds a threshold set in
the configuration. Derived a-priori information does not validate, no processing is possible” occurred, i.e.
where the lower 8 bits of the processing_quality_flags have the value “12”.
number_of_memory_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “memory allocation or deallocation error” occurred, i.e.
where the lower 8 bits of the processing_quality_flags have the value “13”.
number_of_assertion_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “error in algorithm detected during assertion” occurred, i.e.
where the lower 8 bits of the processing_quality_flags have the value “14”.
number_of_io_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “error detected during transfer of data between algorithm
and framework” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value“15”.
number_of_numerical_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “general fatal numerical error occurred during inversion”
occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “16”.
number_of_lut_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “error in accessing the lookup table” occurred, i.e. where
the lower 8 bits of the processing_quality_flags have the value “17”.
number_of_ISRF_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “error detected in the input instrument spectral response
function input data” occurred, i.e. where the lower 8 bits of the processing_quality_flags have thevalue “18”.
number_of_convergence_error_occurrences

0 (static)

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Number of ground pixels where processing error “the main algorithm did not converge” occurred, i.e. where
the lower 8 bits of the processing_quality_flags have the value “19”.
number_of_cloud_filter_convergence_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “the cloud filter did not converge” occurred, i.e. where thelower 8 bits of the processing_quality_flags have the value “20”.
number_of_max_iteration_convergence_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “no convergence because retrieval exceeds maximum
number of iterations. Maximum value from configuration” occurred, i.e. where the lower 8 bits of theprocessing_quality_flags have the value “21”.
number_of_aot_lower_boundary_convergence_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “no convergence because the aerosol optical thickness
crosses lower boundary twice in succession” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “22”.
number_of_other_boundary_convergence_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “no convergence because a state vector element crosses
boundary twice in succession. Note that a separate failure flag is defined for non-convergence due tocrossing of lower AOT boundary” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “23”.
number_of_geolocation_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “geolocation out of range” occurred, i.e. where the lower 8
bits of the processing_quality_flags have the value “24”.
number_of_ch4_noscat_zero_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “the CH4 column retrieved by the non-scattering CO
algorithm from the weak band or strong band is 0” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “25”.
number_of_h2o_noscat_zero_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “the H2 O column retrieved by the non-scattering CO
algorithm from the weak band or strong band is 0” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “26”.
number_of_max_optical_thickness_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “maximum optical thickness exceeded during iterations”
occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “27”.
number_of_aerosol_boundary_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “boundary hit of aerosol parameters at last iteration”
occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “28”.
number_of_boundary_hit_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “fatal boundary hit during iterations” occurred, i.e. where
the lower 8 bits of the processing_quality_flags have the value “29”.

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0 (static)

NC_INT

Number of ground pixels where processing error “χ 2 is not-a-number or larger than 1010 ” occurred, i.e.
where the lower 8 bits of the processing_quality_flags have the value “30”.
number_of_svd_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “singular value decomposition failure” occurred, i.e. where
the lower 8 bits of the processing_quality_flags have the value “31”.
number_of_dfs_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “degree of freedom is not-a-number” occurred, i.e. where
the lower 8 bits of the processing_quality_flags have the value “32”.
number_of_radiative_transfer_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “errors occurred during the radiative transfer computations,no processing possible” occurred, i.e. where the lower 8 bits of the processing_quality_flags havethe value “33”.
number_of_optimal_estimation_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “errors occurred during the optimal estimation, processing
has been terminated” occurred, i.e. where the lower 8 bits of the processing_quality_flags have thevalue “34”.
number_of_profile_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “flag that indicates if there were any errors during thecomputation of the ozone profile” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “35”.
number_of_cloud_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “no cloud data” occurred, i.e. where the lower 8 bits of theprocessing_quality_flags have the value “36”.
number_of_model_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “forward model failure” occurred, i.e. where the lower 8
bits of the processing_quality_flags have the value “37”.
number_of_number_of_input_data_points_too_low_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “not enough input ozone columns to calculate a tropospheric column” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value“38”.
number_of_cloud_pressure_spread_too_low_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “cloud pressure variability to low to estimate a troposphericcolumn” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “39”.
number_of_cloud_too_low_level_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “clouds are too low in the atmosphere to assume sufficientshielding” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “40”.
number_of_generic_range_error_occurrences

0 (static)

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Number of ground pixels where processing error “generic range error” occurred, i.e. where the lower 8 bitsof the processing_quality_flags have the value “41”.
number_of_generic_exception_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “catch all generic error” occurred, i.e. where the lower 8
bits of the processing_quality_flags have the value “42”.
number_of_input_spectrum_alignment_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “input radiance and irradiance spectra are not aligned
correctly” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “43”.
number_of_abort_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “not processed because processor aborted prematurely(time out or user abort” occurred, i.e. where the lower 8 bits of the processing_quality_flags havethe value “44”.
number_of_wrong_input_type_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “wrong input type error, mismatch between expectation
and received data” occurred, i.e. where the lower 8 bits of the processing_quality_flags have thevalue “45”.
number_of_wavelength_calibration_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “an error occurred in the wavelength calibration of thispixe” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “46”.
number_of_coregistration_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “no colocated pixels found in a supporting ban” occurred,
i.e. where the lower 8 bits of the processing_quality_flags have the value “47”.
number_of_slant_column_density_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “slant column fit returned error, no values can be compute”
occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “48”.
number_of_airmass_factor_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “airmass factor could not be compute” occurred, i.e. where
the lower 8 bits of the processing_quality_flags have the value “49”.
number_of_vertical_column_density_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “vertical column density could not be compute” occurred,
i.e. where the lower 8 bits of the processing_quality_flags have the value “50”.
number_of_signal_to_noise_ratio_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “the signal to noise ratio for this spectrum is too low forprocessin” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “51”.
number_of_configuration_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “error while parsing the configuratio” occurred, i.e. where
the lower 8 bits of the processing_quality_flags have the value “52”.
number_of_key_error_occurrences

0 (static)

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Number of ground pixels where processing error “key does not exis” occurred, i.e. where the lower 8 bits ofthe processing_quality_flags have the value “53”.
number_of_saturation_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “saturation in input spectru” occurred, i.e. where the lower
8 bits of the processing_quality_flags have the value “54”.
number_of_max_num_outlier_exceeded_error_occurrences

0 (static)

NC_INT

Number of ground pixels where processing error “the number of outliers detected in the DOAS fit exceeds amaximum set for healthy spectra.” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “55”.
number_of_solar_eclipse_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “solar eclipse” occurred, i.e. where the lower 8 bits of theprocessing_quality_flags have the value “64”.
number_of_cloud_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “the cloud filter triggered causing the pixel to be skipped” occurred,
i.e. where the lower 8 bits of the processing_quality_flags have the value “65”.
number_of_altitude_consistency_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “too large difference between ECMWF altitude and DEM altitude
value” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “66”.
number_of_altitude_roughness_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “too large standard deviation of altitude in DEM” occurred, i.e.
where the lower 8 bits of the processing_quality_flags have the value “67”.
number_of_sun_glint_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “for pixels over water, viewing direction inside sun glint region.
Definition of sun glint angle and threshold value from ATBD” occurred, i.e. where the lower 8 bits of theprocessing_quality_flags have the value “68”.
number_of_mixed_surface_type_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “pixel contains land and water areas (e.g. coastal pixel)” occurred,
i.e. where the lower 8 bits of the processing_quality_flags have the value “69”.
number_of_snow_ice_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “pixel contains snow/ice: Snow/ice flag according to dynamic
input OR climatological surface albedo at VIS wavelength is larger than 0.5” occurred, i.e. where the lower
8 bits of the processing_quality_flags have the value “70”.
number_of_aai_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “aAI smaller than 2.0” occurred, i.e. where the lower 8 bits of theprocessing_quality_flags have the value “71”.
number_of_cloud_fraction_fresco_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “pixel contains clouds: The FRESCO effective cloud fraction is larger than threshold. Threshold value from ATBD” occurred, i.e. where the lower 8 bits of theprocessing_quality_flags have the value “72”.
number_of_aai_scene_albedo_filter_occurrences

0 (static)

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Number of ground pixels where input filter “pixel contains clouds: The difference between scene albedo at
380 nm from AAI calculation and the climatologcal surface albedo exceeds threshold. Threshold value from
ATBD. This test filters out clouds” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “73”.
number_of_small_pixel_radiance_std_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “pixel contains clouds: Standard deviation of radiances insmall-pixel column exceeds threshold. Threshold value from ATBD” occurred, i.e. where the lower 8 bits ofthe processing_quality_flags have the value “74”.
number_of_cloud_fraction_viirs_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “pixel contains clouds: The cloud fraction from VIIRS / NPP
exceeds theshold. Threshold value from ATBD” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “75”.
number_of_cirrus_reflectance_viirs_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “pixel contains clouds: Cirrus reflectance from VIIRS / NPP
exceeds threshold. Threshold value from ATBD” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “76”.
number_of_cf_viirs_swir_ifov_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “fraction of cloudy VIIRS pixels wihtin S5P SWIR ground pixel
exceeds a priori threshold from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “77”.
number_of_cf_viirs_swir_ofova_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “fraction of cloudy VIIRS pixels wihtin S5P SWIR OFOVa exceeds
a priori threshold from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “78”.
number_of_cf_viirs_swir_ofovb_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “fraction of cloudy VIIRS pixels wihtin S5P SWIR OFOVb exceeds
a priori threshold from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “79”.
number_of_cf_viirs_swir_ofovc_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “fraction of cloudy VIIRS pixels wihtin S5P SWIR OFOVc exceeds
a priori threshold from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “80”.
number_of_cf_viirs_nir_ifov_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “fraction of cloudy VIIRS pixels wihtin S5P NIR ground pixel
exceeds a priori threshold from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “81”.
number_of_cf_viirs_nir_ofova_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “fraction of cloudy VIIRS pixels wihtin S5P NIR OFOVa exceeds
a priori threshold from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “82”.
number_of_cf_viirs_nir_ofovb_filter_occurrences

0 (static)

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Number of ground pixels where input filter “fraction of cloudy VIIRS pixels wihtin S5P NIR OFOVb exceeds
a priori threshold from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “83”.
number_of_cf_viirs_nir_ofovc_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “fraction of cloudy VIIRS pixels wihtin S5P NIR OFOVc exceeds
a priori threshold from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “84”.
number_of_refl_cirrus_viirs_swir_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “average VIIRS cirrus reflectance within SWIR ground pixel
exceeds a priori threshold from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “85”.
number_of_refl_cirrus_viirs_nir_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “average VIIRS cirrus reflectance within NIR ground pixel exceeds
a priori threshold from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “86”.
number_of_diff_refl_cirrus_viirs_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “difference in VIIRS average cirrus reflectance between SWIR
and NIR ground pixel exceeds a priori threshold from configuration” occurred, i.e. where the lower 8 bits ofthe processing_quality_flags have the value “87”.
number_of_ch4_noscat_ratio_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “the ratio between [CH4 ]weak and [CH4 ]strong is below or exceeds
a priori thresholds from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “88”.
number_of_ch4_noscat_ratio_std_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “the standard deviation of [CH4 ]weak /[CH4 ]strong within the SWIR
pixel and the 8 neighbouring pixels exceeds a priori threshold from configuration” occurred, i.e. where thelower 8 bits of the processing_quality_flags have the value “89”.
number_of_h2o_noscat_ratio_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “the ratio between [H2 O ]weak and [H2 O ]strong is below or exceeds
a priori thresholds from configuration” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value “90”.
number_of_h2o_noscat_ratio_std_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “the standard deviation of [H2 O ]weak /[H2 O ]strong within the SWIR
pixel and the 8 neigbouring pixels exceeds a priori threshold from configuration” occurred, i.e. where thelower 8 bits of the processing_quality_flags have the value “91”.
number_of_diff_psurf_fresco_ecmwf_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “difference between the FRESCO apparent surface pressure andthe ECMWF surface pressure exceeds a priori threshold from configuration” occurred, i.e. where the lower
8 bits of the processing_quality_flags have the value “92”.
number_of_psurf_fresco_stdv_filter_occurrences

0 (static)

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Number of ground pixels where input filter “the standard deviation of the FRESCO apparent surface pressurein the NIR pixel and the 8 surrounding pixels exceeds a priori threshold from configuration” occurred, i.e.
where the lower 8 bits of the processing_quality_flags have the value “93”.
number_of_ocean_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “the ground pixel is over ocean (and ocean glint retrievals are notswitched on)” occurred, i.e. where the lower 8 bits of the processing_quality_flags have the value“94”.
number_of_time_range_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “time is out of the range that is to be processed” occurred, i.e.
where the lower 8 bits of the processing_quality_flags have the value “95”.
number_of_pixel_or_scanline_index_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “not processed because pixel index does not match general
selection criteria” occurred, i.e. where the lower 8 bits of the processing_quality_flags have thevalue “96”.
number_of_geographic_region_filter_occurrences

0 (static)

NC_INT

Number of ground pixels where input filter “pixel falls outside the specified regions of interest” occurred, i.e.
where the lower 8 bits of the processing_quality_flags have the value “97”.
number_of_input_spectrum_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “number of good pixels in radiance, irradiance or
calculated reflectance below threshold from configuration” occurred, i.e. where bit 8 in the processing_quality_flags is set to “1”.
number_of_wavelength_calibration_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “offset from wavelength fit is larger than limit set inconfiguration” occurred, i.e. where bit 9 in the processing_quality_flags is set to “1”.
number_of_extrapolation_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “pressure or temperature outside cross section LUT
range, other lookup table extrapolation” occurred, i.e. where bit 10 in the processing_quality_flags
is set to “1”.
number_of_sun_glint_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “sun glint posibility warning” occurred, i.e. where bit 11
in the processing_quality_flags is set to “1”.
number_of_south_atlantic_anomaly_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “tROPOMI is inside the south Atlantic anomaly while
taking these measurements” occurred, i.e. where bit 12 in the processing_quality_flags is set to “1”.
number_of_sun_glint_correction_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “a sun glint correction has been applied” occurred, i.e.
where bit 13 in the processing_quality_flags is set to “1”.
number_of_snow_ice_warning_occurrences

0 (static)

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Number of ground pixels where processing warning “snow/ice flag is set, i.e. using scene data from thecloud support product” occurred, i.e. where bit 14 in the processing_quality_flags is set to “1”.
number_of_cloud_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “cloud filter based on FRESCO apparent surfacepressure (VIIRS not available), cloud fraction above threshold or cloud pressure adjusted to force cloud
above surface. In case of Cloud product this flag indicates the possiblity of ice-clouds” occurred, i.e. where
bit 15 in the processing_quality_flags is set to “1”.
number_of_AAI_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “possible aerosol contamination as either indicated by
the AAI (O3 profile)” occurred, i.e. where bit 16 in the processing_quality_flags is set to “1”.
number_of_pixel_level_input_data_missing_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “dynamic auxiliary input data (e.g.. cloud) is missing forthis ground pixel. A fallback option is used” occurred, i.e. where bit 17 in the processing_quality_flags is set to “1”.
number_of_data_range_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “carbon monoxide column tends to negative values;
Water column tends to negative values; Heavy water (HDO) column tends to negative values; others. In
case of the O3 product this flag indicates VCD or effective albedo values outside a valid range. In caseof the SO2 or the HCHO product this flag indicates AMF values outside a valid range. For O3 profile thiswarning indicates an out of range cost function, or an out of range RMS difference between retrieval and apriori” occurred, i.e. where bit 18 in the processing_quality_flags is set to “1”.
number_of_low_cloud_fraction_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “low cloud fraction, therefore no cloud pressure retrieved”
occurred, i.e. where bit 19 in the processing_quality_flags is set to “1”.
number_of_altitude_consistency_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “difference between ECMWF surface elevation andhigh-resolution surface elevation exceeds threshold from configuration” occurred, i.e. where bit 20 in theprocessing_quality_flags is set to “1”.
number_of_signal_to_noise_ratio_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “signal to noise ratio in SWIR and/or NIR band below
threshold from configuration. For the O3 and HCHO products this flag indicates an RMS above a certain
threshold” occurred, i.e. where bit 21 in the processing_quality_flags is set to “1”.
number_of_deconvolution_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “failed deconvolution irradiance spectrum (not pixelspecific, but row-specific)” occurred, i.e. where bit 22 in the processing_quality_flags is set to“1”.
number_of_so2_volcanic_origin_likely_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “warning for SO2 BL product, UTLS products: volcanic
origin except for heavily polluted sites. For O3 profile this warning is issued in case of a large SO2 column
which has an impact on the O3 profile retrieval” occurred, i.e. where bit 23 in the processing_quality_flags is set to “1”.

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0 (static)

NC_INT

Number of ground pixels where processing warning “warning for SO2 BL product, UTLS products: volcanic
origin certain” occurred, i.e. where bit 24 in the processing_quality_flags is set to “1”.
number_of_interpolation_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “warning for interpolation on partially missing data. In
this case the valid available data is used, potentially leading to a bias” occurred, i.e. where bit 25 in theprocessing_quality_flags is set to “1”.
number_of_saturation_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “saturation occurred spectrum, possibly causing biases
in the retrieval” occurred, i.e. where bit 26 in the processing_quality_flags is set to “1”.
number_of_high_sza_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “warning for high solar zenith angle. In this case,the processing can be performed with less final quality” occurred, i.e. where bit 27 in the processing_quality_flags is set to “1”.
number_of_cloud_retrieval_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “warning occurring when the retrieval diagnostic
indicates a degraded quality of the cloud retrieval” occurred, i.e. where bit 28 in the processing_quality_flags is set to “1”.
number_of_cloud_inhomogeneity_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “the cloud coregistration inhomogeneity parameter isabove a given threshold. This warning is also set when the coregistration weight sums are less than 1”
occurred, i.e. where bit 29 in the processing_quality_flags is set to “1”.
number_of_thermal_instability_warning_occurrences

0 (static)

NC_INT

Number of ground pixels where processing warning “input spectra have been labeled with a thermal
instability warning flag” occurred, i.e. where bit 30 in the processing_quality_flags is set to “1”.
global_processing_warnings‘None’ (static)

NC_STRING

All warning messages, separated by newlines, with duplicates removed.
time_for_algorithm_initialization-1.0 (static)

NC_DOUBLE

Time in seconds needed for initialization.
time_for_processing-1.0 (static)

NC_DOUBLE

Time in seconds needed for processing.
time_per_pixel-1.0 (static)

NC_DOUBLE

Time per pixel in seconds needed for processing.
time_standard_deviation_per_pixel-1.0 (static)Standard deviation of the time per pixel in seconds needed for processing.
Dimensions in AER_AI/METADATA/QA_STATISTICS
vertices For the histogram boundaries.
size 2 (fixed)

NC_DOUBLE

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aerosol_index_354_388_histogram_axis Histogram axis.
size 100 (fixed)
aerosol_index_354_388_pdf_axis Probability density function axis.
size 400 (fixed)
aerosol_index_340_380_histogram_axis Histogram axis.
size 100 (fixed)
aerosol_index_340_380_pdf_axis Probability density function axis.
size 400 (fixed)
aerosol_index_335_367_histogram_axis Histogram axis.
size 100 (fixed)
aerosol_index_335_367_pdf_axis Probability density function axis.
size 400 (fixed)
Variables in AER_AI/METADATA/QA_STATISTICS
aerosol_index_354_388_histogram_axis in AER_AI/METADATA/QA_STATISTICS
Description:

Horizontal axis for the histograms of the aerosol indices.

