S5P Mission Performance Centre
Nitrogen Dioxide [L2__NO2___]
Readmedocument number
issue
date
product version
status

S5P-MPC-KNMI-PRF-NO2

Prepared by

H. J. Eskes (KNMI)
K.-U. Eichmann (IUPB)
J.-C. Lambert (BIRA-IASB)
D. Loyola (DLR)
D. Stein-Zweers (KNMI)
A. Dehn (ESA)
C. Zehner (ESA)

Reviewed byApproved by

2.4
2023-03-16
02.05.00
Released
MPC Product Lead
MPC Validation Coordinator
MPC ESL-VAL Lead
MPC ESL-L2 Lead
MPC Technical Manager
ESA Data Quality Manager
ESA Mission Manager

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Kai-Uwe Eichmann (IUPB)
J.-C. Lambert (BIRA-IASB)
T. Verhoelst (BIRA-IASB)
S. Compernolle (BIRA-IASB)
G. Pinardi (BIRA-IASB)MPC Contributors P. Valks (DLR)
J. van Geffen (KNMI)
K.F. Boersma (KNMI, WUR)
M. Sneep (KNMI)
M. ter Linden (KNMI)
L. Saavedra de Miguel (ESA/Serco)
V. Fioletov (ECCC)
C. McLinden (ECCC)
L. Lamsal (NASA)
S. Casadio (Serco)
S5PVT1
I. Ialongo (FMI)
Contributors
A. Pazmiño (LATMOS-CNRS)
F. Goutail (LATMOS-CNRS)
J.-P. Pommereau (LATMOS-CNRS)
T. Wagner (MPI-Mainz)
A. Richter (IUPB)MPC ESL-VAL Contributor
MPC ESL-VAL Lead
MPC ESL-VAL Contributor
MPC ESL-VAL Contributor
MPC ESL-VAL Contributor
MPC ESL-VAL Contributor
MPC ESL-L2 Product Contributor
MPC ESL-L2 Product Contributor
MPC ESL-L2 Product Contributor
MPC ESL-L2 Product Contributor
ESA S5p Mission Support
S5PVT, ECCC Project, AO 28536
S5PVT, ECCC Project, AO 28536
S5PVT, NASA Project, AO 40202
S5PVT, SERCO Project, AO 42807
S5PVT, HIGHVAL Project, AO 28618
S5PVT, NIDFORVal Project, AO 28607
S5PVT, NIDFORVal Project, AO 28607
S5PVT, NIDFORVal Project, AO 28607
S5PVT, TROPGRAD Project, AO 28581
S5PVT, VVS5P Project, AO 28651

signedAngelik Digitallyby Angelika Dehn
Date: 2023.03.16
a Dehn 15:03:15 +01'00'
Signatures

A. Dehn (ESA) – Data Quality Manager

signedClaus Digitallyby Claus Zehner2023.03.16
Zehner Date:
16:18:08 +01'00'
C. Zehner (ESA) – Mission Manager

1

The S5PVT AO project summaries can be found athttps://earth.esa.int/eogateway/news/announcement-of-opportunity-for-s5pvt

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Reason for change• Table 2: addition of version 01.04.00• Added/updated qa_value filter for variables:- nitrogendioxide_stratospheric_column- nitrogendioxide_total_column- nitrogendioxide_summed_total_column• Section 5 (Algorithm Change Record) updated with version
01.04.00 information: text related to the improved data quality
for anthropogenic emitted NO2 measurements• Table 2: adapting to version 02.02.00 of the processor• Section 4.1 & section 0: some text moved from section 4.1(Known Data Quality Issues) to section 0: (Solved Data
Quality Issues)• Section 5: Algorithm change record updated• Section 6.1: added format changes related to version
02.02.00• Table 2: addition of version 02.03.01• Section 4.1: last two paragraphs added• Section 4.2: last three paragraphs added• Section 6.1: format changes added, for version 02.03.01• Table 2: addition of version 02.04.00• Section 4.1 & section 4.2: some text moved from section 4.1(Known Data Quality Issues) to section 4.2: (Solved Data
Quality Issues)• Section 5: Algorithm change record updated• Section 6.1: format changes added, for version 02.04.00• Table 2: addition of reprocessed dataset with version
02.04.00• Section 7: updates with information related to gaps on the
reprocessed dataset• Section 5: text related to Reprocessed (RPRO) dataset• Table 2: addition of version 02.05.00• Section 5: addition of text related to version 02.05.00• Section 6.1: added minor format changes related to version
02.05.00

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Issue

Revision1

6

26/11/2020

2

0

05/07/2021

2

1

17/11/2021

2

2

20/07/2022

2

3

27/02/2023

2

4

16/03/2023

Date

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SummaryThis is the Product Readme File (PRF) of the Copernicus Sentinel 5 Precursor Tropospheric Monitoring
Instrument (S5P/TROPOMI) nitrogen dioxide (NO2) Level 2 data product and is applicable for the Near
Real Time (NRTI), Offline (OFFL) and Reprocessed (RPRO) timeliness products.
Product Identifier: L2__NO2___
Example filename:
S5P_NRTI_L2__NO2____20201007T202447_20201007T220617_15471_01_020200_20210515T213556.nc
S5P_OFFL_L2__NO2____20201007T202447_20201007T220617_15471_01_020200_20210515T213556.nc
S5P_RPRO_L2__NO2____20180515T173449_20180515T191619_03041_03_020400_20221129T133010.nc