Dimensions:aerosol_index_354_388_histogram_axis (coordinate variable).

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (dynamic)

NC_STRING

Same unit as the main parameter. This attribute originates from the CF standard.
comment‘Histogram axis of the aerosol index’ (static)

long_name‘Histogram axis of the aerosol index’ (static)

NC_STRING

bounds‘aerosol_index_354_388_histogram_bounds’(static)

NC_STRING

NC_STRING

aerosol_index_354_388_pdf_axis in AER_AI/METADATA/QA_STATISTICS
Description:

Horizontal axis for the probability distribution functions of aerosol index.

Dimensions:aerosol_index_354_388_pdf_axis (coordinate variable).

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (dynamic)

NC_STRING

Same unit as the main parameter. This attribute originates from the CF standard.
comment‘Probability density function of the aerosol index’(static)

NC_STRING

long_name‘Probability density function of the aerosol index’(static)

NC_STRING

bounds‘aerosol_index_pdf_bounds’ (static)

NC_STRING

aerosol_index_354_388_histogram_bounds in AER_AI/METADATA/QA_STATISTICS
Dimensions:aerosol_index_354_388_histogram_axis, vertices.

Type:

NC_FLOAT.

Source:Processor.

aerosol_index_354_388_pdf_bounds in AER_AI/METADATA/QA_STATISTICS
Dimensions:aerosol_index_354_388_pdf_axis, vertices.

Type:

NC_FLOAT.

Source:Processor.

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aerosol_index_340_380_histogram_axis in AER_AI/METADATA/QA_STATISTICS
Description:

Horizontal axis for the histograms of the aerosol indices.

Dimensions:aerosol_index_340_380_histogram_axis (coordinate variable).

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (dynamic)

NC_STRING

Same unit as the main parameter. This attribute originates from the CF standard.
comment‘Histogram axis of the aerosol index’ (static)

NC_STRING

long_name‘Histogram axis of the aerosol index’ (static)

NC_STRING

bounds‘aerosol_index_340_380_histogram_bounds’(static)

NC_STRING

aerosol_index_340_380_pdf_axis in AER_AI/METADATA/QA_STATISTICS
Description:

Horizontal axis for the probability distribution functions of aerosol index.

Dimensions:aerosol_index_340_380_pdf_axis (coordinate variable).

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (dynamic)

NC_STRING

Same unit as the main parameter. This attribute originates from the CF standard.
comment‘Probability density function of the aerosol index’(static)

NC_STRING

long_name‘Probability density function of the aerosol index’(static)

NC_STRING

bounds‘aerosol_index_pdf_bounds’ (static)

NC_STRING

aerosol_index_340_380_histogram_bounds in AER_AI/METADATA/QA_STATISTICS
Dimensions:aerosol_index_340_380_histogram_axis, vertices.

Type:

NC_FLOAT.

Source:Processor.

aerosol_index_340_380_pdf_bounds in AER_AI/METADATA/QA_STATISTICS
Dimensions:aerosol_index_340_380_pdf_axis, vertices.

Type:

NC_FLOAT.

Source:Processor.

aerosol_index_335_367_histogram_axis in AER_AI/METADATA/QA_STATISTICS
Description:

Horizontal axis for the histograms of the aerosol indices.

Dimensions:aerosol_index_335_367_histogram_axis (coordinate variable).

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (dynamic)

NC_STRING

Same unit as the main parameter. This attribute originates from the CF standard.
comment‘Histogram axis of the aerosol index’ (static)

long_name‘Histogram axis of the aerosol index’ (static)

NC_STRING

bounds‘aerosol_index_335_367_histogram_bounds’(static)

NC_STRING

aerosol_index_335_367_pdf_axis in AER_AI/METADATA/QA_STATISTICS
Description:

Horizontal axis for the probability distribution functions of aerosol index.

Dimensions:aerosol_index_335_367_pdf_axis (coordinate variable).

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Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

units

‘1’ (dynamic)

NC_STRING

Same unit as the main parameter. This attribute originates from the CF standard.
comment‘Probability density function of the aerosol index’(static)

NC_STRING

long_name‘Probability density function of the aerosol index’(static)

NC_STRING

bounds‘aerosol_index_pdf_bounds’ (static)

NC_STRING

aerosol_index_335_367_histogram_bounds in AER_AI/METADATA/QA_STATISTICS
Dimensions:aerosol_index_335_367_histogram_axis, vertices.

Type:

NC_FLOAT.

Source:Processor.

aerosol_index_335_367_pdf_bounds in AER_AI/METADATA/QA_STATISTICS
Dimensions:aerosol_index_335_367_pdf_axis, vertices.

Type:

NC_FLOAT.

Source:Processor.

aerosol_index_354_388_histogram in AER_AI/METADATA/QA_STATISTICS
Description:

Histogram of the aerosol index from the 354/388 nm wavelength pair in the current granule.

Dimensions:aerosol_index_340_380_histogram_axis.

Type:

NC_INT.

Source:Processor.

Attributes:

Name

Value

Type

comment‘Histogram of the aerosol index of the 354/388 nm
pair in the current granule’ (static)

NC_STRING

number_of_overflow_values

0 (dynamic)

NC_INT

The number of encountered values that are larger than the top of the histogram.
number_of_underflow_values

0 (dynamic)

NC_INT

The number of encountered values that are smaller than the base of the histogram.
aerosol_index_340_380_histogram in AER_AI/METADATA/QA_STATISTICS
Description:

Histogram of the aerosol index from the 340/380 nm wavelength pair in the current granule.

Dimensions:aerosol_index_340_380_histogram_axis.

Type:

NC_INT.

Source:Processor.

Attributes:

Name

Value

Type

comment‘Histogram of the aerosol index of the 340/380 nm
pair in the current granule’ (static)

NC_STRING

number_of_overflow_values

0 (dynamic)

NC_INT

The number of encountered values that are larger than the top of the histogram.
number_of_underflow_values

0 (dynamic)

NC_INT

The number of encountered values that are smaller than the base of the histogram.
aerosol_index_335_367_histogram in AER_AI/METADATA/QA_STATISTICS
Description:

Histogram of the aerosol index from the 335/367 nm wavelength pair in the current granule.

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Dimensions:aerosol_index_340_380_histogram_axis.

Type:

NC_INT.

Source:Processor.

Attributes:

Name

Value

Type

comment‘Histogram of the aerosol index of the 354/388 nm
pair in the current granule’ (static)

NC_STRING

number_of_overflow_values

0 (dynamic)

NC_INT

The number of encountered values that are larger than the top of the histogram.
number_of_underflow_values

0 (dynamic)

NC_INT

The number of encountered values that are smaller than the base of the histogram.
aerosol_index_354_388_pdf in AER_AI/METADATA/QA_STATISTICS
Description:

Probability density function of the aerosol index from the 354/388 nm wavelength pair inthe current granule. The values are weighted with cos(δgeo ) and spread out using the error
estimate.

Dimensions:aerosol_index_354_388_pdf_axis.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

comment‘Probability density function of the aerosol index of
the 354/388 nm pair in the current granule’ (static)

NC_STRING

geolocation_sampling_total

0 (static)

NC_FLOAT

The sum of cosine values of latitudes from the pixels that were used in the pdf.
aerosol_index_340_380_pdf in AER_AI/METADATA/QA_STATISTICS
Description:

Probability density function of the aerosol index from the 340/380 nm wavelength pair inthe current granule. The values are weighted with cos(δgeo ) and spread out using the error
estimate.

Dimensions:aerosol_index_340_380_pdf_axis.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

comment‘Probability density function of the aerosol index of
the 340/380 nm pair in the current granule’ (static)

NC_STRING

geolocation_sampling_total

0 (static)

NC_FLOAT

The sum of cosine values of latitudes from the pixels that were used in the pdf.
aerosol_index_335_367_pdf in AER_AI/METADATA/QA_STATISTICS
Description:

Probability density function of the aerosol index from the 335/367 nm wavelength pair inthe current granule. The values are weighted with cos(δgeo ) and spread out using the error
estimate.

Dimensions:aerosol_index_335_367_pdf_axis.

Type:

NC_FLOAT.

Source:Processor.

Attributes:

Name

Value

Type

comment‘Probability density function of the aerosol index of
the 335/367 nm pair in the current granule’ (static)

NC_STRING

geolocation_sampling_total

0 (static)

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The sum of cosine values of latitudes from the pixels that were used in the pdf.

10.2.2

Group “ALGORITHM_SETTINGS” in “METADATA”

The algorithm settings are attached as attributes to this group. The current settings are listed here, each itemin the list is a string attribute.
Configurations in AER_AI/METADATA/ALGORITHM_SETTINGS
configuration.version.framework 1.2.0
Allow the framework to verify that the configuration file is up to date.
configuration.version.algorithm 1.4.0
Allow the processor to verify that the configuration file is up to date.
processing.algorithm AER_AI
Define the algorithm that is to be loaded.
input.count 1
Define the number of input files.
input.1.type L1B_RA_BD3
Define the input type (band) for the first input.
input.1.irrType L1B_IR_UVN
Define which irradiance accompanies the first input.
input.1.band 3
Which band is this (for selecting the irradiance and coregistration to output).
output.count 1
Define the number of output products
output.useFletcher32 true
Boolean to indicate status of Fletcher32 filter (default is on).
output.useCompression true
Boolean to set status of comression (default is on).
output.useShuffleFilter true
Boolean to set status of shuffle filter (default is on).
output.compressionLevel 3
Integer value to set compression level, default is 3.
output.1.type L2__AER_AI
Output product short name.
output.1.config product.AER_AI.xml
Output product specification.
output.1.band 3
Geolocation in output follows this band.
algo.n_pair 3
The number of aerosol index pairs.
algo.algorithm_variant 1
Several algorithm variants are included in the code, this keys selects the variant that is used. Number 1
is nominal (and recommended). Here a wavelength band is used and a triangular weighting is used.
algo.pair_1.id TOMS_pair
Identifier for the first aerosol index pair.
algo.pair_1.wavelength_1 340
Shortest wavelength of the first aerosol index pair, in nm.
algo.pair_1.wavelength_2 380
Longest wavelength of the first aerosol index pair, in nm.
algo.pair_1.delta_wavelength 2.0
The width of the wavelength band for selecting pixels for index pair number 1. Not used in algorithm
variant 1.
algo.pair_1.number_spectral_pixels 7
The number of spectral pixels used for calculating the reflectance for index pair number 1.
algo.pair_1.min_wavelength 1
The minimum number of spectral pixels before we declare a complete failure for index pair number 1.

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algo.pair_1.radiance_correction_factor_1 1.0
Multiplication factor for the radiance at wavelength 1 of pair 1 (340 nm).
algo.pair_1.radiance_correction_factor_2 1.0
Multiplication factor for the radiance at wavelength 2 of pair 1 (380 nm).
algo.pair_1.aai_add_offset -1.05
Additive offset for the AAI value of pair 1 (340/380 nm).
algo.pair_2.id OMI_pair
Identifier for the second aerosol index pair.
algo.pair_2.wavelength_1 354
Shortest wavelength of the second aerosol index pair, in nm.
algo.pair_2.wavelength_2 388
Longest wavelength of the second aerosol index pair, in nm.
algo.pair_2.delta_wavelength 2.0
The width of the wavelength band for selecting pixels for index pair number 2, not used in algorithm
variant 1.
algo.pair_2.number_spectral_pixels 7
The number of spectral pixels used for calculating the reflectance for index pair number 2.
algo.pair_2.min_wavelength 1
The minimum number of spectral pixels before we declare a complete failure for index pair number 2.
algo.pair_2.radiance_correction_factor_1 1.0
Multiplication factor for the radiance at wavelength 1 of pair 2 (354 nm).
algo.pair_2.radiance_correction_factor_2 1.0
Multiplication factor for the radiance at wavelength 2 of pair 2 (388 nm).
algo.pair_2.aai_add_offset -0.85
Additive offset for the AAI value of pair 2 (354/388 nm).
algo.pair_3.id TOMS-EP_pairalgo.pair_3.wavelength_1 335
algo.pair_3.wavelength_2 367
algo.pair_3.delta_wavelength 4.0
algo.pair_3.number_spectral_pixels 13
algo.pair_3.min_wavelength 1
algo.pair_3.radiance_correction_factor_1 1.0
algo.pair_3.radiance_correction_factor_2 1.0
algo.pair_3.aai_add_offset -1.1
processing.vzaMin 0.0
The minimum viewing zenith angle.
processing.vzaMax 78.0
The maximum viewing zenith angle.
processing.szaMin 0.0
The minimum solar zenith angle.
processing.szaMax 88.0
The maximum solar zenith angle.
processing.groupDem DEM_RADIUS_05000
Which DEM to use.
processing.correct_surface_pressure_for_altitude true
Flag to control the correction of the surface pressure for local orography. Default is true.
processing.ignore_pixel_flags False
When set to ‘True’, the pixel quality flags are ignored. When set to ‘False’, only pixels where none of theflags are set will be used in processing.
processing.exclude_flags 4294967295
output.histogram.aerosol_index_340_380.start -6
Start value for the histogram of the aerosol index from the TOMS pair.
output.histogram.aerosol_index_340_380.end 14
End value for the histogram of the aerosol index from the TOMS pair.
output.histogram.aerosol_index_354_388.start -6
Start value for the histogram of the aerosol index from the OMI pair.
output.histogram.aerosol_index_354_388.end 14
End value for the histogram of the aerosol index from the OMI pair.

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output.histogram.aerosol_index_335_367.start -6
output.histogram.aerosol_index_335_367.end 14
processing.signal_to_noise.test yes
lag pixels when signal to noise ratio is below threshold. Default no testing, unless processing.signal_to_noise.window.range is set.
processing.signal_to_noise.window.range 350.0, 355.0
avelength pixel range for testing signal to noise ratio. Default range is all wavelengts, but only if
processing.signal_to_noise.test is set
processing.signal_to_noise.threshold 12
Threshold value for signal to noise ratio, in decibel. Ground-pixel is flagged when majority wavelength
pixels has signal to noise below threshold. Default is 12.
processing.radiancePixelsMinError 2
inumum number of valid spectral pixels required for processing ground-pixel. With less pixels a PQF_E_INPUT_SPECTRUM_MISSING is generated.
processing.radiancePixelsMinWarning 7
ith less valid spectral pixels a PQF_W_INPUT_SPECTRUM_WARNING is generated. The ground-pixel
can still be processed.
wavelength_calibration.perform_wavelength_fit yes
Master switch for the wavelength calibration.
wavelength_calibration.window 330.0, 390.0
The wavelength calibration window. This must contain all wavelengths in the algorithm, i.e. 340 – 388,
with a margin.
wavelength_calibration.rad.polynomial_order 3
wavelength_calibration.irr.polynomial_order 2
wavelength_calibration.include_stretch no
For aerosol index we do not include a stretch/squeeze parameter.
wavelength_calibration.rad.include_ring yes
wavelength_calibration.irr.include_ring nowavelength_calibration.initial_guess.a0 1.0
Initial guess for the parameters of the polynomial in the wavelength fit. 1, 0.1, 0.01, 0.01, . . . for a0, a1,
a2, a3, . . . as appropriate.
wavelength_calibration.initial_guess.a1 0.1
wavelength_calibration.initial_guess.a2 0.01
wavelength_calibration.initial_guess.shift 0.0
Initial guess for the wavelength shift.
wavelength_calibration.initial_guess.ring 0.06
Initial guess for the Ring coefficient.
wavelength_calibration.initial_guess.stretch 0.0
Initial guess for the strech parameter.
wavelength_calibration.sigma.a0 1.0
a priori precision of the polynomial coefficients. 1, 0.1, 0.1, 0.1, . . . for a0, a1, a2, a3, . . . as appropriate.
wavelength_calibration.sigma.a1 0.1
wavelength_calibration.sigma.shift 3.0
a priori precision of the wavelength shift. Set to the spectral sampling for band 3 divided by 3.
wavelength_calibration.sigma.ring 0.06
a priori precision of the Ring coefficient.
wavelength_calibration.sigma.stretch 0.07
a priori precision of the strech parameter. Due to scaling equal to pixel size scaling at end of window.
wavelength_calibration.max_iterations 12
The maximum number of iterations for the wavelength fit.
wavelength_calibration.irr.max_iterations 20
wavelength_calibration.convergence_threshold 1.0
Convergence criterium (auto scaled).
qa_value.input_spectrum_warning 70.0
he qa_value multiplication factor (in percent) for when the number of pixels in the input spectrum is below
nominal.
qa_value.wavelength_calibration_warning 90.0
he qa_value multiplication factor (in percent) for when the wavelength calibration offset is larger than a

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configured threshold.
qa_value.extrapolation_warning 100.0
he qa_value multiplication factor (in percent) for when extrapolation was used in the retrieval.
qa_value.sun_glint_warning 70.0
he qa_value multiplication factor (in percent) for when the pixel is potentially affected by sun glint.
qa_value.south_atlantic_anomaly_warning 100.0
he qa_value multiplication factor (in percent) for when the instrument was flying through the South Atlantic
Anomaly while taking this measurement.
qa_value.sun_glint_correction 100.0
he qa_value multiplication factor (in percent) for when the cloud fraction was corrected for sun glint.
qa_value.snow_ice_warning 100.0
he qa_value multiplication factor (in percent) for when the snow_ice_warning flag is raised.
qa_value.cloud_warning 100.0
he qa_value multiplication factor (in percent) for when the cloud_warning flag is raised.
qa_value.AAI_warning 100.0
he qa_value multiplication factor (in percent) for when the AAI_warning flag is raised.
qa_value.pixel_level_input_data_missing 80.0
he qa_value multiplication factor (in percent) for when the pixel_level_input_data_missing flag is raised.
qa_value.data_range_warning 100.0
he qa_value multiplication factor (in percent) for when the data_range_warning flag is raised.
qa_value.low_cloud_fraction_warning 100.0
he qa_value multiplication factor (in percent) for when the low_cloud_fraction_warning flag is raised.
qa_value.altitude_consistency_warning 100.0
he qa_value multiplication factor (in percent) for when the altitude_consistency_warning flag is raised.
qa_value.signal_to_noise_ratio_warning 100.0
he qa_value multiplication factor (in percent) for when the signal_to_noise_ratio_warning flag is raised.
qa_value.deconvolution_warning 100.0
he qa_value multiplication factor (in percent) for when the deconvolution_warning flag is raised.
qa_value.so2_volcanic_origin_likely_warning 100.0
he qa_value multiplication factor (in percent) for when the so2_volcanic_origin_likely_warning flag israised.
qa_value.so2_volcanic_origin_certain_warning 100.0
he qa_value multiplication factor (in percent) for when the so2_volcanic_origin_certain_warning flag israised.
qa_value.interpolation_warning 100.0
he qa_value multiplication factor (in percent) for when the interpolation_warning flag is raised.
qa_value.thermal_instability_warning 100.0
he qa_value multiplication factor (in percent) for when the thermal_instability_warning flag is raised.
quality_control.qa_value.limit 0.5
f the maximum qa_value in the granule is smaller than this limit, then a warning shall be issued. Default= 0.5
quality_control.missing_input.max_fraction 0.25
If the fraction of successfully processed pixels that has a pixel level input data missing warning attached
it exceeds this fraction, then a warning will be issued. Default = 0.5
quality_control.success.min_fraction 0.001
If the fraction of succesfully processed pixels is smaller than this limit, then a warning will be issued.
Default = 0.001
10.2.3

Group “GRANULE_DESCRIPTION” in “METADATA”

Common granule level metadata.
Attributes in AER_AI/METADATA/GRANULE_DESCRIPTIONGroup attributes attached to GRANULE_DESCRIPTION
Name
GranuleStart

Value

Type
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Start of the granule as ISO date/time string in UTC: YYYY -MM-DDTHH:MM:SS.mmmmmmZ. The formal
definition of ISO date/time strings is given in [RD34].
GranuleEnd

NC_STRING

End of the granule as ISO date/time string in UTC: YYYY -MM-DDTHH:MM:SS.mmmmmmZ. The formal
definition of ISO date/time strings is given in [RD34].
InstrumentName‘TROPOMI’ (static)

NC_STRING

The name of the instrument, fixed to “TROPOMI”.
MissionName‘Sentinel-5 precursor’ (static)

NC_STRING

The name of the mission, fixed to “Sentinel-5 precursor”.
MissionShortName‘S5P’ (static)

NC_STRING

The short name of the mission, fixed to “S5P”.
ProcessLevel‘2’ (static)

NC_STRING‘%(processingcenter)s’ (dynamic)

NC_STRING

This is a level 2 product.
ProcessingCenter

Where was the processor run? The source is the probably the joborder, the most likely value for operationaluse is “DLR/Oberpfaffenhofen”.
ProcessingNode

NC_STRING

The name of the machine that processed the data. This may aid in diagnosing failures in the processing.
ProcessorVersion‘%(version)s’ (dynamic)

NC_STRING

The version number of the processor used to produce the file. This is a string formatted as “major.minor.bugfix”.
ProductFormatVersion

1 (static)

NC_INTThe version of the format of the product file. This should be incremented whenever a datafield is added to
the files.
ProcessingMode

NC_STRING

This attribute indicates the mode of the processor.
Possible values: Near-realtime, Offline, Reprocessing, Test, SyntheticTest
LongitudeOfDaysideNadirEquatorCrossing

NC_FLOATThe longitude of the nadir-point at the day-side equator crossing. This gives a rough indication where theorbit is located. The value is calculated using an orbit propagator before the observation, so that a consisten
value is used for all processing stages.
CollectionIdentifier‘%(collection_identifier)s’ (dynamic)

NC_STRING

Identification of the processing collection, i.e. the group of products that can be used together as aconsistent data set.
ProductShortName‘L2__AER_AI’ (static)

NC_STRING

The short product name. For the aerosol index product this is fixed to “L2__AER_AI”.
10.2.3.1

Group “ISO_METADATA” in “iso_metadata”

Metadata that is structured following the ISO metadata standards [RD28, RD37], especially part 2. The
metadata in this group is structured using the methods from Level 1B, which is described in the Level 1B
metadata specification [RD33].
All “objectType” attributes indicate the XML object when generating an ISO 19139 [RD37] compliant
XML metadata file.
Note that this group is meant to be treated as a ‘black box’. The information is collected here so that it canbe extracted into XML side-files for ingestion into data search tools and metadata collections.
Attributes in AER_AI/METADATA/ISO_METADATAGroup attributes attached to ISO_METADATA
Name

Value

Type

gmd:dateStamp‘2015-10-16’ (static)

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Date of creation of the metadata, as ISO 8601 [RD34] string specifying year, month and day.
gmd:fileIdentifier‘urn:ogc:def:EOP:ESA:SENTINEL.S5P_TROP_%(shortname)s’ (dynamic)

NC_STRING

Unique identifier for metadata file, see the Level 1B metadata specification [RD33, table 5] for a discussionof the value.
Replace %(. . . )s with the “ProductShortName” value from the Level 2 “/METADATA/GRANULE_DESCRIPTION” metadata group.
gmd:hierarchyLevelName‘EO Product Collection’ (static)

NC_STRING

Name of the hierarchy levels for which the metadata is provided.
gmd:metadataStandardName‘ISO 19115-2 Geographic Information - Metadata Part
2 Extensions for imagery and gridded data’ (static)

NC_STRING

Name of the metadata standard.
gmd:metadataStandardVersion ‘ISO 19115-2:2009(E), S5P profile’ (static)

NC_STRING

Version (profile) of the metadata standard used.
objectType‘gmi:MI_Metadata’ (static)

NC_STRING

Name of the metadata class [RD33, table 5].
10.2.3.2

Group “gmd:language” in “ISO_METADATA”

Language used for the metadata, fixed to English.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:languageGroup attributes attached to gmd:language
Name

Value

Type

codeList‘http://www.loc.gov/standards/iso639-2/’ (static)

NC_STRING

codeListValue‘eng’ (static)

NC_STRING

objectType‘gmd:LanguageCode’ (static)

NC_STRING

10.2.3.3

Group “gmd:characterSet” in “ISO_METADATA”

The character encoding used for the metadata. This is fixed to UTF-8, but the climate and forecasting
conventions, version 1.6 limits this further to 7-bit ASCII (which is a subset of UTF-8).
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:characterSet
Group attributes attached to gmd:characterSet
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#MD_CharacterSetCode’ (static)

NC_STRING

codeListValue‘utf8’ (static)

NC_STRING

objectType‘gmd:MD_CharacterSetCode’ (static)

NC_STRING

10.2.3.4

Group “gmd:hierarchyLevel” in “ISO_METADATA”

Scope to wich metadata applies.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:hierarchyLevel
Group attributes attached to gmd:hierarchyLevel
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#MD_ScopeCode’ (static)

NC_STRING

codeListValue‘series’ (static)

NC_STRING

objectType‘gmd:MD_ScopeCode’ (static)

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Group “gmd:contact” in “ISO_METADATA”

Contact information for the product.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:contact
Group attributes attached to gmd:contact
Name

Value

Type

gmd:organisationName‘Copernicus Space Component Data Access System,
ESA, Services Coordinated Interface’ (static)

NC_STRING

objectType‘gmd:CI_ResponsibleParty’ (static)

NC_STRING

10.2.3.6

Group “gmd:contactInfo” in “gmd:contact”

The detailed contact information.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:contact/gmd:contactInfo
Group attributes attached to gmd:contactInfo
Name

Value

Type

objectType‘gmd:CI_Contact’ (static)

NC_STRING

10.2.3.7

Group “gmd:address” in “gmd:contactInfo”

The actual email address.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:contact/gmd:contactInfo/gmd:addressGroup attributes attached to gmd:address
Name

Value

Type

gmd:electronicMailAddress‘EOSupport@copernicus.esa.int’ (static)

NC_STRING

objectType‘gmd:CI_Address’ (static)

NC_STRING

10.2.3.8

Group “gmd:role” in “gmd:contact”

The role of the adress provided in this group.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:contact/gmd:role
Group attributes attached to gmd:role
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_RoleCode’ (static)

NC_STRING

codeListValue‘pointOfContact’ (static)

NC_STRING

objectType‘gmd:CI_RoleCode’ (static)

NC_STRING

10.2.3.9

Group “gmd:identificationInfo” in “ISO_METADATA”

Identification information contains information to uniquely identify the data. Identification information includes
information about the citation for the resource, an abstract, the purpose, credit, the status and points ofcontact. The MD_Identification entity is mandatory. The MD_Identification entity is specified (subclassed) as
MD_DataIdentification because in this case it is used to identify data.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo
Group attributes attached to gmd:identificationInfo
Name
gmd:abstract

Value

Type
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Brief narrative summary of the content of the resource. This is product specific, with modifications fortimeliness and and pixel size. The pixel size listed below are the “small” pixels, with a length of 5.5 km
in the flight direction for the main bands. For observations before August 6, 2019, the length in the flight
direction is 7 km. Ozone profile adds several pixels in the flight direction, and has an approximate pixel sizeof 30 × 30 km2 for the “small” pixels, and 35 × 30 km2 for the “large” pixels.
L2__AER_AI (KNMI) Aerosol index with a spatial resolution of 5.5 × 3.5 km2 observed at about 13:30 local
solar time from spectra measured by TROPOMI
L2__AER_LH (KNMI) Altitude of elevated aerosol layer for cloud-free observations with a spatial resolutionof 5.5 × 3.5 km2 observed at about 13:30 local solar time from spectra measured by TROPOMI
L2__NO2___ (KNMI) Nitrogen dioxide tropospheric column with a spatial resolution of 5.5 × 3.5 km2 observed at about 13:30 local solar time from spectra measured by TROPOMI
L2__O3__PR (KNMI) Ozone profile with a vertical resolution of 6 km and a horizontal resolution of
30 × 30 km2 observed at about 13:30 local solar time from spectra measured by TROPOMI
L2__CH4___ (SRON) Dry-air mixing ratio of methane for cloud-free observations with a spatial resolutionof 5.5 × 7 km2 observed at about 13:30 local solar time from spectra measured by TROPOMI
L2__CO____ (SRON) Carbon monoxide column with a spatial resolution of 5.5 × 7 km2 observed at about
13:30 local solar time from spectra measured by TROPOMI
L2__FRESCO (KNMI) Cloud fraction and cloud pressure with a spatial resolution of 5.5 × 3.5 km2 observed
at about 13:30 local solar time from spectra measured by TROPOMI (KNMI FRESCO cloud support
product)
L2__O22CLD (KNMI) O2 –O2 cloud retrieval with a spatial resolution of 5.5 × 3.5 km2 observed at about
13:30 local solar time from spectra measured by TROPOMI (KNMI O2 –O2 cloud support product)
gmd:credit‘%(credit)s’ (static)

NC_STRING

Recognition of those who contributed to the resource(s).
gmd:language‘eng’ (static)

NC_STRING

gmd:topicCategory‘climatologyMeteorologyAtmosphere’ (static)

NC_STRING‘gmd:MD_DataIdentification’ (static)

NC_STRING

Main theme(s) of the dataset.
objectType

Name of the metadata class [RD33, table 10].
10.2.3.10

Group “gmd:citation” in “gmd:identificationInfo”

Citation data for the resource.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:citation
Group attributes attached to gmd:citation
Name

Value

gmd:title

Type
NC_STRING

Name by which the cited resource is known. This is the same as the global “title” attribute.
objectType‘gmd:CI_Citation’ (static)

NC_STRING

Name of the metadata class [RD33, table 11].
10.2.3.11

Group “gmd:date” in “gmd:citation”

Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:citation/gmd:date

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Group attributes attached to gmd:date
Name

Value

Type

gmd:date‘%(processor_release_date)s’ (static)

NC_STRING

objectType‘gmd:CI_Date’ (static)

NC_STRING

10.2.3.12

Group “gmd:dateType” in “gmd:date”

Event used for reference date.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:citation/gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘creation’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.13

Group “gmd:identifier” in “gmd:citation”

Unique identifier for metadata file, see the Level 1B metadata specification [RD33, table 5] for a discussion of
the value.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:citation/gmd:identifierGroup attributes attached to gmd:identifier
Name

Value

Type

gmd:code‘urn:ogc:def:EOP:ESA:SENTINEL.S5P_TROP_%(shortname)s’ (dynamic)

NC_STRING

Replace “%(shortname)s” with the “ProductShortName” value from the Level 2 “/METADATA/GRANULE_DESCRIPTION” metadata group.
objectType
10.2.3.14‘gmd:MD_Identifier’ (static)

NC_STRING

Group “gmd:pointOfContact” in “gmd:identificationInfo”

See description of the “gmd:contact” attribute above.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:pointOfContact
Group attributes attached to gmd:pointOfContact
Name

Value

Type

gmd:organisationName‘Copernicus Space Component Data Access System,
ESA, Services Coordinated Interface’ (static)

NC_STRING

objectType‘gmd:CI_ResponsibleParty’ (static)

NC_STRING

10.2.3.15

Group “gmd:contactInfo” in “gmd:pointOfContact”

Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:pointOfContact/gmd:contactInfo
Group attributes attached to gmd:contactInfo
Name

Value

Type

objectType‘gmd:CI_Contact’ (static)

NC_STRING

10.2.3.16

Group “gmd:address” in “gmd:contactInfo”

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Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:pointOfContact/gmd:contactInfo/
gmd:addressGroup attributes attached to gmd:address
Name

Value

Type

gmd:electronicMailAddress‘EOSupport@copernicus.esa.int’ (static)

NC_STRING

objectType‘gmd:CI_Address’ (static)

NC_STRING

10.2.3.17

Group “gmd:role” in “gmd:pointOfContact”

Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:pointOfContact/gmd:role
Group attributes attached to gmd:role
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_RoleCode’ (static)

NC_STRING

codeListValue‘distributor’ (static)

NC_STRING

objectType‘gmd:CI_RoleCode’ (static)

NC_STRING

10.2.3.18

Group “gmd:descriptiveKeywords#1” in “gmd:identificationInfo”

Provides category keywords, their type, and reference source. Within the framework of GEMET the choise of
keywords is very limited. More meaningful keywords can be derived from the Climate and Forecast metadadaconventions’ standard name list, see “gmd:descriptiveKeywords#2” below.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:descriptiveKeywords#1
Group attributes attached to gmd:descriptiveKeywords#1
Name

Value

Type

gmd:keyword#1‘Atmospheric conditions’ (static)

NC_STRING

objectType‘gmd:MD_Keywords’ (static)

NC_STRING

10.2.3.19

Group “gmd:type” in “gmd:descriptiveKeywords#1”

Subject matter used to group similar keywords.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:descriptiveKeywords#1/
gmd:type
Group attributes attached to gmd:type
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#MD_KeywordTypeCode’ (static)

NC_STRING

codeListValue‘theme’ (static)

NC_STRING

objectType‘gmd:MD_KeywordTypeCode’ (static)

NC_STRING

10.2.3.20

Group “gmd:thesaurusName” in “gmd:descriptiveKeywords#1”

Name by which the cited resource is known.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:descriptiveKeywords#1/
gmd:thesaurusName

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Group attributes attached to gmd:thesaurusName
Name

Value

Type

gmd:title‘GEMET - INSPIRE themes, version 1.0’ (static)

NC_STRING

objectType‘gmd:CI_Citation’ (static)

NC_STRING

10.2.3.21

Group “gmd:date” in “gmd:thesaurusName”

Reference date for the cited resource.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:descriptiveKeywords#1/
gmd:thesaurusName/gmd:dateGroup attributes attached to gmd:date
Name

Value

Type

gmd:date‘2008-06-01’ (static)

NC_STRING

objectType‘gmd:CI_Date’ (static)

NC_STRING

10.2.3.22

Group “gmd:dateType” in “gmd:date”

What date is used for the reference date.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:descriptiveKeywords#1/
gmd:thesaurusName/gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘publication’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.23

Group “gmd:descriptiveKeywords#2” in “gmd:identificationInfo”

Provides category keywords, their type, and reference source. These keywords are taken from the Climate
and Forecast metadada conventions’ standard name list [ER5]. The keywords listed below identify the mostimportant parameters in the product.
L2__AER_AI (KNMI) ultraviolet_aerosol_index
L2__AER_LH (KNMI) height_of_elevated_aerosol_layer
L2__NO2___ (KNMI) troposphere_mole_content_of_nitrogen_dioxide, stratosphere_mole_content_of_nitrogen_dioxide, atmosphere_mole_content_of_nitrogen_dioxide
L2__O3__PR (KNMI) mole_fraction_of_ozone_in_air
L2__CH4___ (SRON) atmosphere_mole_fraction_of_methane_in_dry_air
L2__CO____ (SRON) atmosphere_mole_content_of_carbon_monoxide
L2__FRESCO (KNMI) air_pressure_at_cloud_optical_centroid, effective_cloud_area_fraction_assuming_fixed_cloud_albedo, cloud_albedo_assuming_completely_cloudy_sky, air_pressure_at_cloud_optical_centroid_assuming_completely_cloudy_sky
L2__O22CLD (KNMI) air_pressure_at_cloud_optical_centroid, effective_cloud_area_fraction_assuming_fixed_cloud_albedo, cloud_albedo_assuming_completely_cloudy_sky, air_pressure_at_cloud_optical_centroid_assuming_completely_cloudy_sky
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:descriptiveKeywords#2

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Group attributes attached to gmd:descriptiveKeywords#2
Name

Value

Type

gmd:keyword#1
objectType
10.2.3.24

NC_STRING‘gmd:MD_Keywords’ (static)

NC_STRING

Group “gmd:thesaurusName” in “gmd:descriptiveKeywords#2”

Name by which the cited resource is known.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:descriptiveKeywords#2/
gmd:thesaurusName
Group attributes attached to gmd:thesaurusName
Name

Value

Type

gmd:title‘CF Standard Name Table v65’ (static)

NC_STRING

xlink:href‘http://cfconventions.org/standard-names.html’namic)

objectType‘gmd:CI_Citation’ (static)

10.2.3.25(dy-

NC_STRING
NC_STRING

Group “gmd:date” in “gmd:thesaurusName”

Reference date for the cited resource.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:descriptiveKeywords#2/
gmd:thesaurusName/gmd:dateGroup attributes attached to gmd:date
Name

Value

Type

gmd:date‘2019-04-09’ (static)

NC_STRING

objectType‘gmd:CI_Date’ (static)

NC_STRING

10.2.3.26

Group “gmd:dateType” in “gmd:date”

What date is used for the reference date.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:descriptiveKeywords#2/
gmd:thesaurusName/gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘publication’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.27

Group “gmd:resourceConstraints” in “gmd:identificationInfo”

Provides information about constraints which apply to the resource.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:resourceConstraints
Group attributes attached to gmd:resourceConstraints
Name

Value

Type

gmd:useLimitation‘no conditions apply’ (static)

NC_STRING

Limitation affecting the fitness for use of the resource or metadata.
objectType‘gmd:MD_LegalConstraints’ (static)

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Group “gmd:accessConstraints” in “gmd:resourceConstraints”

Access constraints applied to assure the protection of privacy or intellectual property, and any special restrictions
or limitations on obtaining the resource or metadata.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:resourceConstraints/
gmd:accessConstraints
Group attributes attached to gmd:accessConstraints
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#MD_RestrictionCode’ (static)

NC_STRING

codeListValue‘copyright’ (static)

NC_STRING

objectType‘gmd:MD_RestrictionCode’ (static)

NC_STRING

10.2.3.29

Group “gmd:spatialRepresentationType” in “gmd:identificationInfo”

Method used to spatially represent geographic information.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:spatialRepresentationType
Group attributes attached to gmd:spatialRepresentationType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#MD_SpatialRepresentationTypeCode’ (static)

NC_STRING

codeListValue‘grid’ (static)

NC_STRING

objectType‘gmd:MD_SpatialRepresentationTypeCode’ (static)

NC_STRING

10.2.3.30

Group “gmd:characterSet” in “gmd:identificationInfo”

Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:characterSet
Group attributes attached to gmd:characterSet
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#MD_CharacterSetCode’ (static)

NC_STRING

codeListValue‘utf8’ (static)

NC_STRING

objectType‘gmd:MD_CharacterSetCode’ (static)

NC_STRING

10.2.3.31

Group “gmd:extent” in “gmd:identificationInfo”

Extent information including the bounding box, bounding polygon, vertical, and temporal extent of the dataset.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:extent
Group attributes attached to gmd:extent
Name

Value

Type

objectType‘gmd:EX_Extent’ (static)

NC_STRING

10.2.3.32

Group “gmd:geographicElement” in “gmd:extent”

Geographic position of the granule. This is only an approximate reference so specifying the coordinate
reference system is unnecessary. The usual limitations apply: −180◦ ≤ ϑ ≤ 180◦ and −90◦ ≤ δ ≤ 90◦ . Notethat for full orbits these values provide little information as at lease one pole will be present in the data, ensuring
full longitudinal coverage.