The OFFL and RPRO data product has the following DOI: http://doi.org/10.5270/S5P-9bnp8q8
The Readme file describes the current processing baseline, product and quality limitations, and productavailability status. More information on this data product is available from the Sentinel product webpage:https://sentinels.copernicus.eu/web/sentinel/technical-guides/sentinel-5p/products-algorithms,
and from the TROPOMI product webpage http://www.tropomi.eu/data-products.
The data file contains the nitrogendioxide_tropospheric_column which gives the total
atmospheric NO2 column between the surface and the top of the troposphere. The respective error
estimate originating from the spectral fit and other retrieval aspects is given in the data field
nitrogendioxide_tropospheric_column_precision. As a user guideline for the data quality,a qa_value is provided with the data. In order to avoid misinterpretation of the data quality, it isrecommended at the current stage to only use those pixels with a qa_value above 0.75 (or above 0.5
in case cloud covered scenes are also of interest).
Note that the NO 2 data product may be used in different ways, and depending on the application,different data fields in the file are relevant. For details on NO2 data usage, we refer to the product user
manual [RD03]. The averaging kernels are provided in the data product file and should be used, e.g.,
for comparisons with models or profile measurements. Stratospheric NO2 columns(nitrogendioxide_stratospheric_column) and total as well as summed NO2 columns(nitrogendioxide_total_column / nitrogendioxide_summed_total_column) are provided.
For the stratospheric column, it is recommended at the current stage to use those pixels with aqa_value above 0.5. For the total and summed columns, the same recommendation as for the
tropospheric column applies.
Note: Starting from processor version 02.02.00, new improved Level 1b version 2.0 data products areused as input [RD05].
Independent validation by S5p Mission Performance Centre (MPC) Cal/Val experts and the Sentinel-5
Precursor Validation Team (S5PVT) concludes that versions 02.02.00 and 02.03.01 of the NRTI / OFFL
NO2 data are compliant with the requirements as defined in the S5P Calibration and Validation Plan
[RD01], see Table 1. The version 2 products show clear increases of the tropospheric columns anddecreases of the biases. Version 02.04.00 makes use of a Directional Lambertian Equivalent Reflectivity
climatology derived from TROPOMI observations which replaces the older OMI and GOME-2 datasets.
First verification results indicate major changes (mainly increases) over forest areas (South America,
Africa) and smaller (more neutral) average changes over Europe, US and East China.
Up to date validation results are available in the Routine Operations Consolidated Validation Reports(ROCVR) that are accessible through the MPC Validation Data Analysis Facility (VDAF) website at
http://mpc-vdaf.tropomi.eu. The ROCVR reports are issued quarterly. Reports released after September
2021 include validation results based on processor version 02.xx.xx, while previous ROCVR reports
cover validation results only for versions 01.02.xx up to 01.04.00.
Parameter
NO2

Data productStratospheric NO2

Vertical Resolution
Stratospheric column

Bias
< 10%

Random0.5x1015 molec/cm2

NO2

Tropospheric NO2

Tropospheric column

25-50%

0.7x1015 molec/cm2

Table 1: NO2 data product requirement extracted from the S5p Calibration and Validation Plan [RD01].

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Processing baseline description

Table 2 contains the history of the NO2 processor versions. Note that the processor version for NO2 is changing when there is a change to any of the products
belonging to the NL-L2 processor suite (NO2, CO, CH4, AI, ALH, O3 PR) even if the change is not affecting the NO2 product.
Processor
VersionIn operation from

In operation until

Relevant improvements

02.05.00

NRTI: orbit 28078, 2023-03-15
OFFL: orbit 28031, 2023-03-12

Current version
Current version-

02.04.00

NRTI: orbit 24697, 2022-07-20
OFFL: orbit 24655, 2022-07-17
RPRO: orbit 2818, 2018-04-30

Orbit 28074, 2023-03-15
Orbit 28030, 2023-03-12
Orbit 24779, 2022-07-25

02.03.01

NRTI: orbit 21223, 2021-11-17
OFFL: orbit 21188, 2021-11-14

Orbit 24697, 2022-07-20
Orbit 24654, 2022-07-17

02.02.00

NRTI: orbit 19308, 2021-07-05
OFFL: orbit 19258, 2021-07-01

Orbit 21222, 2021-11-17
Orbit 21187, 2021-11-14

Small OFFL bug fix for qa_value, only affecting snow/ice covered pixels (see section
5)This version makes use of a Directional Lambertian Equivalent Reflectivity (DLER)
climatology derived from TROPOMI observations ([RD02]) which replaces the older
OMI and GOME-2 datasets used in versions 1.0.2 – 2.3.1.

Note 1: It is recommended to use the RPRO products in the orbit range 24655 - 24779,
period for which also OFFL products are available. This, in order to avoid products withpossible instabilities, because generated during the first days of the operational switch toversion 2.4.0
Note 2: Starting from processor version 2.4.0, new improved Level 1b version 2.1 data
products are used as input [RD05].
Few bugs fixed (see section 4.2)
Minor format changes (see section 6.1)
- New O2-O2 cloud algorithm integrated (this is the OMI cloud algorithm using the O2–O2
collision induced absorption around 477 nm). These cloud parameters are retrieved andstored in the output NO2 product, but not used in the conversion from NO2 slant column
to vertical column (AMF calculations). This is foreseen for future versions.
- The regridded FRESCO cloud parameters are written to the NO 2 product as well.
- In the NO2 window the surface albedo is now adjusted to avoid negative cloud fractions
while maintaining radiance closure. This leads to a significant increase of
tropospheric NO2 for cloud-free scenes on top of the increase for small cloud coverpixels in version 01.04.00 related to the FRESCO cloud retrieval upgrade. Similarly, forfully clouded scenes with bright clouds, the cloud albedo is adjusted, rather than allowing
over-unity cloud fraction.
- Cloud parameters used for the AMF calculation (for converting NO2 slant columns to NO2
vertical columns): for every ground pixel, the actual parameters used are written to the‘old’ cloud variables. In this version, version 2.2, the cloud parameters are a copy of the
FRESCO parameters. In the future, there will be rules to use O2-O2 or FRESCO cloudparameters depending on under which scene conditions they work best.

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Implementation of a ‘spike removal’ algorithm, with a high positive impact on pixels thatare not flagged for saturation or blooming in the L1b product, but nevertheless influenced,
and on pixels over the South Atlantic Anomaly.
Correct the unit of the ghost column in the NRTI product.
OFFL only: metadata fix (in Chemistry Transport Model TM5 loop).

Note: Starting from processor version 2.2.0, new improved Level 1b version 2.0 data
products are used as input [RD05].
- The FRESCO-S cloud retrieval was updated (this is an auxiliary input for the NO 2
processing), resulting in an overall reduction of the cloud pressure, and a substantial
increase of NO2 in the retrievals in polluted regions.
- Users should be careful when performing trend studies using previous versions andversion 01.04.xx (see section 5). A full mission reprocessing will be performed toharmonize the dataset.