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Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:extent/gmd:geographicElement
Group attributes attached to gmd:geographicElement
Name

Value

Type

gmd:eastBoundLongitude180.0 (dynamic)

NC_FLOAT

gmd:northBoundLatitude

90.0 (dynamic)

NC_FLOAT

gmd:southBoundLatitude-90.0 (dynamic)

NC_FLOAT

gmd:westBoundLongitude-180.0 (dynamic)

NC_FLOAT

gmd:extentTypeCode‘true’ (static)

NC_STRING

Indication of whether the bounding polygon encompasses an area covered by the data or an area wheredata is not present. The value “true” indicates inclusion.
objectType
10.2.3.33‘gmd:EX_GeographicBoundingBox’ (static)

NC_STRING

Group “gmd:temporalElement” in “gmd:extent”

Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:extent/gmd:temporalElement
Group attributes attached to gmd:temporalElement
Name

Value

Type

objectType‘gmd:EX_TemporalExtent’ (static)

NC_STRING

10.2.3.34

Group “gmd:extent” in “gmd:temporalElement”

Time period covered by the content of the dataset.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:extent/gmd:temporalElement/
gmd:extent
Group attributes attached to gmd:extent
Name

Value

Type

gml:beginPosition‘2014-11-14T19:58:00’ (dynamic)

NC_STRING

Time of the start of the granule, expressed as ISO 8601 [RD34] date-time string.
gml:endPosition‘2014-11-14T20:08:00’ (dynamic)

NC_STRING

Time of the end of the granule, expressed as ISO 8601 [RD34] date-time string.
objectType
10.2.3.35‘gml:TimePeriod’ (static)

NC_STRING

Group “gmd:dataQualityInfo” in “ISO_METADATA”

This group contains a general assessment of the quality of the dataset. In addition, the package contains
information about the sources and production processes used in producing a dataset, which is of particularimportance for imagery and gridded data.
For the TROPOMI level 2 products the use of the contained class LI_Lineage (group “gmd:lineage”,
section 10.2.3.43 on page 84) is important for describing the sources which are either used or produced(output) in a series of process steps. The sources refer to the various L1b data products used as inputs (andthe L0 products used in producing those products) and the auxiliary data (static and especially dynamic) when
producing the L2 products.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo
Group attributes attached to gmd:dataQualityInfo
Name

Value

Type

objectType‘gmd:DQ_DataQuality’ (static)

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Group “gmd:scope” in “gmd:dataQualityInfo”

The specific data to which the data quality information applies.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:scopeGroup attributes attached to gmd:scope
Name

Value

Type

objectType‘gmd:DQ_Scope’ (static)

NC_STRING

10.2.3.37

Group “gmd:level” in “gmd:scope”

Hierarchical level of the data specified by the scope.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:scope/gmd:level
Group attributes attached to gmd:level
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#MD_ScopeCode’ (static)

NC_STRING

codeListValue‘dataset’ (static)

NC_STRING

objectType‘gmd:MD_ScopeCode’ (static)

NC_STRING

10.2.3.38

Group “gmd:report” in “gmd:dataQualityInfo”

Value (or set of values) obtained from applying a data quality measure or the outcome of evaluating theobtained value (or set of values) against a specified acceptable conformance quality level.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:report
Group attributes attached to gmd:report
Name

Value

Type

objectType‘gmd:DQ_DomainConsistency’ (static)

NC_STRING

10.2.3.39

Group “gmd:result” in “gmd:report”

Value (or set of values) obtained from applying a data quality measure or the outcome of evaluating theobtained value (or set of values) against a specified acceptable conformance quality level.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:report/gmd:result
Group attributes attached to gmd:result
Name

Value

Type

objectType‘gmd:DQ_ConformanceResult’ (static)

NC_STRING

gmd:pass‘true’ (static)

NC_STRING

Indication of confomance result. The value “true” indicates “pass”.
gmd:explanation‘INSPIRE Data specification for orthoimagery is not
yet officially published so conformity has not yet been
evaluated’ (static)

NC_STRING

Explanation of the meaning of conformance for this result. Within the context of INSPIRE conformance cancurrently not be determined.
10.2.3.40

Group “gmd:specification” in “gmd:result”

Citation of product specification or user requirement against which data is being evaluated.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:report/gmd:result/gmd:specification

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Group attributes attached to gmd:specification
Name

Value

Type

objectType‘gmd:CI_Citation’ (static)

NC_STRING

gmd:title‘INSPIRE Data Specification on Orthoimagery Guidelines, version 3.0rc3’ (static)

NC_STRING

10.2.3.41

Group “gmd:date” in “gmd:specification”

Reference date for the cited resource.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:report/gmd:result/gmd:specification/
gmd:date
Group attributes attached to gmd:date
Name

Value

Type

gmd:date‘2013-02-04’ (static)

NC_STRING

objectType‘gmd:CI_Date’ (static)

NC_STRING

10.2.3.42

Group “gmd:dateType” in “gmd:date”

Meaning of the reference date for the cited resource.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:report/gmd:result/gmd:specification/
gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘publication’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.43

Group “gmd:lineage” in “gmd:dataQualityInfo”

Non-quantitative quality information about the lineage of the data specified by the scope.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage
Group attributes attached to gmd:lineage
Name

Value

Type

objectType‘gmd:LI_Lineage’ (static)

NC_STRING

gmd:statement‘L2 %(product)s dataset produced by %(processingcenter)s from the S5P/TROPOMI L1B product’ (dynamic)

NC_STRING

General explanation of the data producer’s knowledge about the lineage of a dataset. Insert short descriptionof the actual Level 2 product in this string (at the %(. . . )s).
10.2.3.44

Group “gmd:processStep” in “gmd:lineage”

Information about an event or transformation in the life of the dataset including details of the algorithm andsoftware used for processing.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep
Group attributes attached to gmd:processStep
Name

Value

Type

objectType‘gmi:LE_ProcessStep’ (static)

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NC_STRING

Description of the event, including related parameters or tolerances. Insert short description of the actual
Level 2 product, the orbit number, the name of the institude responsible for the CFI and the software version
in this string (at the respective %(. . . )s and %(. . . )d).
10.2.3.45

Group “gmi:output” in “gmd:processStep”

Description of the output.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:output
Group attributes attached to gmi:output
Name

Value

gmd:description

Type
NC_STRING

Short description of the output, a copy of the global ‘title’ attribute.
objectType
10.2.3.46‘gmi:LE_Source’ (static)

NC_STRING

Group “gmd:sourceCitation” in “gmi:output”

Reference to the actual filename of the output data and production date and time.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:output/gmd:sourceCitation
Group attributes attached to gmd:sourceCitation
Name

Value

Type

gmd:title‘%(logical_filename)s’ (dynamic)

NC_STRING

Output file name without extension.
objectType
10.2.3.47‘gmd:CI_Citation’ (static)

NC_STRING

Group “gmd:date” in “gmd:sourceCitation”

Production date and time of the output file.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:output/gmd:sourceCitation/gmd:dateGroup attributes attached to gmd:date
Name

Value

gmd:date

Type
NC_STRING

Production date and time of the output file. Note that the definition in the XML schema appears to allow theuse of a “CI_DateTime” instead of a “CI_Date”.
objectType
10.2.3.48‘gmd:CI_DateTime’ (static)

NC_STRING

Group “gmd:dateType” in “gmd:date”

Meaning of the reference date for the cited resource.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:output/gmd:sourceCitation/gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

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codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘creation’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.49

Group “gmd:identifier” in “gmd:sourceCitation”

Identification of the output product.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:output/gmd:sourceCitation/gmd:identifierGroup attributes attached to gmd:identifier
Name

Value

Type

gmd:code‘%(shortname)s’ (dynamic)

NC_STRING

The product short name, a copy of the ‘ProductShortName’ attribute in ‘/METADATA/GRANULE_DESCRIPTION’.
objectType
10.2.3.50‘gmd:MD_Identifier’ (static)

NC_STRING

Group “gmi:processedLevel” in “gmi:output”

Process level of the output file.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:output/gmi:processedLevel
Group attributes attached to gmi:processedLevel
Name

Value

gmd:code‘L2’ (static)

NC_STRING

objectType‘gmd:MD_Identifier’ (static)

NC_STRING

10.2.3.51

TypeGroup “gmi:processingInformation” in “gmd:processStep”

Description of the processor in more detail.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:processingInformation
Group attributes attached to gmi:processingInformation
Name

Value

Type

objectType‘gmi:LE_Processing’ (static)

NC_STRING

10.2.3.52

Group “gmi:identifier” in “gmi:processingInformation”

Identification of the processor.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:processingInformation/gmi:identifierGroup attributes attached to gmi:identifier
Name

Value

Type

gmd:code‘%(institute)s L2 %(product)s processor, version %(version)s’ (dynamic)

NC_STRING

Descriptive name of the processor, with the %(. . . )s placeholders replaced with the responsible institute’s
name, product name and software release version.
objectType‘gmd:MD_Identifier’ (static)

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Group “gmi:softwareReference” in “gmi:processingInformation”

Reference to document describing processing software.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:processingInformation/gmi:softwareReferenceGroup attributes attached to gmi:softwareReference
Name

Value

Type

gmd:title‘%(processor_name)s processor’ (dynamic)

NC_STRING‘gmd:CI_Citation’ (static)

NC_STRING

Name of the processor.
objectType
10.2.3.54

Group “gmd:date” in “gmi:softwareReference”

Release date (compile date) of the processor.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:processingInformation/gmi:softwareReference/gmd:dateGroup attributes attached to gmd:date
Name

Value

Type

gmd:date‘%(processor_release_date)s’ (dynamic)

NC_STRING

Release date of the processor expressed as an ISO 8601 date string [RD34].
objectType
10.2.3.55‘gmd:CI_DateTime’ (static)

NC_STRING

Group “gmd:dateType” in “gmd:date”

The release date of the processor.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:processingInformation/gmi:softwareReference/gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘creation’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.56

Group “gmi:documentation#1” in “gmi:processingInformation”

Reference to the ATBD of the product.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:processingInformation/gmi:documentation#1
Group attributes attached to gmi:documentation#1
Name

Value

Type

objectType‘gmd:CI_Citation’ (static)

NC_STRING

gmd:title‘%(title_atbd)s’ (dynamic)

NC_STRING

Specification of the current release of the ATBD of the product.
doi‘%(atbd_doi)s’ (dynamic)

DOI for the algorithm theoretical basis document.
10.2.3.57

Group “gmd:date” in “gmi:documentation#1”

Release date of the ATBD.

NC_STRINGS5P L2 PUM UV Aerosol Index
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Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:processingInformation/gmi:documentation#1/gmd:dateGroup attributes attached to gmd:date
Name

Value

Type

gmd:date‘%(date_atbd)s’ (dynamic)

NC_STRING

Release date of the ATBD expressed as an ISO 8601 date string [RD34].
objectType
10.2.3.58‘gmd:CI_Date’ (static)

NC_STRING

Group “gmd:dateType” in “gmd:date”

Specify the type of the date of the ATBD (revision of publication).
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:processingInformation/gmi:documentation#1/gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘revision’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.59

Group “gmi:documentation#2” in “gmi:processingInformation”

Reference to the PUM of the product.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:processingInformation/gmi:documentation#2
Group attributes attached to gmi:documentation#2
Name

Value

Type

objectType‘gmd:CI_Citation’ (static)

NC_STRING

gmd:title‘%(title_pum)s’ (dynamic)

NC_STRING

Specification of the current release of the PUM of the product.
doi‘%(pum_doi)s’ (dynamic)

NC_STRING

DOI for the product user manual.
10.2.3.60

Group “gmd:date” in “gmi:documentation#2”

Release date of the PUM.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:processingInformation/gmi:documentation#2/gmd:dateGroup attributes attached to gmd:date
Name

Value

Type

gmd:date‘%(date_pum)s’ (dynamic)

NC_STRING

Release date of the PUM expressed as an ISO 8601 date string [RD34].
objectType
10.2.3.61‘gmd:CI_Date’ (static)

NC_STRING

Group “gmd:dateType” in “gmd:date”

Specify the type of the date of the PUM (revision of publication).
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:processingInformation/gmi:documentation#2/gmd:date/gmd:dateType

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Group attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘revision’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.62

Group “gmi:report” in “gmd:processStep”

Short report of what occurred during the process step.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmi:report
Group attributes attached to gmi:report
Name

Value

Type

gmi:description‘Sentinel 5-precursor TROPOMI L1b processed to L2
data using the %(institute)s L2 %(product)s processor’(dynamic)

NC_STRING

Textual description of what occurred during the process step. Replace %(. . . )s as indicated.
gmi:fileType‘netCDF-4’ (static)

NC_STRING

Type of file that contains the processing report, in our case the processing report is contained in the main
output file.
gmi:name‘%(logical_filename)s.nc’ (dynamic)

NC_STRING

objectType‘gmi:LE_ProcessStepReport’ (dynamic)

NC_STRING

10.2.3.63

Group “gmd:source#1” in “gmd:processStep”

Information about the source data used in creating the data specified by the scope. Repeat group as needed,
incrementing the number of the source (after the # mark).
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmd:source#1
Group attributes attached to gmd:source#1
Name

Value

objectType‘gmi:LE_Source’ (static)

gmd:description

Type
NC_STRING
NC_STRING

Description of the input data, including L1B, L2, dynamic auxiliary input data and semi-static auxiliary
input data. Base strings are “TROPOMI L1B %s radiance product”, “TROPOMI L1B %s irradianceproduct”, “TROPOMI L2 %s product”, “Auxiliary ECMWF %s Meteorological forecast data”, “Processor %s
configuration file”, “Auxiliary %s reference data”, “Auxiliary %s algorithm lookup table”, “Auxiliary CTM %s
model input data”, “Auxiliary snow and ice input data” and “Auxiliary NPP/VIIRS cloud screening input data”.
The %s to be replaced with specific descriptors.
10.2.3.64

Group “gmi:processedLevel” in “gmd:source#1”

Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmd:source#1/gmi:processedLevel
Group attributes attached to gmi:processedLevel
Name

Value

Type

gmd:code

Empty!

NC_STRING

objectType‘gmd:MD_Identifier’ (static)

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Group “gmd:sourceCitation” in “gmd:source#1”

Reference to the actual filename of the input data.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmd:source#1/gmd:sourceCitation
Group attributes attached to gmd:sourceCitation
Name

Value

Type

objectType‘gmd:CI_Citation’ (static)

NC_STRING

10.2.3.66

Group “gmd:date” in “gmd:sourceCitation”

Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmd:source#1/gmd:sourceCitation/gmd:dateGroup attributes attached to gmd:date
Name

Value

gmd:date

Type
NC_STRING

Production date and time of the input file(s) in this group expressed as an ISO 8601 date-time string [RD34].
Note that the definition in the XML schema appears to allow the use of a “CI_DateTime” instead of a
“CI_Date”.
objectType
10.2.3.67‘gmd:CI_Date’ (static)

NC_STRING

Group “gmd:dateType” in “gmd:date”

Meaning of the reference date for the cited resource.
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmd:source#1/gmd:sourceCitation/gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘creation’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.68

Group “gmd:title” in “gmd:sourceCitation”

Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/
gmd:source#1/gmd:sourceCitation/gmd:title
Group attributes attached to gmd:title
Name

Value

gco:characterStringType
NC_STRING

Textual description of the input file group (same as the “gmd:description” attribute in the “gmi:LE_Source” object).
10.2.3.69

Group “gmd:alternateTitle#1” in “gmd:sourceCitation”

All filenames in this group, in case more files of a particular file type are delivered, for instance for meteorologicalor model input. Repeat group as needed, incrementing the number of the input file (after the # mark).
Attributes in AER_AI/METADATA/ISO_METADATA/gmd:dataQualityInfo/gmd:lineage/gmd:processStep/

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gmd:source#1/gmd:sourceCitation/gmd:alternateTitle#1
Group attributes attached to gmd:alternateTitle#1
Name

Value

Type

gmx:FileName

Empty!