01.04.00

NRTI: orbit 16259, 2020-12-02
OFFL: orbit 16213, 2020-11-29

Orbit 19306, 2021-07-05
Orbit 19257, 2021-07-01

01.03.02

NRTI: orbit 8906, 2019-07-03
OFFL: orbit 8815, 2019-06-26

Orbit 16256, 2020-12-02
Orbit 16212, 2020-11-29-

No changes with respect to previous version

01.03.01

NRTI: orbit 8000, 2019-04-30
OFFL: orbit 7907, 2019-04-23

Orbit 8906, 2019-07-03
Orbit 8814, 2019-06-26-

No changes with respect to previous version

01.03.00

NRTI: orbit 07519, 2019-03-27
OFFL: orbit 7425, 2019-03-20

Orbit 7906, 2019-04-23
Orbit 7999, 2019-04-30-

The FRESCO-S cloud retrieval has been updated (see section 5)
Definition of qa_value improved (see section 5)
New variables added (see section 6.1)

01.02.02

NRTI: orbit 5931, 2018-12-05
OFFL: orbit 5833, 2018-11-28
RPRO: orbit 2818, 2018-04-30

Orbit 7518, 2019-03-27
Orbit 7424, 2019-03-20
Orbit 5235, 2018-10-17-

No changes with respect to previous version-

Implementation of a "destriping" algorithm to remove across-track biases between theindividual viewing angles (see section 5)
Improvement of the retrieval for high Solar Zenith Angles (SZA) and polar regions (seesection 5)
Better algorithm for the computation of the thermal tropopause level resulting in a more
realistic distribution of tropopause pressures (see section 5)
New variable added (see section 6.1)
Definition of qa_value improved for good quality retrievals over snow-ice (see section
5)

01.02.00

NRTI: orbit 5336, 2018-10-24
OFFL: orbit 5236, 2018-10-17

Orbit 5929, 2018-12-05
Orbit 5832, 2018-11-28-

01.01.00

NRTI: orbit 3947, 2018-07-18
OFFL: orbit 3848, 2018-07-11

Orbit 5333, 2018-10-24
Orbit 5235, 2018-10-17-

Update of surface albedo database

01.00.02

NRTI: orbit 3745, 2018-07-04
OFFL: orbit 3661, 2018-06-28

Orbit 3946, 2018-07-18
Orbit 3847, 2018-07-11-

Initial operational version

Table 2: History of NO2 processor versions. In orange, the data versions that are no longer available to the users on the Pre-operations hub.

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Product Quality

3.1

Recommendations for data usage

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The quality of the individual observations depends on many factors, including cloud cover, surface
albedo, presence of snow-ice, saturation, geometry etc. These aspects are taken into account in thedefinition of the "quality assurance value" (qa_value), available for each individual observation, which
provides the users of the data with an easy filter to remove less accurate observations. The qa_value
is a continuous variable, ranging from 0 (error) to 1 (all is well). The main flag for data usage is asfollows:
For the variables nitrogendioxide_tropospheric_column,
nitrogendioxide_total_column, nitrogendioxide_summed_total_column:•

qa_value > 0.75
This is the recommended pixel filter. It removes cloud-covered scenes (cloud radiance fraction> 0.5), partially snow/ice covered scenes, errors, and problematic retrievals.

•

qa_value > 0.50
Compared to the stricter filter, this adds the good quality retrievals over clouds and over scenes
covered by snow/ice. Errors and problematic retrievals are still filtered out. In particular, this filter
may be useful for assimilation and model comparison studies.

For variable nitrogendioxide_stratospheric_column:•

qa_value > 0.50

For further details, data users are encouraged to read the Product User Manual (PUM) and Algorithm
Theoretical Basis Document (ATBD) associated with this data product, available on
https://sentinels.copernicus.eu/web/sentinel/technical-guides/sentinel-5p/products-algorithms.

3.2

Validation results

3.2.1

Status of product validation

Independent preliminary validation by S5p MPC Cal/Val experts and the S5PVT concludes that NRTI /OFFL NO2 data is in overall agreement with (i) reference measurements collected from global groundbased networks, (ii) the corresponding satellite data products from OMI, and (iii) is compliant with therequirements as defined in S5p Calibration and Validation Plan [RD01], see Table 1.
The upgrade to version 01.04.00 involved a change (see section 5) of the FRESCO-S auxiliary cloud
product which resulted in an expected substantial increase of the tropospheric NO2 column with respect
to the previous version 01.03.02. The upgrade to version 02.02.00 leads to a further increase of thetropospheric NO 2 columns for polluted cloud-free scenes (see section 5). Exhaustive validation ofversions 01.04.00, 02.02.00, and 02.03.01 was performed by the S5P MPC Cal/Val team since theoperational switches at the beginning of December 2020 and July 2021.
Up to date validation results are available in the ROCVR reports that are accessible through the MPC
VDAF website at http://mpc-vdaf.tropomi.eu. The ROCVR reports are issued quarterly and reports
released after September 2021 include validation results based on processor version 02.xx.xx, while
previous ROCVR reports cover validation results only for versions 01.02.xx up to 01.04.00.

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Data Quality Remarks

4.1

Known Data Quality Issues

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Currently, the following data quality issues are known, not covered by the quality flags, and should be
kept in mind when using the NO2 product.
Bands 4 and 6 spatial misalignment
The band 4 (450 pixels per scanline) footprints, used for the NO 2 DOAS retrieval, are not fully alignedwith the band 6 footprints, used for cloud and scene pressure retrievals. In the worst case, themisalignment can be in the order of half a ground pixel. The misalignment requires interpolation of thecloud and scene pressure, which may introduce additional uncertainty in those parameters. These
parameters are used in the NO2 air-mass factor calculations. Note that the cloud fraction is determinedin the NO2 fitting window, avoiding the uncertainty by misalignment for this parameter.
Surface albedo climatology
The surface albedo climatology up to version 02.03.01 has a spatial resolution of 0.5°x0.5°, which iscoarse compared to the much higher spatial resolution of S5p TROPOMI of 3.5 x 5.5 km. As aconsequence, the albedo grid affects the NO2 column products quality for instance at coastal areas. In
version 02.04.00 the TROPOMI DLER is introduced in the NIR band (cloud retrieval) and NO 2 fit window
around 440 nm. This greatly improves the spatial resolution to 0.125°x0.125°.
Conservative filtering
The pixel flagging, reflected in the qa_value, is defined in a conservative way. When the FRESCO
cloud retrieval reports an error, in combination with the misalignment issue, one consequence is theloss of the first row (west side of the orbit), even though good NO2 slant column retrievals are possible.
Another example is the removal of observations when the albedo database shows suspiciously highvalues.
Variables in the NO2 DOAS fit with an across-track low-order “wave” (since version 02.02.00)
Some variables in the NO2 DOAS fit have an across-track low-order "wave", causing unexpected values
mainly in the western part of the swath. The variables concerned are the slant columns of ozone, liquidwater and O2-O2 in the NO2 fit. The NO2 slant columns are not significantly affected. This indicates theeffect is caused by something that varies smoothly with wavelength and thus may be related to the L1b
degradation correction, i.e.: to the fact that the irradiance is corrected for degradation (since the usageof L1b version 02.00.00, beginning of July 2021, see Table 2) while the radiance is not. The issue may
change once the radiance degradation correction is also in place.

4.2

Solved Data Quality Issues

NRTI data gaps northern hemisphere (solved in version 01.01.00)
The NRTI data stream shows data gaps over Kazakhstan, southern part of Russia and Canada due toa miss-configuration of the processing facility. This issue is solved with the activation of processor
version 01.01.00 on July 2018 (see Table 2).
Orbit numbering in NRTI and OFFL (solved in version 01.02.02)
NRTI orbit numbers are set with respect to the downlink orbit while OFFL orbit numbers are set withrespect to the equator crossing time. This creates an inconsistency between the NRTI and OFFL orbit
numbers. This problem was solved with the activation of processor version 01.02.02 (see Table 2), after
which the orbit numbers are consistent.

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Metadata/Attributes (solved in version 02.02.00)
The spatial resolution of the TROPOMI measurements is improved by bringing the along track groundpixel size from 7.0 to 5.5 km starting on 6th August 2019. Note that, after this operations change, themetadata/Attributes fields related to the spatial resolution, remain unchanged (hence not aligned to theimproved resolution). These fields have been updated with the activation of Level 2 processors version
02.02.00.
Metadata values exchanged (solved in version 02.02.00)
The global attributes geospatial_lon_min and geospatial_lon_max values are exchanged;
therefore, the user is advised to switch the values for these fields, making note that thegeospatial_lat_min and geospatial_lat_max values are correct. This is an issue traceable toL1b data (version 01.00.00) and is corrected since the switch to version 02.00.00 of the Level 1B
processor.
Flagging of Saturation (solved in version 02.02.00)
Some TROPOMI pixels over bright scenes are affected by saturation. Those pixels are flagged and their
quality is reflected in the qa_value. Nevertheless, in the vicinity of saturated pixels there might bepixels also affected by saturation due to the so-called blooming effect. The pixels affected by blooming
effect have been flagged since version 02.00.00 of the Level 1b processor, operational since July 2021.
Wavelength assignment (solved in version 02.02.00)
The selection of the spectral index range that comprises the wavelength window needed for the
wavelength calibration and DOAS retrieval steps has been optimised. The impact is very small, limited
to only about 20 rows, and only visible in the slant column uncertainty.
NRTI Ghost Column (solved in version 02.02.00)
The unit of the ghost column is corrected in the NRTI product.
OFFL metadata (solved in version 02.02.00)
Offline only: metadata fix (in Chemistry Transport Model TM5 loop).
Wavelength window (solved in version 02.03.01)
The window of the wavelength was not correct in version 02.02.00, with negligible effect on the NO2column data. The fit window has been corrected in version 02.03.01: [405, 465] nm.
Wavelength calibration variables not filled in correctly (solved in version 02.03.01)
The wavelength calibration variables were not filled in correctly in version 02.02.00. This has been fixedin version 02.03.01. The variables are:wavelength_calibration_offset, wavelength_calibration_offset_precision,
wavelength_calibration_chi_square,
wavelength_calibration_irradiance_offset,
wavelength_calibration_irradiance_offset_precision,
wavelength_calibration_irradiance_chi_square,polynomial_coefficients, polynomial_coefficients_precision
Geolocation co-added when they should not be (solved in version 02.03.01)
In version 02.02.00, the geolocation of pixels near the pole show a shift of up to 300 meters due to a coaddition activity performed by mistake. This has been corrected in version 02.03.01.
Data in snow_ice_flag variable for pixels with SZA > 88° (solved in version 02.04.00)
The snow_ice_flag value for ground pixels with SZA > 88° is incorrectly set to 255, the NISE flag for“ocean”, rather than the FillValue 254 (the NISE flag for an error). Since ground pixels with SZA > 88°
are not processed, these pixels do not have NO2 column data, hence the NO2 data quality is not affected.

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4.3

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Data Features

This section describes some characteristics of the data that might seem anomalous, however they arephysically correct and not related to any problem.
Pixel geolocation around North Pole (feature)
The solar irradiance is measured on a daily basis over the North Pole at a reference azimuth angle toremove seasonal effects on the measurements. To this end, a yaw manoeuvre is executed when the
instrument is still in radiance mode, causing possible distortion on the scanlines observed during thismanoeuvre (i.e. crossing scanlines, "bow-tie" ground pixel shape instead of rectangular). This occurs at
most during the last 26 seconds of radiance measurements every 15th orbit (once every 25 hours).
Though this may seem anomalous, it is physically correct, and not related to any problem on the data
geolocation.

4.4

Mission Operations Changes

A change in the Copernicus Sentinel 5P operations scenario, increasing the spatial resolution from 7.0
km to 5.5 km along track for all measurements, became operational starting from 6 August 2019, orbit
9388.