NC_STRING

The basename of the input file.
10.2.3.70

Group “gmi:acquisitionInformation” in “ISO_METADATA”

Metadata regarding the acquisition of the original data.
Attributes in AER_AI/METADATA/ISO_METADATA/gmi:acquisitionInformation
Group attributes attached to gmi:acquisitionInformation
Name

Value

Type

objectType‘gmi:MI_AcquisitionInformation’ (static)

NC_STRING

10.2.3.71

Group “gmi:platform” in “gmi:acquisitionInformation”

The platform we are on.
Attributes in AER_AI/METADATA/ISO_METADATA/gmi:acquisitionInformation/gmi:platform
Group attributes attached to gmi:platform
Name

Value

gmi:description‘Sentinel 5 Precursor’ (static)

NC_STRING

objectType‘gmi:MI_Platform’ (static)

NC_STRING

10.2.3.72

TypeGroup “gmi:identifier” in “gmi:platform”

Short identifier of the platform.
Attributes in AER_AI/METADATA/ISO_METADATA/gmi:acquisitionInformation/gmi:platform/gmi:identifierGroup attributes attached to gmi:identifier
Name

Value

Type

gmd:code‘S5P’ (static)

NC_STRING

gmd:codeSpace‘http://www.esa.int/’ (static)

NC_STRING

objectType‘gmd:RS_Identifier’ (static)

NC_STRING

10.2.3.73

Group “gmi:instrument” in “gmi:platform”

The instrument used for the observations.
Attributes in AER_AI/METADATA/ISO_METADATA/gmi:acquisitionInformation/gmi:platform/gmi:instrument
Group attributes attached to gmi:instrument
Name

Value

Type

objectType‘gmi:MI_Instrument’ (static)

NC_STRING

gmi:type‘UV-VIS-NIR-SWIR imaging spectrometer’ (static)

NC_STRING

Type of the instrument.
10.2.3.74

Group “gmi:identifier” in “gmi:instrument”

Unique identifier for the instrument.
Attributes in AER_AI/METADATA/ISO_METADATA/gmi:acquisitionInformation/gmi:platform/gmi:instrument/
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Group attributes attached to gmi:identifier
Name

Value

Type

gmd:code‘TROPOMI’ (static)

NC_STRING‘http://www.esa.int/’ (static)

NC_STRING

The actual identifier.
gmd:codeSpace

Name or identifier of the organization responsible for the namespace.
objectType
10.2.3.75‘gmd:RS_Identifier’ (static)

NC_STRING

Group “EOP_METADATA” in “EOP_metadata”

Based on the OGC 10-025 standard for Observations & Measurements [RD38], an Earth Observation Product(EOP) schema was developed which refines an observation into the feature type earth observation. This
schema was then extended with sensor-specific thematic schemas.
Attributes in AER_AI/METADATA/EOP_METADATAGroup attributes attached to EOP_METADATA
Name

Value

Type

gml:id‘%(logical_filename)s.ID’ (dynamic)

NC_STRING

Unique ID for this “atm:EarthObservation” object. Constructed from the logical output filename and theextension “ID” separated by a dot.
objectType
10.2.3.76‘atm:EarthObservation’ (static)

NC_STRING

Group “om:phenomenonTime” in “EOP_METADATA”

Time coverage of the granule.
Attributes in AER_AI/METADATA/EOP_METADATA/om:phenomenonTime
Group attributes attached to om:phenomenonTime
Name

Value

gml:beginPosition

Type
NC_STRING

Start of time coverage of the data in the granule expressed as an ISO 8601 date-time string [RD34].
gml:endPosition

NC_STRING

End of time coverage of the data in the granule expressed as an ISO 8601 date-time string [RD34].
objectType
10.2.3.77‘gml:TimePeriod’ (static)

NC_STRING

Group “om:procedure” in “EOP_METADATA”

Platform, instrument and sensor used for the acquisition and the acquisition parameters.
Attributes in AER_AI/METADATA/EOP_METADATA/om:procedure
Group attributes attached to om:procedure
Name

Value

Type

gml:id‘%(logical_filename)s.EOE’ (dynamic)

NC_STRING

Unique ID for this “eop:EarthObservationEquipment” object. Constructed from the logical output filename
and the extension “EOE” separated by a dot.
objectType
10.2.3.78‘eop:EarthObservationEquipment’ (static)Group “eop:platform” in “om:procedure”

Platform name and orbit type.
Attributes in AER_AI/METADATA/EOP_METADATA/om:procedure/eop:platform

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Group attributes attached to eop:platform
Name

Value

Type

eop:shortName‘Sentinel-5p’ (static)

NC_STRING

objectType‘eop:Platform’ (static)

NC_STRING

10.2.3.79

Group “eop:instrument” in “om:procedure”

Instrument descriptor.
Attributes in AER_AI/METADATA/EOP_METADATA/om:procedure/eop:instrument
Group attributes attached to eop:instrument
Name

Value

Type

eop:shortName‘TROPOMI’ (static)

NC_STRING

objectType‘eop:Instrument’ (static)

NC_STRING

10.2.3.80

Group “eop:sensor” in “om:procedure”

Sensor description.
Attributes in AER_AI/METADATA/EOP_METADATA/om:procedure/eop:sensor
Group attributes attached to eop:sensor
Name

Value

Type

eop:sensorType‘ATMOSPHERIC’ (static)

NC_STRING

objectType‘eop:Sensor’ (static)

NC_STRING

10.2.3.81

Group “eop:acquisitionParameters” in “om:procedure”

Additional parameters describing the data acquisition. Only an orbit number is used here.
Attributes in AER_AI/METADATA/EOP_METADATA/om:procedure/eop:acquisitionParameters
Group attributes attached to eop:acquisitionParameters
Name

Value

Type

eop:orbitNumber

0 (dynamic)

NC_INT

objectType‘eop:Acquisition’ (static)

NC_STRING

10.2.3.82

Group “om:observedProperty” in “EOP_METADATA”

An xlink to the observed property definition.
Attributes in AER_AI/METADATA/EOP_METADATA/om:observedProperty
Group attributes attached to om:observedProperty
Name

Value

Type

nilReason‘inapplicable’ (dynamic)

NC_STRING

This element should use the attribute ‘nilReason=”inapplicable”’.
10.2.3.83

Group “om:featureOfInterest” in “EOP_METADATA”

Attributes in AER_AI/METADATA/EOP_METADATA/om:featureOfInterest
Group attributes attached to om:featureOfInterest
Name

Value

Type

objectType‘eop:FootPrint’ (static)

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NC_STRING

Unique ID for this “eop:FootPrint” object. Constructed from the logical output filename and the extension“FP” separated by a dot.
10.2.3.84

Group “eop:multiExtentOf” in “om:featureOfInterest”

Acquisition footprint coordinates, described by a closed polygon – the last point is equal to the first point, using
latitude, longitude pairs. The expected structure is “gml:Polygon/gml:exterior/gml:LinearRing/gml:posList”.
Attributes in AER_AI/METADATA/EOP_METADATA/om:featureOfInterest/eop:multiExtentOf
Group attributes attached to eop:multiExtentOf
Name

Value

Type

objectType‘gml:MultiSurface’ (static)

NC_STRING

10.2.3.85

Group “gml:surfaceMembers” in “eop:multiExtentOf”

Attributes in AER_AI/METADATA/EOP_METADATA/om:featureOfInterest/eop:multiExtentOf/gml:surfaceMembers
Group attributes attached to gml:surfaceMembers
Name

Value

Type

objectType‘gml:Polygon’ (static)

NC_STRING

10.2.3.86

Group “gml:exterior” in “gml:surfaceMembers”

Attributes in AER_AI/METADATA/EOP_METADATA/om:featureOfInterest/eop:multiExtentOf/gml:surfaceMembers/
gml:exteriorGroup attributes attached to gml:exterior
Name

Value

gml:posList

Type
NC_STRING

The Polygon geometry shall be encoded in the EPSG:4326 geographic coordinate reference system(WGS-84) and the coordinate pairs shall be ordered as latitude/longitude. Polygons enclose areas withpoints listed in counter-clockwise direction.
objectType
10.2.3.87‘gml:LinearRing’ (static)

NC_STRING

Group “eop:metaDataProperty” in “EOP_METADATA”

This group contains all the metadata relative to the Eath observation product that do not fit inside one of theother groups, i.e. metadata that do not describe the time, the mechanism, the location or the result of theobservation.
These metadata are mainly the EarthObservation identifier, the acquisition type and information relative tothe downlink and archiving centers.
Attributes in AER_AI/METADATA/EOP_METADATA/eop:metaDataProperty
Group attributes attached to eop:metaDataProperty
Name

Value

Type

objectType‘eop:EarthObservationMetaData’ (static)

NC_STRING

eop:acquisitionType‘NOMINAL’ (dynamic)

NC_STRING

Used to distinguish at a high level the appropriateness of the acquisition for “general” use, whether the
product is a nominal acquisition, special calibration product or other. Copy from L1b. For Level 2 this should
always be ‘NOMINAL’.

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NC_STRING‘%(product_doi)s’ (dynamic)

NC_STRING

Logical file name.
eop:doi

Digital Object Identifier identifying the product (see http://www.datacite.org for DOIs for datasets).
eop:parentIdentifier‘urn:ogc:def:EOP:ESA:SENTINEL.S5P_TROP_%(shortname)s’ (dynamic)

NC_STRING

Unique collection identifier for metadata file, see the Level 1B metadata specification [RD33, table 5] for a
discussion of the value.
This is a copy of the “gmd:fileIdentifier” attribute in the “/METADATA/ISO_METADATA” group.
eop:productType‘S5P_%(mode)s_%(product)s’ (dynamic)

NC_STRING

Product type identifier. Replace %(mode)s with the operational mode the processor is running in (‘NRTI’,‘OFFL’ or ‘RPRO’, as per [RD25]) and %(product)s with the 10 character output file name semantic
descriptors as given in [RD39, RD40, RD41].
eop:status‘ACQUIRED’ (dynamic)

NC_STRING

Refers to product status. Values listed in the standard: ‘ARCHIVED’, ‘ACQUIRED’, ‘CANCELLED’, ‘FAILED’,‘PLANNED’, ‘POTENTIAL’, ‘REJECTED’, ‘QUALITY-DEGRADED’. Copied from L1B.
eop:productQualityStatus‘NOMINAL’ (dynamic)

NC_STRING

Indicator that specifies whether the product quality is degraded or not. Allowed values: ‘DEGRADED’,‘NOMINAL’.
eop:productQualityDegradationTag‘NOT APPLICABLE’ (dynamic)

NC_STRING

Contains further textual information concerning the quality degradation. According to the metadata standards
it shall be provided only if “eop:productQualityStatus” value is set to ‘DEGRADED’. Because the way wegenerate out output files, this attribute will always be present, even when “eop:productQualityStatus” valueis ‘NOMINAL’. In those cases the value shall be set to “NOT APPLICABLE”.
Possible values are “MISSING AUXILIARY INPUT” and “NOT APPLICABLE”. Note that Level 1B does not
set this value, so only problems detectable in the processor are covered.
10.2.3.88

Group “eop:processing” in “eop:metaDataProperty”

Processing information.
Attributes in AER_AI/METADATA/EOP_METADATA/eop:metaDataProperty/eop:processing
Group attributes attached to eop:processing
Name

Value

Type

objectType‘eop:ProcessingInformation’ (static)

NC_STRING

eop:processingCenter‘%(processingcenter)s’ (dynamic)

NC_STRING

The processing center, taken from the “Processing_Station” key in the joborder.
eop:processingDate‘YYYY-mm-ddTHH:MM:SSZ’ (dynamic)

NC_STRING

The processing date, as an ISO 8601 date-time string [RD34].
eop:processingLevel‘L2’ (static)

NC_STRING‘%(processor_name)s’ (static)

NC_STRING

These are all Level 2 products.
eop:processorName

The name of the processor, “tropnll2dp.exe” for KNMI and “upas-l2” for DLR.
eop:processorVersion‘%(version)s’ (dynamic)

NC_STRING

Version of the processor, as “major.minor.bugfix”.
eop:nativeProductFormat‘netCDF-4’ (static)

NC_STRING‘%(mode)s’ (dynamic)

NC_STRING

Native product format.
eop:processingMode

Processing mode taken from mission specific code list. For S5P we use the File Class identifiers [RD25,
section 4.1.2]: ‘TEST’, ‘OGCA’, ‘GSOV’, ‘OPER’, ‘NRTI’, ‘OFFL’, ‘RPRO’.

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Group “ESA_METADATA” in “ESA_metadata”

Metadata defined in the ESA file format standard [RD27].
10.2.3.90

Group “earth_explorer_header” in “ESA_METADATA”

Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header
Group attributes attached to earth_explorer_header
Name

Value

Type

objectType‘Earth_Explorer_Header’ (static)

NC_STRING

10.2.3.91

Group “fixed_header” in “earth_explorer_header”

The fixed header. We do not use a variable header, so only the fixed header is present.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/fixed_header
Group attributes attached to fixed_header
Name

Value

Type

objectType‘Fixed_Header’ (static)

NC_STRING

File_Name‘%(logical_filename)s’ (dynamic)

NC_STRING

The logical file name, i.e. the file name without extension.
File_Description

NC_STRING

This is a copy of the global “title” attribute.
Notes

NC_STRING

This is a copy of the global “comment” attribute.
Mission‘S5P’ (static)

NC_STRING

The mission identifier for the Sentinel 5-precursor mission is “S5P”.
File_Class

NC_STRING

The file class of the output. Values are taken from the tailoring of the EO file format tailoring for S5P [RD25,
section 4.1.2].
File_Type‘%(shortname)s’ (dynamic)

NC_STRING

Following the EO file format tailoring for S5P [RD25, sections 4.1.3.1 and 4.1.3.2].
File_Version

0 (dynamic)

NC_INT

The file version information is not part of the file name conventions for S5P. If a file version number is to berecorded in this attribute, then it has to be provided by the PDGS via the job order. If provided, then thevalue is ≥ 1. If not provided the fill value is 0.
10.2.3.92

Group “validity_period” in “fixed_header”

Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/fixed_header/validity_period
Group attributes attached to validity_period
Name

Value

Type

objectType‘Validity_Period’ (static)

NC_STRING

Validity_Start

NC_STRING

The value is the string “UTC=” concatenated with the time_coverage_start global attribute. This
attribute corresponds to the “Validity_Start” element in the “Validity_Period” XML structure in the header file.
Validity_Stop

NC_STRING

The value is the string “UTC=” concatenated with the time_coverage_end global attribute. This attributecorresponds to the “Validity_Stop” element in the “Validity_Period” XML structure in the header file.

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Group “source” in “fixed_header”

Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/fixed_header/source
Group attributes attached to source
Name

Value

Type

objectType‘Source’ (static)

NC_STRING

System‘%(processingcenter)s’ (dynamic)

NC_STRING

Name of the Ground Segment element creating the file. For Level 2 files, this is the PDGS, but for testinga different value may be used. This attribute corresponds to the “System” element in the “Source” XML
structure in the header file.
Creator‘%(processor_name)s’ (dynamic)

NC_STRING

Name of the facility or tool, within the Ground Segment element, creating the file. This attribute corresponds
to the “Creator” element in the “Source” XML structure in the header file.
Creator_Version‘%(version)s’ (dynamic)

NC_STRING

Version number of the tool that created the file. This attribute corresponds to the “Creator_Version” elementin the “Source” XML structure in the header file.
Creation_Date

NC_STRING

The start date and time of processing, as a string: “UTC=YYYY-MM-DDThh:mm:ss”. This attribute corresponds to the “Creator_Date” element in the “Source” XML structure in the header file.
10.2.3.94

Group “variable_header” in “earth_explorer_header”

Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header
Group attributes attached to variable_header
Name

Value

Type

objectType‘Variable_Header’ (static)

NC_STRING

10.2.3.95

Group “gmd:lineage” in “variable_header”

Non-quantitative quality information about the lineage of the data specified by the scope.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage
Group attributes attached to gmd:lineage
Name

Value

Type

objectType‘gmd:LI_Lineage’ (static)

NC_STRING

gmd:statement‘L2 %(product)s dataset produced by %(processingcenter)s from the S5P/TROPOMI L1B product’ (dynamic)

NC_STRING

General explanation of the data producer’s knowledge about the lineage of a dataset. Insert short descriptionof the actual Level 2 product in this string (at the %(. . . )s).
10.2.3.96

Group “gmd:processStep” in “gmd:lineage”

Information about an event or transformation in the life of the dataset including details of the algorithm andsoftware used for processing.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep

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Group attributes attached to gmd:processStep
Name

Value

Type

objectType‘gmi:LE_ProcessStep’ (static)

NC_STRING

gmd:description‘Processing of L1b to L2 %(product)s data for orbit%(orbit)d using the %(institute)s processor version%(version)s’ (dynamic)

NC_STRING

Description of the event, including related parameters or tolerances. Insert short description of the actual
Level 2 product, the orbit number, the name of the institude responsible for the CFI and the software version
in this string (at the respective %(. . . )s and %(. . . )d).
10.2.3.97

Group “gmi:output” in “gmd:processStep”

Description of the output.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:output
Group attributes attached to gmi:output
Name

Value

gmd:description

Type
NC_STRING

Short description of the output, a copy of the global ‘title’ attribute.
objectType
10.2.3.98‘gmi:LE_Source’ (static)

NC_STRING

Group “gmd:sourceCitation” in “gmi:output”

Reference to the actual filename of the output data and production date and time.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:output/gmd:sourceCitation
Group attributes attached to gmd:sourceCitation
Name

Value

Type

gmd:title‘%(logical_filename)s’ (dynamic)

NC_STRING

Output file name without extension.
objectType
10.2.3.99‘gmd:CI_Citation’ (static)

NC_STRING

Group “gmd:date” in “gmd:sourceCitation”

Production date and time of the output file.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:output/gmd:sourceCitation/gmd:dateGroup attributes attached to gmd:date
Name

Value

gmd:date

Type
NC_STRING

Production date and time of the output file. Note that the definition in the XML schema appears to allow theuse of a “CI_DateTime” instead of a “CI_Date”.
objectType
10.2.3.100‘gmd:CI_DateTime’ (static)

NC_STRING

Group “gmd:dateType” in “gmd:date”

Meaning of the reference date for the cited resource.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:output/gmd:sourceCitation/gmd:date/gmd:dateType

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Group attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘creation’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.101

Group “gmd:identifier” in “gmd:sourceCitation”

Identification of the output product.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:output/gmd:sourceCitation/gmd:identifierGroup attributes attached to gmd:identifier
Name

Value

Type

gmd:code‘%(shortname)s’ (dynamic)

NC_STRING

The product short name, a copy of the ‘ProductShortName’ attribute in ‘/METADATA/GRANULE_DESCRIPTION’.
objectType
10.2.3.102‘gmd:MD_Identifier’ (static)

NC_STRING

Group “gmi:processedLevel” in “gmi:output”

Process level of the output file.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:output/gmi:processedLevel
Group attributes attached to gmi:processedLevel
Name

Value

gmd:code‘L2’ (static)

NC_STRING

objectType‘gmd:MD_Identifier’ (static)

NC_STRING

10.2.3.103

TypeGroup “gmi:processingInformation” in “gmd:processStep”

Description of the processor in more detail.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:processingInformation
Group attributes attached to gmi:processingInformation
Name

Value

Type

objectType‘gmi:LE_Processing’ (static)

NC_STRING

10.2.3.104

Group “gmi:identifier” in “gmi:processingInformation”

Identification of the processor.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:processingInformation/gmi:identifierGroup attributes attached to gmi:identifier
Name

Value

Type

gmd:code‘%(institute)s L2 %(product)s processor, version %(version)s’ (dynamic)

NC_STRING

Descriptive name of the processor, with the %(. . . )s placeholders replaced with the responsible institute’s
name, product name and software release version.
objectType‘gmd:MD_Identifier’ (static)

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Group “gmi:softwareReference” in “gmi:processingInformation”

Reference to document describing processing software.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:processingInformation/gmi:softwareReferenceGroup attributes attached to gmi:softwareReference
Name

Value

Type

gmd:title‘%(processor_name)s processor’ (dynamic)

NC_STRING‘gmd:CI_Citation’ (static)

NC_STRING

Name of the processor.
objectType
10.2.3.106

Group “gmd:date” in “gmi:softwareReference”

Release date (compile date) of the processor.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:processingInformation/gmi:softwareReference/gmd:dateGroup attributes attached to gmd:date
Name

Value

Type

gmd:date‘%(processor_release_date)s’ (dynamic)

NC_STRING

Release date of the processor expressed as an ISO 8601 date string [RD34].
objectType
10.2.3.107‘gmd:CI_DateTime’ (static)

NC_STRING

Group “gmd:dateType” in “gmd:date”

The release date of the processor.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:processingInformation/gmi:softwareReference/gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘creation’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.108

Group “gmi:documentation#1” in “gmi:processingInformation”

Reference to the ATBD of the product.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:processingInformation/gmi:documentation#1
Group attributes attached to gmi:documentation#1
Name

Value

Type

objectType‘gmd:CI_Citation’ (static)

NC_STRING

gmd:title‘%(title_atbd)s’ (dynamic)

NC_STRING

Specification of the current release of the ATBD of the product.
10.2.3.109

Group “gmd:date” in “gmi:documentation#1”

Release date of the ATBD.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:processingInformation/gmi:documentation#1/gmd:date

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Group attributes attached to gmd:date
Name

Value

Type

gmd:date‘%(date_atbd)s’ (dynamic)