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Algorithm Change Record

For a detailed description of the L2__NO2___ algorithms, please refer to the ATBD [RD02].
Important notes for users:•

The upgrade to version 02.02.00 (5 July 2021) leads to an increase of the tropospheric NO 2
columns for cloud-free pixels. The previous upgrade to version 01.04.00 (2 December 2020) led
to a substantial increase of the tropospheric NO2 columns over polluted areas for scenes withsmall cloud fractions. Studies including both data before and after the activation of these
versions will therefore show artificial (positive) jumps.

•

Studies of time series, trend studies or comparisons between years should ideally be based on
consistent datasets, and users are encouraged to use the latest reprocessed (RPRO) dataset
based on version 02.04.00 in combination with the offline version 02.04.00 from 26 July 2022
onwards.

Version 02.05.00
The version 02.05.00 NO2 product implements a small bug fix in the OFFL code. The change only affects
the qa_value field in the datafiles, and only over snow or ice covered regions. In the corrected OFFL
version there are more pixels that receive a qa_value > 0.75, in case the scene pressure over snow/ice
matches the surface pressure to within 4% (was 2% in previous versions). The OFFL 02.04.00 code,
operational since 17 July 2022, did not receive this latest change. This update makes OFFL consistent
with NRTI, RPRO v02.04.00 and the ATBD [RD02].
Version 02.04.00
The version 02.04.00 NO2 product implements one major change compared to version 02.02.00 (or02.03.01). In this version the original OMI and GOME-2 derived surface albedo climatologies in the NO2
fitting window were replaced by a surface albedo climatology derived from TROPOMI observations. This
new TROPOMI surface albedo climatology (Directional Lambertian Equivalent Reflectivity or DLER) is
consistently applied in the FRESCO cloud fraction and cloud pressure retrievals, in the cloud fraction
retrievals in the NO2 window, and in the air-mass factor calculation.
The TROPOMI DLER has several advantages:•

It accounts for the directionality or viewing-angle dependence of the scattering at the surface.
Especially over vegetation in the near infrared this is a strong effect, impacting the FRESCO
cloud retrieval.

•

It improves the spatial resolution of the database from 0.5x0.5 degree to 0.125x0.125 degree,
better resolving the variability.

•

It is representative of more recent years.

•

It shows less remnants of clouds and snow than the previous OMI LER.

The impact was tested for September 2020 and is shown in Figure 1. Over Europe, North America andEast China the averaged difference in the tropospheric column is relatively minor, but especially overvegetated regions like South America or Central Africa the changes are substantial.

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Figure 1: Tropospheric column difference (v02.04.00-v02.03.01) comparing v02.04.00, using
the TROPOMI DLER database, with v02.03.01 using the OMI LER in the NO2 fit window, and
the GOME-2 LER for the FRESCO cloud retrieval in the NIR. Note that 10 15 molec/cm2
corresponds to about 16 μmol/m2. Data is gridded and averaged for September 2020.
Version 02.02.00
The main changes in the upgrade from version 01.04.00 to 02.02.00 are:•

The main change in the NO2 tropospheric column as compared to version 01.04.00 is linked toa different treatment of the surface albedo. In the NO 2 window the surface albedo is now
adjusted to avoid negative cloud fractions while maintaining radiance closure. This leads to asignificant increase (10-15%) of tropospheric NO2 for polluted cloud-free scenes on topof the increase for pixels with a small but non-zero cloud cover in v01.04.00 related to the
FRESCO cloud retrieval upgrade (Figure 2) Similarly, for fully clouded scenes with brightclouds, the cloud albedo is adjusted, rather than allowing cloud fractions > 1. Similar changes
were made before in the FRESCO cloud fraction retrieval.

•

The snow/ice information is now taken from the daily ECMWF meteorological analyses,
replacing the NISE snow-ice flag. This solves the issue that NISE is undetermined aroundcoastlines and improves the resolution and reliability.

•

The results of a newly developed O2-O2 cloud algorithm are integrated (this is similar to the OMI
cloud algorithm using the O2-O2 collision induced absorption around 477 nm). These cloudparameters are retrieved and stored in the output NO 2 product, but not used in the conversion
from NO2 slant column to vertical column (AMF calculations). This is foreseen for futureversions. The regridded FRESCO-wide cloud parameters (see version 01.04.00 upgrade
below) are written to the NO2 product as well, and these parameters are used in the retrieval.

•

The updates of the level-1b (ir)radiance spectra have a relatively small impact on the absolutevalue of the NO2 SCD, SCD error and RMS error of the fit of on average +2%, −1% and −6%,
respectively. The increase of the SCD mainly impacts the stratospheric column.

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Figure 2: Comparison of the NO2
tropospheric VCD of orbit 03704 of 1
July 2018, showing all ground pixels
for which both the v1.2 (x-axis) andv2.1 (y-axis) cloud retrieval gives zerocloud fraction, and for which thesurface albedo may have beenadjusted, and the tropospheric VCD
was found to be positive. The linear fit
coefficient is 1.128, indicating a 13%
increase of the tropospheric NO2column for cloud-free scenes andcolumns up to 300 µmol/m2.

•

The spike removal introduced in version 02.02.00 has a strongly positive impact on pixels which
are not flagged for saturation or blooming in L1b but are, nevertheless, influenced by saturation
effects. Over bright clouds the number of good quality retrievals has increased, of importancee.g., for lightning NOx studies. Furthermore, the spike removal improves the quality of theretrievals over the South Atlantic Anomaly region, with strong reductions of the slant column
noise.

Version 01.04.00
The main changes in the upgrade from version 01.03.02 to 01.04.00 are:•

The FRESCO-S cloud retrieval scheme is updated to span a wider range of wavelengths in the
O2-A band, including the weaker absorption features (FRESCO-wide). As a result, the cloudpressures show an overall decrease, especially for low clouds. For high clouds the changes are
relatively minor. Figure 3 shows the change in cloud pressure for pixels with a qa_value >0.75, which are pixels with a cloud radiance fraction < 0.5, pixels which are mostly cloud-free.
More detailed inspection shows that the updated FRESCO provides more realistic pressures,for instance in the case of heavy aerosol loads or in the case of low clouds over sea/ocean. In
the latter case the previous FRESCO version often shows pressures equal to the sea surfacepressure, but the FRESCO update produces more realistic elevated cloud heights.
As a result of the higher clouds, the air-mass factor is reduced between 0 and 50%, dependingon the location and cloud fraction. For a cloud fraction equal to zero there is no difference (seeFigure 4, left). As a consequence, the tropospheric NO2 column is increased between 0 andabout 50% (see Figure 4, right). Similar results are found over other continents.