NC_STRING

Release date of the ATBD expressed as an ISO 8601 date string [RD34].
objectType
10.2.3.110‘gmd:CI_Date’ (static)

NC_STRING

Group “gmd:dateType” in “gmd:date”

Specify the type of the date of the ATBD (revision of publication).
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:processingInformation/gmi:documentation#1/gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘revision’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.111

Group “gmi:documentation#2” in “gmi:processingInformation”

Reference to the PUM of the product.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:processingInformation/gmi:documentation#2
Group attributes attached to gmi:documentation#2
Name

Value

Type

objectType‘gmd:CI_Citation’ (static)

NC_STRING

gmd:title‘%(title_pum)s’ (dynamic)

NC_STRING

Specification of the current release of the PUM of the product.
10.2.3.112

Group “gmd:date” in “gmi:documentation#2”

Release date of the PUM.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:processingInformation/gmi:documentation#2/gmd:dateGroup attributes attached to gmd:date
Name

Value

Type

gmd:date‘%(date_pum)s’ (dynamic)

NC_STRING

Release date of the PUM expressed as an ISO 8601 date string [RD34].
objectType
10.2.3.113‘gmd:CI_Date’ (static)

NC_STRING

Group “gmd:dateType” in “gmd:date”

Specify the type of the date of the PUM (revision of publication).
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:processingInformation/gmi:documentation#2/gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

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codeListValue‘revision’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.114

Group “gmi:report” in “gmd:processStep”

Short report of what occurred during the process step.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmi:report
Group attributes attached to gmi:report
Name

Value

Type

gmi:description‘Sentinel 5-precursor TROPOMI L1b processed to L2
data using the %(institute)s L2 %(product)s processor’(dynamic)

NC_STRING

Textual description of what occurred during the process step. Replace %(. . . )s as indicated.
gmi:fileType‘netCDF-4’ (static)

NC_STRING

Type of file that contains the processing report, in our case the processing report is contained in the main
output file.
gmi:name‘%(logical_filename)s.nc’ (dynamic)

NC_STRING

objectType‘gmi:LE_ProcessStepReport’ (dynamic)

NC_STRING

10.2.3.115

Group “gmd:source#1” in “gmd:processStep”

Information about the source data used in creating the data specified by the scope. Repeat group as needed,
incrementing the number of the source (after the # mark).
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmd:source#1
Group attributes attached to gmd:source#1
Name

Value

Type

objectType‘gmi:LE_Source’ (static)

NC_STRING

gmd:description

NC_STRING

Description of the input data, including L1B, L2, dynamic auxiliary input data and semi-static auxiliary
input data. Base strings are “TROPOMI L1B %s radiance product”, “TROPOMI L1B %s irradianceproduct”, “TROPOMI L2 %s product”, “Auxiliary ECMWF %s Meteorological forecast data”, “Processor %s
configuration file”, “Auxiliary %s reference data”, “Auxiliary %s algorithm lookup table”, “Auxiliary CTM %s
model input data”, “Auxiliary snow and ice input data” and “Auxiliary NPP/VIIRS cloud screening input data”.
The %s to be replaced with specific descriptors.
10.2.3.116

Group “gmi:processedLevel” in “gmd:source#1”

Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmd:source#1/gmi:processedLevel
Group attributes attached to gmi:processedLevel
Name

Value

Type

gmd:code

Empty!

NC_STRING

objectType‘gmd:MD_Identifier’ (static)

NC_STRING

10.2.3.117

Group “gmd:sourceCitation” in “gmd:source#1”

Reference to the actual filename of the input data.

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Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmd:source#1/gmd:sourceCitation
Group attributes attached to gmd:sourceCitation
Name

Value

Type

objectType‘gmd:CI_Citation’ (static)

NC_STRING

10.2.3.118

Group “gmd:date” in “gmd:sourceCitation”

Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmd:source#1/gmd:sourceCitation/gmd:dateGroup attributes attached to gmd:date
Name

Value

gmd:date

Type
NC_STRING

Production date and time of the input file(s) in this group expressed as an ISO 8601 date-time string [RD34].
Note that the definition in the XML schema appears to allow the use of a “CI_DateTime” instead of a
“CI_Date”.
objectType
10.2.3.119‘gmd:CI_Date’ (static)

NC_STRING

Group “gmd:dateType” in “gmd:date”

Meaning of the reference date for the cited resource.
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmd:source#1/gmd:sourceCitation/gmd:date/gmd:dateTypeGroup attributes attached to gmd:dateType
Name

Value

Type

codeList‘http://www.isotc211.org/2005/resources/Codelist/
gmxCodelists.xml#CI_DateTypeCode’ (static)

NC_STRING

codeListValue‘creation’ (static)

NC_STRING

objectType‘gmd:CI_DateTypeCode’ (static)

NC_STRING

10.2.3.120

Group “gmd:title” in “gmd:sourceCitation”

Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmd:source#1/gmd:sourceCitation/gmd:title
Group attributes attached to gmd:title
Name

Value

gco:characterStringType
NC_STRING

Textual description of the input file group (same as the “gmd:description” attribute in the “gmi:LE_Source” object).
10.2.3.121

Group “gmd:alternateTitle#1” in “gmd:sourceCitation”

All filenames in this group, in case more files of a particular file type are delivered, for instance for meteorologicalor model input. Repeat group as needed, incrementing the number of the input file (after the # mark).
Attributes in AER_AI/METADATA/ESA_METADATA/earth_explorer_header/variable_header/gmd:lineage/
gmd:processStep/gmd:source#1/gmd:sourceCitation/gmd:alternateTitle#1

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Group attributes attached to gmd:alternateTitle#1
Name

Value

Type

gmx:FileName

Empty!

NC_STRING

The basename of the input file.

11

Units

The units attribute originates from the NetCDF-4 users guide [ER7]. This means that the use of this attributeis integral to the use of NetCDF-4 itself, and that the use of the units attribute in the NetCDF-4 users guide isa hard requirement. The NetCDF-4 users guide [ER7] strongly suggests to use the UDUnits [ER10] package
to handle units. The CF metadata conventions reinforce this requirement [ER5, sections 1.3 and 3.1].
Making the UDUnits package [ER10] a requirement, and thereby forcing all units to be compliant with formal
SI units3 is a good thing for consistency and will help avoid confusion in the long run. In the short term it will
require adjustments within the earth observation community, as many of the units that the user community is
accustomed to are not SI, and are therefore not available within the UDUnits package. The MAG has decided
that Sentinel 5 precursor will represent all level 2 output in SI units. In particular, all column amounts will begiven in mol m−2 .
To make it easier for end-users to adjust to these ‘new’ units, conversion factors are attached to theappropriate variables.
multiplication_factor_to_convert_to_molecules_percm2 Multiply the contents of the variable with thisscale factor (6.02214 × 10+19 ) to obtain columns in molecules cm−2
multiplication_factor_to_convert_to_DU Multiply the contents of the variable with this scale factor (2241.15)
to obtain columns in DU.
multiplication_factor_to_convert_to_photons_persecond_pernm_percm2_persr Multiply the contentsof the variable with this scale factor (6.02214 × 10+19 ) to obtain a radiance in photons s−1 nm−1 cm−2 sr−1 .

12Quality Assurance parameters

The Level 2 output will include automated quality assurance parameters. These include ‘event counters’ foreach of the flags defined in the processing quality flags, see tables 11 and 12. These processing quality flags
are made uniform across all products, and include flags that may not be applicable to a particular algorithm.
We still count all flags, so this list is the same for all products, a list is provided in table 4.
In addition to these ‘event counters’, we also store a histogram of the main parameters. Storing a histogramof retrieved values is easy during processing, and allows for continuous statistical quality monitoring of theretrieval. It also makes it easy to collect histograms of S5P/TROPOMI data for longer periods. The bins for thehistogram depend on the parameter in the Level 2 product, and are defined in the configuration file.
In addition to the histogram an approximation of a probability density function can be created:"#(x j − xi )2
1 N cos δgeo,i√
fpdf (x j ) = ∑exp
N i=0 σi 2π
2σi2

(7)

This is a discrete approximation of a continuous probability density function, for discrete values x j for all
successful retrievals i = 1, . . . , N . The value of cos δgeo,i is used to make the result less sensitive to therelative oversampling of S5P at high latitude.
The mission performance center for Sentinel 5 precursor maintains a record of quality control/quality
assurance parameters for monitoring purposes.

3

And some deeply entrenched non-SI units such as DU.

Description
Number of ground pixels in the file.

number_of_processed_pixels

Number of ground pixels where a retrieval was attempted. This is thenumber_of_groundpixels minus the pixels that were rejected on trivial
grounds, such as the solar zenith angle.

number_of_successfully_processed_pixels

Number of ground pixels where a retrieval was successful.

number_of_rejected_pixels_not_enough_spectrum

Number of ground pixels where a retrieval was not attempted because too
many spectral pixels were flagged as bad.

number_of_failed_retrievals

Number of pixels that were attempted but failed.

number_of_ground_pixels_with_warnings

Number of pixels with one or more warnings.

number_of_missing_scanlines

Number of scanlines that are missing from the input, presumably transmission
errors.

number_of_radiance_missing_occurrences

Number of ground pixels where “the number of spectral pixels in the radiancedue to flagging is too small to perform the fitting” occurred.

number_of_irradiance_missing_occurrences

Number of ground pixels where “the number of spectral pixels in the irradiancedue to flagging is too small to perform the fitting” occurred.

number_of_input_spectrum_missing_occurrences

Number of ground pixels where “the reflectance spectrum does not containenough points to perform the retrieval. This is different from (ir)radiance_missing in that the missing points may not be aligned” occurred.

number_of_reflectance_range_error_occurrences

Number of ground pixels where “any of the reflectances is out of bounds(R < 0 or R > Rmax )” occurred.

number_of_ler_range_error_occurrences

Number of ground pixels where “lambert-equivalent reflectivity out of range
error” occurred.

number_of_snr_range_error_occurrences

Number of ground pixels where “too low signal to noise to perform retrieval”
occurred.

number_of_sza_range_error_occurrences

Number of ground pixels where “solar zenith angle out of range, maximum
value from configuration” occurred.

number_of_vza_range_error_occurrences

Number of ground pixels where “viewing zenith angle out of range, maximum
value from configuration” occurred.

number_of_lut_range_error_occurrences

Number of ground pixels where “extrapolation in lookup table (airmass factor,
cloud radiances)” occurred.

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issues, especially given the total number of pixels in a S5P/TROPOMI granule.

Description

number_of_ozone_range_error_occurrences

Number of ground pixels where “ozone column significantly out of range of
profile climatology” occurred.

number_of_wavelength_offset_error_occurrences

Number of ground pixels where “wavelength offset exceeds maximum from
configuration” occurred.

number_of_initialization_error_occurrences

Number of ground pixels where “an error occurred during the processingof the pixel, no output was generated. The following errors raise this flag:
Mismatch between irradiance and radiance wavelengths; The on-grounddistance between band 1 and band 2 ground pixels exceeds a threshold
set in the configuration. Derived a-priori information does not validate, noprocessing is possible” occurred.

number_of_memory_error_occurrences

Number of ground pixels where “memory allocation or deallocation error”
occurred.

number_of_assertion_error_occurrences

Number of ground pixels where “error in algorithm detected during assertion”
occurred.

number_of_io_error_occurrences

Number of ground pixels where “error detected during transfer of data between
algorithm and framework” occurred.

number_of_numerical_error_occurrences

Number of ground pixels where “general fatal numerical error occurred during
inversion” occurred.

number_of_lut_error_occurrences

Number of ground pixels where “error in accessing the lookup table” occurred.

number_of_ISRF_error_occurrences

Number of ground pixels where “error detected in the input instrument spectral
response function input data” occurred.

number_of_convergence_error_occurrences

Number of ground pixels where “the main algorithm did not converge” occurred.

number_of_cloud_filter_convergence_error_occurrences

Number of ground pixels where “the cloud filter did not converge” occurred.

number_of_max_iteration_convergence_error_occurrences

Number of ground pixels where “no convergence because retrieval exceeds
maximum number of iterations. Maximum value from configuration” occurred.

number_of_aot_lower_boundary_convergence_error_occurrences

Number of ground pixels where “no convergence because the aerosol optical
thickness crosses lower boundary twice in succession” occurred.

number_of_other_boundary_convergence_error_occurrences

Number of ground pixels where “no convergence because a state vector
element crosses boundary twice in succession. Note that a separate failure
flag is defined for non-convergence due to crossing of lower AOT boundary”
occurred.

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Description

number_of_geolocation_error_occurrences

Number of ground pixels where “geolocation out of range” occurred.

number_of_ch4_noscat_zero_error_occurrences

Number of ground pixels where “the CH4 column retrieved by the nonscattering CO algorithm from the weak band or strong band is 0” occurred.

number_of_h2o_noscat_zero_error_occurrences

Number of ground pixels where “the H2 O column retrieved by the nonscattering CO algorithm from the weak band or strong band is 0” occurred.

number_of_max_optical_thickness_error_occurrences

Number of ground pixels where “maximum optical thickness exceeded during
iterations” occurred.

number_of_aerosol_boundary_error_occurrences

Number of ground pixels where “boundary hit of aerosol parameters at last
iteration” occurred.

number_of_boundary_hit_error_occurrences

Number of ground pixels where “fatal boundary hit during iterations” occurred.

number_of_chi2_error_occurrences

Number of ground pixels where “χ 2 is not-a-number or larger than 1010 ”
occurred.

number_of_svd_error_occurrences

Number of ground pixels where “singular value decomposition failure” occurred.

number_of_dfs_error_occurrences

Number of ground pixels where “degree of freedom is not-a-number” occurred.

number_of_radiative_transfer_error_occurrences

Number of ground pixels where “errors occurred during the radiative transfer
computations, no processing possible” occurred.

number_of_optimal_estimation_error_occurrences

Number of ground pixels where “errors occurred during the optimal estimation,
processing has been terminated” occurred.

number_of_profile_error_occurrences

Number of ground pixels where “flag that indicates if there were any errors
during the computation of the ozone profile” occurred.

number_of_cloud_error_occurrences

Number of ground pixels where “no cloud data” occurred.

number_of_model_error_occurrences

Number of ground pixels where “forward model failure” occurred.

number_of_number_of_input_data_points_too_low_error_occurrences

Number of ground pixels where “not enough input ozone columns to calculatea tropospheric column” occurred.

number_of_cloud_pressure_spread_too_low_error_occurrences

Number of ground pixels where “cloud pressure variability to low to estimate
a tropospheric column” occurred.

number_of_cloud_too_low_level_error_occurrences

Number of ground pixels where “clouds are too low in the atmosphere to
assume sufficient shielding” occurred.

number_of_generic_range_error_occurrences

Number of ground pixels where “generic range error” occurred.

number_of_generic_exception_occurrences

Number of ground pixels where “catch all generic error” occurred.

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Description

number_of_input_spectrum_alignment_error_occurrences

Number of ground pixels where “input radiance and irradiance spectra are notaligned correctly” occurred.

number_of_abort_error_occurrences

Number of ground pixels where “not processed because processor aborted
prematurely (time out or user abort)” occurred.

number_of_wrong_input_type_error_occurrences

Number of ground pixels where “wrong input type error, mismatch between
expectation and received data” occurred.

number_of_wavelength_calibration_error_occurrences

Number of ground pixels where “an error occurred in the wavelength calibration of this pixel” occurred.

number_of_coregistration_error_occurrences

Number of ground pixels where “no colocated pixels found in a supportingband” occurred.

number_of_slant_column_density_error_occurrences

Number of ground pixels where “slant column fit returned error, no values canbe computed” occurred.

number_of_airmass_factor_error_occurrences

Number of ground pixels where “airmass factor could not be computed” occurred.

number_of_vertical_column_density_error_occurrences

Number of ground pixels where “vertical column density could not be computed” occurred.

number_of_signal_to_noise_ratio_error_occurrences

Number of ground pixels where “the signal to noise ratio for this spectrum is
too low for processing” occurred.

number_of_configuration_error_occurrences

Number of ground pixels where “error while parsing the configuration” occurred.

number_of_key_error_occurrences

Number of ground pixels where “key does not exist” occurred.

number_of_saturation_error_occurrences

Number of ground pixels where “saturation in input spectrum” occurred.

number_of_max_num_outlier_exceeded_error_occurrences

Number of ground pixels where “the number of outliers detected in the DOAS
fit exceeds a maximum set for healthy spectra. ” occurred.

number_of_solar_eclipse_filter_occurrences

Number of ground pixels where “solar eclipse” occurred.

number_of_cloud_filter_occurrences

Number of ground pixels where “the cloud filter triggered causing the pixel tobe skipped” occurred.

number_of_altitude_consistency_filter_occurrences

Number of ground pixels where “too large difference between ECMWF altitude
and DEM altitude value” occurred.

number_of_altitude_roughness_filter_occurrences

Number of ground pixels where “too large standard deviation of altitude in
DEM” occurred.

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Description

number_of_sun_glint_filter_occurrences

Number of ground pixels where “for pixels over water, viewing direction inside
sun glint region. Definition of sun glint angle and threshold value from ATBD”
occurred.

number_of_mixed_surface_type_filter_occurrences

Number of ground pixels where “pixel contains land and water areas (e.g.
coastal pixel)” occurred.

number_of_snow_ice_filter_occurrences

Number of ground pixels where “pixel contains snow/ice: Snow/ice flag according to dynamic input OR climatological surface albedo at VIS wavelengthis larger than 0.5” occurred.

number_of_aai_filter_occurrences

Number of ground pixels where “AAI smaller than 2.0” occurred.

number_of_cloud_fraction_fresco_filter_occurrences

Number of ground pixels where “pixel contains clouds: The FRESCO effective
cloud fraction is larger than threshold. Threshold value from ATBD” occurred.

number_of_aai_scene_albedo_filter_occurrences

Number of ground pixels where “pixel contains clouds: The difference between
scene albedo at 380 nm from AAI calculation and the climatologcal surface
albedo exceeds threshold. Threshold value from ATBD. This test filters out
clouds” occurred.

number_of_small_pixel_radiance_std_filter_occurrences

Number of ground pixels where “pixel contains clouds: Standard deviationof radiances in small-pixel column exceeds threshold. Threshold value from
ATBD” occurred.

number_of_cloud_fraction_viirs_filter_occurrences

Number of ground pixels where “pixel contains clouds: The cloud fraction
from VIIRS / NPP exceeds theshold. Threshold value from ATBD” occurred.

number_of_cirrus_reflectance_viirs_filter_occurrences

Number of ground pixels where “pixel contains clouds: Cirrus reflectance fromVIIRS / NPP exceeds threshold. Threshold value from ATBD” occurred.

number_of_cf_viirs_swir_ifov_filter_occurrences

Number of ground pixels where “fraction of cloudy VIIRS pixels wihtin S5P
SWIR ground pixel exceeds a priori threshold from configuration” occurred.

number_of_cf_viirs_swir_ofova_filter_occurrences

Number of ground pixels where “fraction of cloudy VIIRS pixels wihtin S5P
SWIR OFOVa exceeds a priori threshold from configuration” occurred.

number_of_cf_viirs_swir_ofovb_filter_occurrences

Number of ground pixels where “fraction of cloudy VIIRS pixels wihtin S5P
SWIR OFOVb exceeds a priori threshold from configuration” occurred.

number_of_cf_viirs_swir_ofovc_filter_occurrences

Number of ground pixels where “fraction of cloudy VIIRS pixels wihtin S5P
SWIR OFOVc exceeds a priori threshold from configuration” occurred.

number_of_cf_viirs_nir_ifov_filter_occurrences

Number of ground pixels where “fraction of cloudy VIIRS pixels wihtin S5P
NIR ground pixel exceeds a priori threshold from configuration” occurred.