•

Because of the overall decrease in cloud pressure, the criterion to decide if pixels above snow
and ice are cloudy or cloud-free was also adjusted. This criterion is based on the difference
between surface and cloud pressure as described in the ATBD [RD02].

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Figure 3: he cloud pressure difference (V01.03.02 using previous FRESCO minus V01.04.00
using the new FRESCO-wide) for 10 May 2019 over East Asia (unit: hPa). Note that the data
has been filtered for qa_value > 0.75, which implies nearly cloud free pixels. For the cloudpressure retrieval this is the most difficult subset of pixels (but also the relevant subset for NO2
retrievals). Over land, the retrieved pressures for these nearly cloud free pixels may differ bymore than 200 hPa for small cloud fractions. The new FRESCO V01.04.00 shows lower cloudpressures in most cases (yellow-red colors). Over sea and ocean, the differences are smaller,
up to 50 hPa. For cloud-covered pixels (not shown) the differences are smaller.

Figure 4: Left: the air-mass factor ratio (V01.03.02/V01.04.00). Right: the NO2 tropospheric column
ratio (V01.04.00/ V01.03.02). White and yellow colours indicate small changes < 15% for most of thedomain, but a substantial fraction of observations, including polluted regions, shows columns
enhanced by up to 50% (red).
Version 01.03.00
The main changes in the upgrade from version 01.02.00 to 01.03.00 are:•

The FRESCO-S cloud retrieval has been updated. The surface albedo is now adjusted to matchthe top-of-atmosphere reflectance if the top-of-atmosphere reflectance is lower than expectedusing the prescribed surface albedo and cloud fraction 0. In this way negative cloud fractions
are avoided. Similar changes were implemented for fully cloud covered scenes (see Figure 5).

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The rules determining the qa_value have been adjusted. In particular the lower limit on the
tropospheric air-mass factor was reduced, which increases the number of valid pixels
somewhat.

•Two
outputfieldswereadded,
the“air_mass_factor_clear”
and“air_mass_factor_cloudy” (see section 6.1.6), which are the tropospheric air-mass factors
for cloud fraction 0 and 1, respectively.

•

The wind speed at 10m altitude was added for interpretation of the observations (direction of
the pollution plumes).

Figure 5: the retrieval of tropospheric NO2 over France on 24 February 2018, for version 01.02.00 (left)
and version 01.03.00 (right). Data has been filtered for clouds (white area). In the (relatively rare) casethat the cloud fraction from the NO 2 spectral window is positive, but FRESCO-S (v01.00-01.02) retrievesa negative cloud fraction with unrealistic cloud pressures, this was resulting in high, noisy NO 2 spots
around Paris (left panel, v01.00-01.02). With the new treatment in FRESCO-S, resulting in more realistic
cloud pressures, these spots disappear and we observe a well-defined pollution plume from Paristransported by the wind from the north-east (right panel, v01.03).
Version 01.02.00
The main changes in the upgrade from version 01.01.00 to 01.02.00 can be summarized as follows:•

A "destriping" algorithm is used to remove across-track biases between the individual viewing
angles. A stripe amplitude is computed on a daily basis over the (clean) tropical Pacific Ocean,
averaged over a 30-degree latitude region and over a period of 7 days. The array of stripe
amplitudes is provided in the L2 files and also in the product support file (see 6).

•

The retrieval for the high Solar Zenith Angles (SZA) and polar regions has improved throughseveral changes. In the TM5-MP model, the photolysis for SZA > 85º was improved, impacting
in particular the stratospheric NO2 columns at high latitudes. The assimilation of NO 2
observations is now restricted to the ascending part of the orbit (see Figure 7).

•

Good quality retrievals over snow-ice now receive a qa_value > 0.75 when the scene pressure
from the FRESCO-S cloud retrieval is close to the surface pressure. The cloud retrieval cannot
distinguish clouds from snow/ice, but the near equivalence of the scene pressure and surfacepressure indicates that the scene is (nearly) cloud-free. Together with the high SZA
improvements, the number of reliable retrievals over high latitude regions has increased
substantially.

•

The computation of the thermal tropopause level now uses a more advanced algorithm,
resulting in a more realistic distribution of tropopause pressures.

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Figure 6: A comparison of the mean total column (stratosphere plus troposphere) averaged
over the tropical Pacific on 15 July 2018 as a function of the viewing angle, or row index.
The red curve is the v1.1.0 results without destriping, and the blue curve is the v1.2.0 resultwith the destriping (the stripe correction is averaged over a week). In black we show a 50row running mean of the blue curve. The red curve shows single-row spikes, as well as
correlated structures, such as the high values around row 200 and the low values around40, 320 or 420. The plot shows that the stripe filtering removes the major part of both thehigh and low frequency variability. Note that the amplitude of the structures in the red curveis small, generally within 5% of the column over the clean Pacific Ocean. Also note that we
expect an increase of the total column in the stratosphere from left to right, as indicated by
the black curve, due to the diurnal cycle of stratospheric NOx chemistry.

Figure 7: The NO2 tropospheric column retrievals for the descending part of orbit 3623, 25 June 2018,19 UTC, over Siberia. Version 1.0.2 is shown on the left and version 1.2.0 on the right. Prominent
unrealistic positive biases are observed in v1.0.2 (as it also occurs in v1.1.0) for the highest solar
zenith angles on the left side of the orbit, while v1.2.0 has much more realistic values close to zerowith a tendency towards a weak negative bias.

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Data Format

The product is stored as NetCDF4 file. The NetCDF4 file contains both the data and the metadata forthe product.
For OFFL data the product is stored as a single file per satellite orbit, for NRTI data the product is stored
as multiple files (5 minute granules) per orbit.
Please note that consecutive data granules of the NRTI product show an overlap of about 12 scan lines.
Details of the data format are provided in the Product User Manual (PUM) [RD03].

6.1

Data format changes

6.1.1

Version 02.05.00

Attribute fields with text changes
In variable /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/wavelength_calibration_offset
attribute ‘long_name’ → text changed (from ‘wavelength offset’ to ‘radiance wavelength offset’)In variable /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/wavelength_calibration_offset_precisionattribute ‘long_name’ → text changed (from ‘wavelength offset precision’ to ‘radiance wavelength offset
precision’In variable /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/wavelength_calibration_stretch
attribute ‘long_name’ → text changed (from ‘wavelength stretch’ to ‘radiance wavelength stretch’)In variable /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/wavelength_calibration_stretch_precisionattribute ‘long_name’ → text changed (from ‘wavelength stretch precision’ to ‘radiance wavelength stretch precision’)In variable /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/wavelength_calibration_chi_square
attribute ‘long_name’ → text changed (from ‘wavelength calibration chi square’ to ‘radiance wavelength
calibration chi square’)In variable /PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/wavelength_calibration_irradiance_chi_square
attribute ‘long_name’ → text changed (from ‘wavelength calibration irradiance chi squared’ to ‘irradiancewavelength calibration chi squared’)
6.1.2

Version 02.04.00

New fields added/METADATA/QA_STATISTICS/number_of_thermal_instability_warning_occurrences
In variable:/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/processing_quality_flags
Added element to attribute ‘flag_meanings’: [success, radiance_missing,irradiance_missing, input_spectrum_missing, …, thermal_instability_warning]
Added element to attribute ‘flag_masks’: [255, 255, 255, …, 1073741824]
Added element to attribute ‘flag_values’: [0, 1, 2, 3, 4, …, 1073741824]
6.1.3

Version 02.03.01

New fields added/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/
o22cld_wavelength_calibration_irradiance_offset_precision
Removed fields/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_cloud_fraction_crb_not_clipped/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_cloud_pressure_crb_not_clipped

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Renamed fields/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/wavelength_calibration_irradiance_offset
attribute ‘long_name’ → text changed (from ‘wavelength offset’ to ‘irradiance wavelength offset’/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/wavelength_calibration_irradiance_offset
attribute ‘ancillary_variables’ → text changed (from ‘wavelength_calibration_offset_precision’ to‘wavelength_calibration_irradiance_offset_precision’
6.1.4

Version 02.02.00

New fields added/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/cloud_selection_flag (The configuration of version
2.2.0 fixes this to FRESCO)/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_cloud_fraction_crb/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_cloud_fraction_crb_not_clipped/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_cloud_fraction_crb_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_cloud_pressure_crb/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_cloud_pressure_crb_not_clipped/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_cloud_pressure_crb_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_cloud_height_crb/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_cloud_height_crb_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_cloud_albedo_crb/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_scene_albedo/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_scene_albedo_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_apparent_scene_pressure/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_apparent_scene_pressure_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_chi_square/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_continuum_at_reference_wavelength/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_continuum_at_reference_wavelength_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_polynomial_coefficient/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_polynomial_coefficient_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_ring_coefficient/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_ring_coefficient_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_nitrogendioxide_slant_column_density/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_nitrogendioxide_slant_column_density_precision

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Page 19 of 23/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_oxygen_oxygen_dimer_slant_column_density/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_oxygen_oxygen_dimer_slant_column_density_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_oxygen_oxygen_dimer_slant_column_density_correction_factor/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_ozone_slant_column_density/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_ozone_slant_column_density_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_surface_albedo/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_wavelength_calibration_irradiance_offset/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_wavelength_calibration_offset/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_wavelength_calibration_offset_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_wavelength_calibration_stretch/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/O22CLD/o22cld_wavelength_calibration_stretch_precision/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/FRESCO/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/FRESCO/fresco_cloud_fraction_crb/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/FRESCO/fresco_cloud_pressure_crb/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/FRESCO/fresco_scene_albedo/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/FRESCO/fresco_apparent_scene_pressure/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/FRESCO/fresco_cloud_albedo_crb/PRODUCT/SUPPORT_DATA/DETAILED_RESULTS/FRESCO/fresco_surface_albedo/PRODUCT/SUPPORT_DATA/INPUT_DATA/surface_albedo attribute ancillary_variables/PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_pressure_crb attribute ancillary_variables/PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_fraction_crb attribute ancillary_variables/PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_albedo_crb attribute ancillary_variables/PRODUCT/SUPPORT_DATA/INPUT_DATA/scene_albedo attribute ancillary_variables/PRODUCT/SUPPORT_DATA/INPUT_DATA/apparent_scene_pressure attributeancillary_variables/METADATA/QA_STATISTICS attribute number_of_missing_scanlines/METADATA/QA_STATISTICS attribute
number_of_max_num_outlier_exceeded_error_occurrences/METADATA/GRANULE_DESCRIPTION attribute CollectionIdentifier
Removed fields/METADATA/ISO_METADATA/gmd:identificationInfo/gmd:spatialResolution/PRODUCT/SUPPORT_DATA/INPUT_DATA/surface_albedo_nitrogendioxide_window
attribute radiation_wavelength (removed by mistake, will be added at the first opportunity)

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Page 20 of 23/PRODUCT/SUPPORT_DATA/INPUT_DATA/surface_albedo attribute radiation_wavelength/PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_pressure_crb attribute source/PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_fraction_crb attribute source/PRODUCT/SUPPORT_DATA/INPUT_DATA/cloud_albedo_crb attribute source/PRODUCT/SUPPORT_DATA/INPUT_DATA/scene_albedo attribute source/PRODUCT/SUPPORT_DATA/INPUT_DATA/scene_albedo attribute radiation_wavelength/PRODUCT/SUPPORT_DATA/INPUT_DATA/apparent_scene_pressure attribute source
Renamed fields/PRODUCT/qa_value attribute valid_min_ → /PRODUCT/qa_value attribute valid_min/PRODUCT/qa_value attribute valid_max_ → /PRODUCT/qa_value attribute valid_max/METADATA/QA_STATISTICS attribute number_of_aai_warning_occurrences→ /METADATA/QA_STATISTICS attribute number_of_AAI_warning_occurrences
6.1.5

Version 01.04.00

There are no format changes with respect to the previous version.