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Description

number_of_cf_viirs_nir_ofova_filter_occurrences

Number of ground pixels where “fraction of cloudy VIIRS pixels wihtin S5PNIR OFOVa exceeds a priori threshold from configuration” occurred.

number_of_cf_viirs_nir_ofovb_filter_occurrences

Number of ground pixels where “fraction of cloudy VIIRS pixels wihtin S5PNIR OFOVb exceeds a priori threshold from configuration” occurred.

number_of_cf_viirs_nir_ofovc_filter_occurrences

Number of ground pixels where “fraction of cloudy VIIRS pixels wihtin S5PNIR OFOVc exceeds a priori threshold from configuration” occurred.

number_of_refl_cirrus_viirs_swir_filter_occurrences

Number of ground pixels where “average VIIRS cirrus reflectance within SWIR
ground pixel exceeds a priori threshold from configuration” occurred.

number_of_refl_cirrus_viirs_nir_filter_occurrences

Number of ground pixels where “average VIIRS cirrus reflectance within NIR
ground pixel exceeds a priori threshold from configuration” occurred.

number_of_diff_refl_cirrus_viirs_filter_occurrences

Number of ground pixels where “difference in VIIRS average cirrus reflectance between SWIR and NIR ground pixel exceeds a priori threshold from
configuration” occurred.

number_of_ch4_noscat_ratio_filter_occurrences

Number of ground pixels where “the ratio between [CH4 ]weak and [CH4 ]strong
is below or exceeds a priori thresholds from configuration” occurred.

number_of_ch4_noscat_ratio_std_filter_occurrences

Number of ground pixels where “the standard deviation of [CH4 ]weak /[CH4]strong within the SWIR pixel and the 8 neighbouring pixels exceeds a priori
threshold from configuration” occurred.

number_of_h2o_noscat_ratio_filter_occurrences

Number of ground pixels where “the ratio between [H2 O ]weak and [H2 O ]strong
is below or exceeds a priori thresholds from configuration” occurred.

number_of_h2o_noscat_ratio_std_filter_occurrences

Number of ground pixels where “the standard deviation of [H2 O ]weak /[H2 O]strong within the SWIR pixel and the 8 neigbouring pixels exceeds a priori
threshold from configuration” occurred.

number_of_diff_psurf_fresco_ecmwf_filter_occurrences

Number of ground pixels where “difference between the FRESCO apparent
surface pressure and the ECMWF surface pressure exceeds a priori thresholdfrom configuration” occurred.

number_of_psurf_fresco_stdv_filter_occurrences

Number of ground pixels where “the standard deviation of the FRESCO
apparent surface pressure in the NIR pixel and the 8 surrounding pixels
exceeds a priori threshold from configuration” occurred.

number_of_ocean_filter_occurrences

Number of ground pixels where “the ground pixel is over ocean (and ocean
glint retrievals are not switched on)” occurred.

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Description

number_of_time_range_filter_occurrences

Number of ground pixels where “time is out of the range that is to be processed”
occurred.

number_of_pixel_or_scanline_index_filter_occurrences

Number of ground pixels where “not processed because pixel index does notmatch general selection criteria” occurred.

number_of_geographic_region_filter_occurrences

Number of ground pixels where “pixel falls outside the specified regions ofinterest” occurred.

number_of_input_spectrum_warning_occurrences

Number of ground pixels where “number of good pixels in radiance, irradianceor calculated reflectance below threshold from configuration” occurred.

number_of_wavelength_calibration_warning_occurrences

Number of ground pixels where “offset from wavelength fit is larger than limit
set in configuration” occurred.

number_of_extrapolation_warning_occurrences

Number of ground pixels where “pressure or temperature outside cross section
LUT range, other lookup table extrapolation” occurred.

number_of_sun_glint_warning_occurrences

Number of ground pixels where “sun glint posibility warning” occurred.

number_of_south_atlantic_anomaly_warning_occurrences

Number of ground pixels where “TROPOMI is inside the south Atlantic anomaly while taking these measurements” occurred.

number_of_sun_glint_correction_occurrences

Number of ground pixels where “A sun glint correction has been applied”
occurred.

number_of_snow_ice_warning_occurrences

Number of ground pixels where “snow/ice flag is set, i.e. using scene datafrom the cloud support product” occurred.

number_of_cloud_warning_occurrences

Number of ground pixels where “cloud filter based on FRESCO apparent
surface pressure (VIIRS not available), cloud fraction above threshold or cloudpressure adjusted to force cloud above surface. In case of Cloud product thisflag indicates the possiblity of ice-clouds” occurred.

number_of_AAI_warning_occurrences

Number of ground pixels where “possible aerosol contamination as either
indicated by the AAI (O3 profile)” occurred.

number_of_pixel_level_input_data_missing_occurrences

Number of ground pixels where “dynamic auxiliary input data (e.g.. cloud) is
missing for this ground pixel. A fallback option is used” occurred.

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Description

number_of_data_range_warning_occurrences

Number of ground pixels where “carbon monoxide column tends to negativevalues; Water column tends to negative values; Heavy water (HDO) column
tends to negative values; others. In case of the O3 product this flag indicates
VCD or effective albedo values outside a valid range. In case of the SO2 or
the HCHO product this flag indicates AMF values outside a valid range. For
O3 profile this warning indicates an out of range cost function, or an out ofrange RMS difference between retrieval and a priori” occurred.

number_of_low_cloud_fraction_warning_occurrences

Number of ground pixels where “low cloud fraction, therefore no cloud pressure retrieved” occurred.

number_of_altitude_consistency_warning_occurrences

Number of ground pixels where “difference between ECMWF surface elevationand high-resolution surface elevation exceeds threshold from configuration”
occurred.

number_of_signal_to_noise_ratio_warning_occurrences

Number of ground pixels where “signal to noise ratio in SWIR and/or NIR
band below threshold from configuration. For the O3 and HCHO products thisflag indicates an RMS above a certain threshold” occurred.

number_of_deconvolution_warning_occurrences

Number of ground pixels where “failed deconvolution irradiance spectrum (notpixel-specific, but row-specific)” occurred.

number_of_so2_volcanic_origin_likely_warning_occurrences

Number of ground pixels where “warning for SO2 BL product, UTLS products:
volcanic origin except for heavily polluted sites. For O3 profile this warning isissued in case of a large SO2 column which has an impact on the O3 profile
retrieval” occurred.

number_of_so2_volcanic_origin_certain_warning_occurrences

Number of ground pixels where “warning for SO2 BL product, UTLS products:
volcanic origin certain” occurred.

number_of_interpolation_warning_occurrences

Number of ground pixels where “warning for interpolation on partially missing
data. In this case the valid available data is used, potentially leading to a bias”
occurred.

number_of_saturation_warning_occurrences

Number of ground pixels where “saturation occurred spectrum, possibly causing biases in the retrieval” occurred.

number_of_high_sza_warning_occurrences

Number of ground pixels where “warning for high solar zenith angle. In thiscase, the processing can be performed with less final quality” occurred.

number_of_cloud_retrieval_warning_occurrences

Number of ground pixels where “warning occurring when the retrieval diagnostic indicates a degraded quality of the cloud retrieval” occurred.

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Name

Description

number_of_cloud_inhomogeneity_warning_occurrences

Number of ground pixels where “the cloud coregistration inhomogeneity parameter is above a given threshold. This warning is also set when the coregistration weight sums are less than 1” occurred.

number_of_thermal_instability_warning_occurrences

Number of ground pixels where “input spectra have been labeled with athermal instability warning flag” occurred.

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13

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Generic metadata and attributes

Metadata gives information about the satellite, algorithms, configuration as well as other parameters useful forthe interpretation of the processed data and tracing the production process of the level 2 files. The Sentinel 5
precursor product files, both for level 1B and level 2 contain a rich amount of metadata, both at the variablelevel and at the granule level. The full description of the metadata in the files for the UV Aerosol Index productis given in the file format description, in section 10.2. Here we provide some background on what can be foundin which location. The abbreviations listed in table 5 are used in the following part of this document to better
identify the nature of the attributes.
Table 5: The abbreviations used in metadata descriptions to indicate the origin of a specific attribute, and theabbreviations used to indicate the type of an attribute.
Abbreviation

Description

NUG

netCDF-4 Users Guide [ER7]CF

Climate and Forecast metadata conventions [ER5], which includes the COARDS [ER11]
conventions

ISO

ISO standards 19115, 19115-2 and 19157 [RD28, RD29, RD30]

InspireInspire directive [ER4]ACDD

ESIP-ACDD Attribute convention for dataset discovery [ER6]

CCI

Attributes requested by the ESA climate change initiative project. These largely overlap with
the ACDD attributes.

ESA

Fixed ESA Header [RD27]

S5P

Internal use – mostly for retrieval settings, possibly as an extension to ISO 19115 [RD28]

S

Attribute is a string attributeP

Attribute has the data-type of the variable with which it is associated (‘parent’ data type).

I

Attribute is an integer value

F

Attribute is a floating point value (either 32-bit or 64-bit).

T

Attribute is a CCSDS-ASCII time representation (“UTC=” + ISO 8601 [RD34])

We follow several metadata conventions in the S5P level 2 files, as can be seen in table 5. These include
ISO 19115-2 [RD29], OGC 10.157r3 [RD31], the ESA earth observation header [RD27] and the Climate
and Forecast metadata conventions [ER5]. Following ISO 19115-2 also ensures compliance with the Inspire
directive, with the provision that a few items that are optional in the ISO standard are required by Inspire. These
metadata standards prescribe the generation of XML files as side-files to the main product file. These metadata
standards are mostly intended for data discovery and data dissemination. This means that the metadata must
be ingested by a server so that it can be stored in a database. This database will end users help to find thedata they need. Ingestion of this metadata is facilitated by storing the metadata in a predefined XML format.
While it is possible to store the required XML directly in a NetCDF variable or attribute, it is hard to use these
directly to extract metadata. Using attributes for the individual metadata fields makes it far easier for users toread the metadata from their programs, as the interface becomes uniform: just netCDF-4.
The then question becomes how to store the metadata for the ISO 19115-2, OGC 10.157r3 and the ESA
earth observation header in the NetCDF datafile, in a way that facilitates automated creation of the XML side
files for ingestion into the database for dissemination en discovery. Fortunately this problem has already beensolved by the S5P L1B team, and a description can be found in the L1B input/output data specification and themetadata specification [RD2, RD33]. The short version is that the attributes in the data file can be exported
as NcML [RD42], which can be translated into the desired output using an XSLT transformation. Support
attributes are added to the data file to facilitate this. Creating such a transformation script has been declaredout of scope for the level 1B and level 2 processor CFI providers.

13.1

The Climate and Forecast conventions

The CF metadata conventions [ER5] provide guidelines for attributes for variables so that the link between dataand its geolocation and time of observation can be made automatically. Applying the CF-metadata conventions
to the output products already limits the number of choices we will have to make. Units and other attributes areS5P L2 PUM UV Aerosol Index
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already defined and some structure is provided by the CF-conventions, for instance in linking data fields withgeolocation.

13.2

NetCDF User Guide Conventions

A full description of the conventions might be found in the NetCDF user manual [ER7]]. In general, names
starting with underscore character are always reserved for use by the NetCDF library. NUG conventions are asubset of the CF-conventions.

13.3

Global attributes

Global attributes that are present at the root level of a S5p L2 product as described in section 10. These aremostly string attributes.

13.4

ESA earth observation header

The ESA earth observations file format guidelines and tailoring for S5P [RD27, RD25] specify the creationof a header file with a basic description of the contents of an output file. This header file consists of a fixedpart and a customizable variable part. The variable part contains the lineage of the product is repeated, seesection 10.2.3.43 for a description the the attributes contained in this part of the header. The fixed header is
described in tables 6 – 8.
Table 6: Metadata in the fixed header required by the ESA earth observation file format standard. The datatypes refer to the short list in table 5.
Name

Data typeDefinition

File_NameS

File name of the product without extension.

File_Description

S

Description of the file type.

Notes

S

Any type of notes/comments (multi-lines).

MissionS

Description of the mission (Fixed to “S5P”)

File_ClassS

Description of the file class. It is redundant with the File Class
element embedded in the File Name.(e.g., “NRTI”)

File_TypeS

Description of the file type, for the current product it is set to “L2__UV Aerosol Index”. It is redundant with the File Type element
embedded in the File Name.

Validity_Period

Group, see table 7

Time coverage of the data.

File_Version

I

It is redundant with the File Version element embedded in the File
Name.

SourceGroup, see table 8

Information about the ground segment facility where the productwas generated.

Table 7: Fields in the Validity_Period group. The data types refer to the short list in table 5.
Name

Data typeDefinition

Validity_Start

T

This is the UTC Validity Start Time, the same as the Validity Start
Time in the File Name and the time_coverage_start global attribute.

Validity_Stop

TThis is the UTC Validity Stop Time, the same as the Validity Stop
Time in the File Name and the time_coverage_end global attribute.

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Table 8: Fields in the source group. The data types refer to the short list in table 5.
Name

Data typeDefinition

SystemS

Name of the Ground Segment element creating the file.

CreatorS

Name of the facility or tool, within the Ground Segment element,
creating the file.

Creator_Version

S

Version of the tool.

Creation_Date

TThis is the UTC Creation Date. This field also appears in the filename and in the date_created global attribute.

13.5

Inspire directive

INSPIRE is based on the infrastructures for spatial information established and operated by the 27 Member
States of the European Union. The INSPIRE directive came into force on 15 May 2007 and will be developed
in several stages until a complete release with due date set in 2019. The INSPIRE directive aims to create aEuropean Union (EU) spatial data infrastructure. This will enable the sharing of environmental spatial information among public sector organizations and better facilitate public access to spatial information across Europe.
The European Commission issued a Metadata Regulation [RD43] which aims at setting the requirements forthe creation and maintenance of metadata for spatial data sets, spatial data set series and spatial data services
corresponding to the themes listed in the annexes of the regulation.
Since many different standard are involved, collisions may occur. The INSPIRE Metadata Implementing
Rules [RD44] define how the Regulation can be implemented using ISO 19115. As also reported in [RD33],
the conclusion of the study pointed out the following:
1. The conformance of an ISO 19115 metadata set to the ISO 19115 Core does not guarantee theconformance to INSPIRE.
2. The use of these guidelines to create INSPIRE metadata ensures that the metadata is not in conflictwith ISO 19115. However, full conformance to ISO 19115 implies the provision of additional metadata
elements which are not required by INSPIRE.

13.6

ISO and OGC standards

Two ISOs standards useful for the description of collection of Earth Observation products and to the descriptionof individual EO products are ISO 19115-2 [RD29] and ISO 19156 [RD45], respectively. However, these twoISOs do not provide any encoding syntax but they are merely conceptual models. On the other hand, standards
that provide encoding and XML schema for describing, validating and exchanging metadata about geographic
datasets and for observations and measurements are:
1. ISO 19139 [RD37]
2. OGC 10-025C [RD46]
3. OGC 10-157 [RD31]
Full description of all above mentioned standard is not part of this document. The S5p L01B evelopment
team have addressed and analyzed the complex structure of the application of all those ISOs and OGC
standard in the S5P L01B metadata specification [RD33].

13.7

Attributes

In Table 10 a list of attributes that can be appended to variables in S5p products. Not all of these attributes will
be used on all variables, but for each variables an appropriate selection is made. The different types with theirrespective abbreviations are shown in Table 5. The NetCDF attribute _FillValue which represents missingor undefined data can assume the default values listed in Table 9.

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Table 9: netCDF-4 type definitions and fill values. In order to avoid rounding errors, it is recommended touse the hexadecimal notation when specifying fill values for float and double types. Note that these are thenetCDF-4 default fill values, there should be no need to specify these values explicitly. In some cases the fillvalue for float or double variables may fall within the valid range of a variable. For those cases an explicit fillvalue must be set, the value −9.9692099683868690 × 1036 (hex: -0x1.ep+122) is recommended for thesecases.
Type

Description

Fill value

−127
255
−3276765535−2147483647
4294967295
9.9692099683868690 × 1036 (hex: 0x1.ep+122)
9.9692099683868690 × 1036 (hex: 0x1.ep+122)byte

8-bit signed integerubyte

8-bit unsigned integershort

16-bit signed integer

ushort16-bit unsigned integerint

32-bit signed integeruint

32-bit unsigned integer

float

32-bit floating point

double64-bit floating point

Table 10: Attributes for variables used in S5p netCDF-4 files. The data types refer to the short list in table 5.
Nameancillary_variables

Type

Std.

Description

S

CF

Identifies a variable that contains closely associated data, e.g.
the measurement uncertainties of instrument data.

boundsS

CF

Connects a boundary variable to a coordinate variable.

cell_measures

S

CF

Identifies variables that contain cell areas or volumes. Thiscan be used to connect approximate ground pixel coverage in
km2 to data-fields.

comment

S

CF

Miscellaneous information about the data or methods used to
produce it.

coordinates

S

CF

Identifies auxiliary coordinate variables, providing a connection
between data and geolocation, time.

_FillValueP

NUG

Value to represent missing or undefined data. Recommended(default) values are given in table 9.

flag_masks

P

CF

Provides a list of bit fields expressing Boolean or enumerated
flags.

flag_meanings

S

CF

Use in conjunction with flag_values to provide descriptive
words or phrases for each flag value.

flag_values

P

CF

Provides a list of the flag values. Use in conjunction with
flag_meanings.

formulaS

CF

formula_terms

S

CF

Formula to calculate the values for an adaptive grid, for instance for a dimensionless vertical coordinate. Example:“hyam hybm (mlev=hyam+hybm*aps)”.
Identifies variables that correspond to the terms in a formula,for instance for a dimensionless vertical coordinate. Example:“ap: hyam b: hybm ps: aps”

institution

S

CF

Specifies where the original data was produced.

long_nameS

CF

A descriptive name that indicates a variable’s content. This
name is not standardized.

positive

S

CF

Direction of increasing vertical coordinate value (‘up’ for z in mor ‘down’ for p in hPa).

references

S

CF

References that describe the data or methods used to produceit.

sourceS

CF

Method of production of the original data.

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Table 10: Attributes for variables used in S5p netCDF-4 files (continued).
Name

Type

Std.

Description

standard_error_multiplierF

CF

If a data variable with a standard_name modifier of standard_error has this attribute, it indicates that the values are thestated multiple of one standard error. The only allowed value
for S5p files is 1, used only to disambiguate.

standard_nameSCF

A standard name that references a description of a variable’s
content in the standard name table.

units

S

CF

Units of a variable’s content. See section 11 for a detailed
discussion.

valid_max

P

NUG

Largest valid value of a variable.

valid_minP

NUG

Smallest valid value of a variable.

valid_range

P[2]

NUG

Smallest and largest valid values of a variable. This attributeshould not be combined with either valid_min or valid_max

AFlag descriptions

The following tables describe the Measurement flags, Processing quality flags (processing failures and filter
conditions, errors and warnings) and surface classifications.

#

Short name

Description

Algorithm

0

success

No failures, output contains value. Warnings still possible.

All1

radiance_missing

The number of spectral pixels in the radiance due to flagging is too small to performthe fitting.

All

2irradiance_missing

The number of spectral pixels in the irradiance due to flagging is too small toperform the fitting.

All3

input_spectrum_missing

The reflectance spectrum does not contain enough points to perform the retrieval.
This is different from (ir)radiance_missing in that the missing points may not bealigned.

All4reflectance_range_error

Any of the reflectances is out of bounds (R < 0 or R > Rmax ).

FRESCO5

ler_range_error

Lambert-equivalent reflectivity out of range error.

CO, CH4

6

snr_range_error

Too low signal to noise to perform retrieval.

CO7

sza_range_error

Solar zenith angle out of range, maximum value from configuration.

All8

vza_range_error

Viewing zenith angle out of range, maximum value from configuration.

Development phase only

lut_range_error

Extrapolation in lookup table (airmass factor, cloud radiances).

NO2

ozone_range_error

Ozone column significantly out of range of profile climatology.

Total O3 column

11

wavelength_offset_error

Wavelength offset exceeds maximum from configuration.

FRESCO, NO2

12initialization_error

An error occurred during the processing of the pixel, no output was generated.
The following errors raise this flag: Mismatch between irradiance and radiancewavelengths; The on-ground distance between band 1 and band 2 ground pixels
exceeds a threshold set in the configuration. Derived a-priori information does not
validate, no processing is possible.

All

13

memory_error

Memory allocation or deallocation error.

CO, CH4

14

assertion_error

Error in algorithm detected during assertion.

CO15

io_error

Error detected during transfer of data between algorithm and framework.

CO, ALH, CH4 , O3 profile

16

numerical_error

General fatal numerical error occurred during inversion.

CO, FRESCO

17

lut_error

Error in accessing the lookup table.

CH4

18

ISRF_error

Error detected in the input instrument spectral response function input data.

CH4

19

convergence_error

The main algorithm did not converge.

All

20

cloud_filter_convergence_error

The cloud filter did not converge.

CO

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Table 11: Processing quality flags, errors, processing failures and filter conditions for S5P Level 2. Warnings are listed in table 12. The value in the first column is theresult of a bitwise ‘and’ of 255 (0xFF) and the value in the “processing_quality_flags” variable.

Short name

Description

Algorithm

max_iteration_convergence_error

No convergence because retrieval exceeds maximum number of iterations. Maximum value from configuration.

ALH

22

aot_lower_boundary_convergence_error

No convergence because the aerosol optical thickness crosses lower boundary
twice in succession.

ALH

23

other_boundary_convergence_error

No convergence because a state vector element crosses boundary twice in succession. Note that a separate failure flag is defined for non-convergence due tocrossing of lower AOT boundary.

ALH

25

ch4_noscat_zero_error

The CH4 column retrieved by the non-scattering CO algorithm from the weak bandor strong band is 0.

CH4

26

h2o_noscat_zero_error

The H2 O column retrieved by the non-scattering CO algorithm from the weak bandor strong band is 0.

CH4

27

max_optical_thickness_error

Maximum optical thickness exceeded during iterations.

CH4

28

aerosol_boundary_error

Boundary hit of aerosol parameters at last iteration.

CH4

29

boundary_hit_error

Fatal boundary hit during iterations.

CH4

30

chi2_error

χ 2 is not-a-number or larger than 1010 .

CH4

31

svd_error

Singular value decomposition failure.

CH4

32

dfs_error

Degree of freedom is not-a-number.

CH4

33

radiative_transfer_error

Errors occurred during the radiative transfer computations, no processing possible.

O3 profile

34

optimal_estimation_error

Errors occurred during the optimal estimation, processing has been terminated.

O3 profile

35

profile_error

Flag that indicates if there were any errors during the computation of the ozone
profile.

O3 profile

36

cloud_error

No cloud data.

Cloud

37

model_error

Forward model failure.

Cloud, Total O3 column

38

number_of_input_data_points_too_low_error

Not enough input ozone columns to calculate a tropospheric column.

Tropospheric O3 column

39

cloud_pressure_spread_too_low_error

Cloud pressure variability to low to estimate a tropospheric column.

Tropospheric O3 column

40

cloud_too_low_level_error

Clouds are too low in the atmosphere to assume sufficient shielding.

Tropospheric O3 column

41

generic_range_error

Generic range error.

All

42

generic_exception

Catch all generic error.

All

43

input_spectrum_alignment_error

Input radiance and irradiance spectra are not aligned correctly.

All

44

abort_error

Not processed because processor aborted prematurely (time out or user abort)All

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Table 11: Processing quality flags, errors, processing failures and filter conditions for S5P Level 2 (continued).

Short name

Description

Algorithm

wrong_input_type_error

Wrong input type error, mismatch between expectation and received data.

All

46

wavelength_calibration_error

An error occurred in the wavelength calibration of this pixel

All

47

coregistration_error

No colocated pixels found in a supporting band

All

51

signal_to_noise_ratio_error

The signal to noise ratio for this spectrum is too low for processing

All

52

configuration_error

Error while parsing the configuration

All

53

key_error

Key does not exist

All

54

saturation_error

Saturation in input spectrum

All

55

max_num_outlier_exceeded_error

The number of outliers detected in the DOAS fit exceeds a maximum set for healthy
spectra.

NO2

64

solar_eclipse_filter

Solar eclipse.

All

65

cloud_filter

The cloud filter triggered causing the pixel to be skipped.

CO, ALH, CH466

altitude_consistency_filter

Too large difference between ECMWF altitude and DEM altitude value.

CO, CH4

67

altitude_roughness_filter

Too large standard deviation of altitude in DEM.

CO, ALH, CH468

sun_glint_filter

For pixels over water, viewing direction inside sun glint region. Definition of sun
glint angle and threshold value from ATBD.

ALH

69

mixed_surface_type_filter

Pixel contains land and water areas (e.g. coastal pixel).

ALH

70

snow_ice_filter

Pixel contains snow/ice: Snow/ice flag according to dynamic input OR climatologicalsurface albedo at VIS wavelength is larger than 0.5.

ALH

71

aai_filter

AAI smaller than 2.0.

ALH

72

cloud_fraction_fresco_filter

Pixel contains clouds: The FRESCO effective cloud fraction is larger than threshold.
Threshold value from ATBD.

ALH

73

aai_scene_albedo_filter

Pixel contains clouds: The difference between scene albedo at 380 nm from AAI
calculation and the climatologcal surface albedo exceeds threshold. Thresholdvalue from ATBD. This test filters out clouds.

ALH

74

small_pixel_radiance_std_filter

Pixel contains clouds: Standard deviation of radiances in small-pixel column exceeds threshold. Threshold value from ATBD.

ALH, CH475

cloud_fraction_viirs_filter

Pixel contains clouds: The cloud fraction from VIIRS / NPP exceeds theshold.
Threshold value from ATBD.

ALH

76

cirrus_reflectance_viirs_filter

Pixel contains clouds: Cirrus reflectance from VIIRS / NPP exceeds threshold.
Threshold value from ATBD.

ALH

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Table 11: Processing quality flags, errors, processing failures and filter conditions for S5P Level 2 (continued).

Short name

Description

Algorithm

cf_viirs_swir_ifov_filter

Fraction of cloudy VIIRS pixels wihtin S5P SWIR ground pixel exceeds a priori
threshold from configuration.

CH4

78

cf_viirs_swir_ofova_filter

Fraction of cloudy VIIRS pixels wihtin S5P SWIR OFOVa exceeds a priori thresholdfrom configuration.

CH4

79

cf_viirs_swir_ofovb_filter

Fraction of cloudy VIIRS pixels wihtin S5P SWIR OFOVb exceeds a priori thresholdfrom configuration.

CH4

80

cf_viirs_swir_ofovc_filter

Fraction of cloudy VIIRS pixels wihtin S5P SWIR OFOVc exceeds a priori thresholdfrom configuration.

CH4

81

cf_viirs_nir_ifov_filter

Fraction of cloudy VIIRS pixels wihtin S5P NIR ground pixel exceeds a priori
threshold from configuration.

CH4

82

cf_viirs_nir_ofova_filter

Fraction of cloudy VIIRS pixels wihtin S5P NIR OFOVa exceeds a priori thresholdfrom configuration.

CH4

83

cf_viirs_nir_ofovb_filter

Fraction of cloudy VIIRS pixels wihtin S5P NIR OFOVb exceeds a priori thresholdfrom configuration.

CH4

84

cf_viirs_nir_ofovc_filter

Fraction of cloudy VIIRS pixels wihtin S5P NIR OFOVc exceeds a priori thresholdfrom configuration.

CH4

85

refl_cirrus_viirs_swir_filter

Average VIIRS cirrus reflectance within SWIR ground pixel exceeds a priori
threshold from configuration.

CH4

86

refl_cirrus_viirs_nir_filter

Average VIIRS cirrus reflectance within NIR ground pixel exceeds a priori thresholdfrom configuration.

CH4

87

diff_refl_cirrus_viirs_filter

Difference in VIIRS average cirrus reflectance between SWIR and NIR ground pixel
exceeds a priori threshold from configuration.

CH4

88

ch4_noscat_ratio_filter

The ratio between [CH4 ]weak and [CH4 ]strong is below or exceeds a priori thresholds
from configuration.

CH4

89

ch4_noscat_ratio_std_filter

The standard deviation of [CH4 ]weak /[CH4 ]strong within the SWIR pixel and the 8neighbouring pixels exceeds a priori threshold from configuration.

CH4

90

h2o_noscat_ratio_filter

The ratio between [H2 O ]weak and [H2 O ]strong is below or exceeds a priori thresholds
from configuration.

CH4

91

h2o_noscat_ratio_std_filter

The standard deviation of [H2 O ]weak /[H2 O ]strong within the SWIR pixel and the 8
neigbouring pixels exceeds a priori threshold from configuration.

CH4

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Table 11: Processing quality flags, errors, processing failures and filter conditions for S5P Level 2 (continued).

#

Short name

Description

Algorithm

92

diff_psurf_fresco_ecmwf_filter

Difference between the FRESCO apparent surface pressure and the ECMWF
surface pressure exceeds a priori threshold from configuration.

CH4

93

psurf_fresco_stdv_filter

The standard deviation of the FRESCO apparent surface pressure in the NIR pixel
and the 8 surrounding pixels exceeds a priori threshold from configuration.

CH4

94

ocean_filter

The ground pixel is over ocean (and ocean glint retrievals are not switched on).

CH4

95

time_range_filter

Time is out of the range that is to be processed.

All

96

pixel_or_scanline_index_filter

Not processed because pixel index does not match general selection criteria.

All

97

geographic_region_filter

Pixel falls outside the specified regions of interest.

All

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Table 11: Processing quality flags, errors, processing failures and filter conditions for S5P Level 2 (continued).

Table 12: Processing quality flags, warnings for S5P Level 2. Errors, processing failures and filter conditions are listed in table 11. If a bitwise ‘and’ of the mask value andthe value in the “processing_quality_flags“ variable is not zero, then the warning applies to the specific retrieval.
Bit #Mask (hex)

Short name

Description

Algorithm

0–7

0x000000FF

error

If non-zero an error has occurred when processing the pixel, see table 11 fordetails.

All

80x00000100

input_spectrum_warning

Number of good pixels in radiance, irradiance or calculated reflectance below
threshold from configuration.

All

0x00000200

wavelength_calibration_warning

Offset from wavelength fit is larger than limit set in configuration.

Most

0x00000400

extrapolation_warning

Pressure or temperature outside cross section LUT range, other lookup table
extrapolation.

CO, CH4110x00000800

sun_glint_warning

Sun glint posibility warning.

All

12

0x00001000

south_atlantic_anomaly_warning

TROPOMI is inside the south Atlantic anomaly while taking these measurements.

All

13

0x00002000

sun_glint_correction

A sun glint correction has been applied.

Cloud

14

0x00004000

snow_ice_warning

Snow/ice flag is set, i.e. using scene data from the cloud support product.

NO2 , Cloud

15

0x00008000

cloud_warning

Cloud filter based on FRESCO apparent surface pressure (VIIRS not available), cloud fraction above threshold or cloud pressure adjusted to force cloud
above surface. In case of Cloud product this flag indicates the possiblity of
ice-clouds.

CH4 , O3 profile, Cloud

16

0x00010000

AAI_warning

Possible aerosol contamination as either indicated by the AAI (O3 profile).

O3 profile

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Table 12: Processing quality flags, warnings for S5P Level 2 (continued).
Mask (hex)

Short name

Description

Algorithm

170x00020000

pixel_level_input_data_missing

Dynamic auxiliary input data (e.g.. cloud) is missing for this ground pixel. A
fallback option is used.

All

18

0x00040000

data_range_warning

Carbon monoxide column tends to negative values; Water column tends
to negative values; Heavy water (HDO) column tends to negative values;
others. In case of the O3 product this flag indicates VCD or effective albedo
values outside a valid range. In case of the SO2 or the HCHO product thisflag indicates AMF values outside a valid range. For O3 profile this warning
indicates an out of range cost function, or an out of range RMS difference
between retrieval and a priori.

CO, CH4 , O3 , SO2 , HCHO, O3 profile

190x00080000

low_cloud_fraction_warning

Low cloud fraction, therefore no cloud pressure retrieved.

Cloud

20

0x00100000

altitude_consistency_warning

Difference between ECMWF surface elevation and high-resolution surface
elevation exceeds threshold from configuration.

CH4

21

0x00200000

signal_to_noise_ratio_warning

Signal to noise ratio in SWIR and/or NIR band below threshold from configuration. For the O3 and HCHO products this flag indicates an RMS above acertain threshold.

CH4 , O3 , HCHO

220x00400000

deconvolution_warning

Failed deconvolution irradiance spectrum (not pixel-specific, but row-specific).

CO, CH4

23

0x00800000

so2_volcanic_origin_likely_warning

Warning for SO2 BL product, UTLS products: volcanic origin except for heavily
polluted sites. For O3 profile this warning is issued in case of a large SO2column which has an impact on the O3 profile retrieval.

SO2 , O3 profile

240x01000000

so2_volcanic_origin_certain_warning

Warning for SO2 BL product, UTLS products: volcanic origin certain.

SO2

25

0x02000000

interpolation_warning

Warning for interpolation on partially missing data. In this case the valid
available data is used, potentially leading to a bias.

All

26

0x04000000

saturation_warning

Saturation occurred spectrum, possibly causing biases in the retrieval

All

27

0x08000000

high_sza_warning

Warning for high solar zenith angle. In this case, the processing can be
performed with less final quality.

All

28

0x10000000

cloud_retrieval_warning

Warning occurring when the retrieval diagnostic indicates a degraded qualityof the cloud retrieval.

Cloud

29

0x20000000

cloud_inhomogeneity_warning

The cloud coregistration inhomogeneity parameter is above a given threshold.
This warning is also set when the coregistration weight sums are less than 1.

Cloud

30

0x40000000

thermal_instability_warning

Input spectra have been labeled with a thermal instability warning flag.

All

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Bit #Bit #

Short name

Description

0x03

Land

The pixel is over land, for more than 50 %

1

0x03

Water

The pixel is over water, for more than 50 %

2

0x03

some_water

3

0x03

coastline

00x04

mixed_surface

4

0x04

value_covers_majority_of_pixel

9

0xF9

Water+Shallow_Ocean

17

0xF9

Water+Shallow_Inland_Water

25

0xF9

Water+Ocean_Coastline-Lake_Shoreline

33

0xF9

Water+Intermittent_Water

41

0xF9

Water+Deep_Inland_Water

49

0xF9

Water+Continental_Shelf_Ocean

57

0xF9

Water+Deep_Ocean

8

0xF9

Land+Urban_And_Built-up_Land

16

0xF9

Land+Dryland_Cropland_And_Pasture

24

0xF9

Land+Irrigated_Cropland_And_Pasture

32

0xF9

Land+Mixed_Dryland-irrigated_Cropland_And_Pasture

40

0xF9

Land+Cropland-grassland_Mosaic

48

0xF9

Land+Cropland-woodland_Mosaic

56

0xF9

Land+Grassland

64

0xF9

Land+Shrubland

72

0xF9

Land+Mixed_Shrubland-grassland

80

0xF9

Land+Savanna

88

0xF9

Land+Deciduous_Broadleaf_Forest

Pixel contains water (however small the fraction), i.e. at least one of the
15 × 15 arcsecond subpixels in the SDP dataset is classified as water
Pixel is water, but contains land (coastline)
Pixel has a mixed surface type. Classification is result of highest bin, notoverwhelming majority, i.e. type covers less than 50 % of pixel surface
Pixel is dominated by surface type, i.e. type covers more than 50 % of pixel
surface
Water, shallow ocean
Water, shallow inland water (lake)
Water, mixed with land; coastline
Intermittent water, for instance the Wadden Sea
Deep inland water
Water, continental shelf ocean
Water, deep oceanLand, urban areas
Land, Dryland Cropland and Pasture
Land, Irrigated Cropland and Pasture
Land, Mixed Dryland/Irrigated Cropland and Pasture
Land, Cropland/Grassland Mosaic
Land, Cropland/Woodland Mosaic
Land, Grassland
Land, Shrubland
Land, Mixed Shrubland/Grassland
Land, Savanna
Land, Deciduous Broadleaf Forest

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Mask (hex)0

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Table 13: Surface classification for S5P Level 2. This is a combined land/water mask and surface classification data field. For land the “Global Land Cover Characteristics
Data Base Version 2.0” is used [ER8], specifically the “USGS Land Use/Land Cover System (Modified Level 2)” classification. Over water the classification from theNASA SDP toolkit [ER9], which is based on [RD36].

Bit #

Mask (hex)

Short name

Description

96

0xF9

Land+Deciduous_Needleleaf_Forest

Land, Deciduous Needleleaf Forest

104

0xF9

Land+Evergreen_Broadleaf_Forest

Land, Evergreen Broadleaf Forest

112

0xF9

Land+Evergreen_Needleleaf_Forest

Land, Evergreen Needleleaf Forest

120

0xF9

Land+Mixed_Forest

Land, Mixed Forest

128

0xF9

Land+Herbaceous_Wetland

Land, Herbaceous Wetland

136

0xF9

Land+Wooded_Wetland

Land, Wooded Wetland

144

0xF9

Land+Barren_Or_Sparsely_Vegetated

Land, Barren or Sparsely Vegetated

152

0xF9

Land+Herbaceous_Tundra

Land, Herbaceous Tundra

160

0xF9

Land+Wooded_Tundra

Land, Wooded Tundra

168

0xF9

Land+Mixed_Tundra

Land, Mixed Tundra

176

0xF9

Land+Bare_Ground_Tundra

Land, Bare Ground Tundra

184

0xF9

Land+Snow_Or_Ice

Land, Snow or Ice

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Table 13: Surface classification for S5P Level 2 (continued).

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