6.1.6

Version 01.03.00

New fields added/PRODUCT_SUPPORT_DATA/DETAILED_RESULTS/air_mass_factor_clear/PRODUCT_SUPPORT_DATA/DETAILED_RESULTS/air_mass_factor_cloudy/PRODUCT/SUPPORT_DATA/INPUT_DATA/eastward_wind/PRODUCT/SUPPORT_DATA/INPUT_DATA/northward_wind
6.1.7

Version 01.02.00

New variables/PRODUCT_SUPPORT_DATA/DETAILED_RESULTS/nitrogendioxide_slant_column_density_stripe_amplitude (added also to the auxiliary input CTMFCT files)

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Product Availability

The data are available from the Copernicus Open Data Hub https://scihub.copernicus.eu.
Also, the full mission reprocessed products can be found on the mentioned Open Access Hub and canbe identified by the file class ‘RPRO’ in the filenames. The collection identifier is ‘03’, the same used forthe operational dataset that is available since mid-July 2022 (all with version 2.4.0).
The list of major mission data gaps due to acquisition faults or satellite/instrument disruption is available
at https://sentinel.esa.int/web/sentinel/missions/sentinel-5p/mission-status. For those periods the data
are permanently lost.
RPRO dataset gaps: additional gaps are present on the reprocessed dataset (see Table 3) due to theunavailability of Level 0 (L0) input data during the full mission reprocessing campaign.

Orbit

Gap start time

Gap stop time3546

20/06/2018 08:31:35

20/06/2018 08:51:37

9755
10782
19782
19785
20254

31/08/2019 23:46:24

01/09/2019 00:06:25

12/11/2019 08:39:57

12/11/2019 09:29:55

07/08/2021 18:09:52

07/08/2021 18:27:54

07/08/2021 22:34:02

07/08/2021 22:50:52

10/09/2021 00:01:42

10/09/2021 00:21:43

Table 3: Gaps on RPRO dataset due to the unavailability of L0 input
data during the full mission reprocessing campaign
Information on data handling tools is available from the web page http://www.tropomi.eu/tools.
For further questions regarding S5P/TROPOMI data products please contact
EOSupport@Copernicus.esa.int.
The access and use of any Copernicus Sentinel data available through the Sentinel Data Hub isgoverned by the Legal Notice on the use of Copernicus Sentinel Data and Service Information and isgiven here:
https://sentinels.copernicus.eu/documents/247904/690755/Sentinel_Data_Legal_Notice.

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References[RD01]

Sentinel-5 Precursor Calibration and Validation Plan for the Operational Phase
source: ESA; ref: ESA-EOPG-CSCOP-PL-0073;
url: https://sentinels.copernicus.eu/documents/247904/2474724/Sentinel-5PCalibration-and-Validation-Plan.pdf[RD02]

Sentinel-5 precursor/TROPOMI Level 2 Algorithm Theoretical Basis Document Total
and Tropospheric NO2 Data Products,
source: KNMI; ref: S5P-KNMI-L2-0005-RP;
url: https://sentinels.copernicus.eu/documents/247904/2476257/Sentinel-5PTROPOMI-ATBD-NO2-data-products[RD03]

Sentinel-5 precursor/TROPOMI Level 2 Product User Manual Nitrogen Dioxide
source: KNMI; ref: S5P-KNMI-L2-0021-MA;
url: https://sentinels.copernicus.eu/documents/247904/2474726/Sentinel-5P-Level-2Product-User-Manual-Nitrogen-Dioxide[RD04]

Validation Reports of the Sentinel-5 Precursor Operational Data Products
Source: BIRA; ref: S5P-MPC-IASB-ROCVR;
url: http://mpc-vdaf.tropomi.eu/[RD05]

Algorithm theoretical basis document for the TROPOMI L01b data processor
source: KNMI; ref: S5P-KNMI-L01B-0009-SD;
url: https://sentinels.copernicus.eu/documents/247904/2476257/Sentinel-5PTROPOMI-Level-1B-ATBD

More information on this data product is available from the Copernicus Sentinel product webpage:https://sentinels.copernicus.eu/web/sentinel/technical-guides/sentinel-5p/products-algorithms,
and from the corresponding TROPOMI product webpage http://www.tropomi.eu/data-products.

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Abbreviations and acronyms
AO

Announce of Opportunities

ATBD

Algorithm Theoretical Basis Document

BIRA-IASBRoyal Belgian Institute for Space Aeronomy

DLER

Directional Lambertian Equivalent Reflectivity

DLR

German Aerospace Center / Deutsches Zentrum für Luft- und Raumfahrt

DOAS

Differential Optical Absorption Spectroscopy

DOI

Digital Object Identifier

ECCC

Environment and Climate Change Canada

ESA

European Space Agency

ESL

Expert Support Laboratory

ESRIN

European Space Research Institute of ESA

FMI

Finnish Meteorological Institute

IUPB

University of Bremen

FRESCO

Fast REtrieval Scheme for Clouds from the Oxygen A band

KNMI

Koninklijk Nederlands Meteorologisch Instituut – Royal Dutch Meteorological Institute

LATMOS-CNRS

Laboratoire Atmosphères, Observations Spaciales - Centre National de la Recherche
Scientifique

MAX-DOAS

Multi Axis Differential Optical Absorption Spectroscopy

MPC

Mission Performance Centre

MPI-Mainz

Max Planck Institut, in Mainz

NASA

National Aeronautics and Space Administration

NRT

Near-Real Time

NRTI

Near-Real TIme (data product)

OFFL

Off-line (non-time-critical data product)

OMI

Ozone Monitoring Instrument

PRF

Product Readme File

PUM

Product User Manual

QDOAS

Cross-platform application for DOAS retrievals, developed by BIRA-IASB

QWG

Quality Working GroupROCVR

Routine Operations Consolidated Validation Reports

RPRO

Retrieval reprocessing product

S5P

Sentinel-5 Precursor

S5PVT

Sentinel-5 Precursor Validation TeamTROPOMITROPOspheric Monitoring Instrument

VCD

Vertical Column Density

VDAF

Validation Data Analysis Facility