![](media/image1.png){width="6.666666666666667in"
height="2.232638888888889in"}

**Users Manual for the Group for High Resolution Sea Surface Temperature
(GHRSST-PP)**

**Draft V1.2**

**Revision schedule**

  ---------------- --------------------------------------------------------
  **Reference:**   GHRSST/17

  **Issue:**       Users Manual V0.1

  **Date of        Thursday,March 27, 2008
  issue:**         

  **Document       Reference document
  type:**          

  **Authors:**     The GHRSST Science Team

  **Revision       March 27, 2008 Jorge Vazquez
  History:**       

  **Version 0.8**  April 21,2008 Jorge Vazquez

  **Version 1.0**  May 3. 2008 Jorge Vazquez, Chelle Gentemann, Helen Beggs

  **Version 1.2**  July 17, 2008 Jorge Vazquez
  ---------------- --------------------------------------------------------

1\. General Introduction [4](#general-introduction)

2.0 Description of Data [4](#description-of-data)

2.1 SST Processing Levels and Overview
[4](#sst-processing-levels-and-overview)

2.2 Where do I get data from? [5](#where-do-i-get-data-from)

2.3 Data Format and how do I read the data?
[6](#data-format-and-how-do-i-read-the-data)

2.3.1 netCDF [6](#netcdf)

2.3.2 How to read SST and confidence flags
[6](#how-to-read-sst-and-confidence-flags)

2.3.3 How do I decide what product to use?
[7](#how-do-i-decide-what-product-to-use)

2.3.4 What software can I use to read the data
[10](#what-software-can-i-use-to-read-the-data)

2.4 Complete GHRSST Data Formats [10](#complete-ghrsst-data-formats)

2.4.1 Level 2 Preprocessed (L2P) [10](#level-2-preprocessed-l2p)

2.4.2 Level 4 Analyzed Fields [17](#level-4-analyzed-fields)

2.4.3 GDSV2.0 L2, L3, and L4 File Naming Conventions
[20](#gdsv2.0-l2-l3-and-l4-file-naming-conventions)

3\. 0 Methods for Accessing Data [21](#methods-for-accessing-data)

3.1 OPenDAP [21](#opendap)

3.2 FTP [21](#ftp)

3.3 HTTP [21](#http)

3.4 POET [21](#poet)

4.0 Using Data (Confidence Flags and Ancillary Fields)
[23](#using-data-confidence-flags-and-ancillary-fields)

4.1 Description of how to use confidence flags and/or quality levels
[23](#description-of-how-to-use-confidence-flags-andor-quality-levels)

4.1.2 MICROWAVE [23](#microwave)

4.1.3 MSG/SEVIRI SST [23](#msgseviri-sst)

4.2 Confidence levels and SSES [24](#confidence-levels-and-sses)

4.3 Description of Ancillary Fields
[24](#description-of-ancillary-fields)

5.0 Frequently Asked Questions [24](#frequently-asked-questions)

6.0 Getting information on GHRSST [24](#getting-information-on-ghrsst)

6.1 Google [24](#google)

6.2 Wikipedia [25](#wikipedia)

6.3 Peer reviewed publications [25](#peer-reviewed-publications)

6.4 Web of Science and Knowledge [25](#web-of-science-and-knowledge)

6.5 User Contact Information [25](#user-contact-information)

6.5.1 Jet Propulsion Laboratory [25](#jet-propulsion-laboratory)

6.5.2 Bluelink [25](#bluelink)

6.5.3 Long Term Stewardship and Reanalysis Facility (LTSRF)
[25](#long-term-stewardship-and-reanalysis-facility-ltsrf)

7.0 APPENDICES [26](#appendices)

7.1 Example read software in IDL [26](#example-read-software-in-idl)

7.2 The GHRSST Match-Up Database [36](#the-ghrsst-match-up-database)

7.2.1 Overview [36](#overview)

7.2.2 Future plans [36](#future-plans)

7.3 High Resolution Diagnostic Data Sets (HRDDS)
[37](#high-resolution-diagnostic-data-sets-hrdds)

7.3.1 Overview [37](#overview-1)

7.3.2 The HR-DDS portal [37](#the-hr-dds-portal)

7.3.3 Time series analysis [38](#time-series-analysis)

7.3.4 CSV (comma separated value) pages
[40](#csv-comma-separated-value-pages)

7.3.5 FTP and OPeNDAP access [40](#ftp-and-opendap-access)

7.3.6 Multivariate scatter plots [40](#multivariate-scatter-plots)

7.3.7 Quick look image [41](#quick-look-image)

7.3.8 Spatial comparison page [42](#spatial-comparison-page)

7.3.9 Anomaly analysis page [43](#anomaly-analysis-page)

7.3.10 Registered user services [44](#registered-user-services)

7.3.11 MyDDSettes [45](#myddsettes)

7.3.12 Reporting bugs and suggesting changes
[45](#reporting-bugs-and-suggesting-changes)

7.3.13 Accessibility options [45](#accessibility-options)

7.3.14 HR-DDS file format [45](#hr-dds-file-format)

7.3.15 HR-DDS file name convention [46](#hr-dds-file-name-convention)

7.3.16 FAQ [46](#faq)

8.0 SST definitions [46](#sst-definitions)

9.0 RDACs, GDAC, and the LTSRF [49](#rdacs-gdac-and-the-ltsrf)

9\. 1 RDACs [49](#rdacs)

9\. 2 GDAC [49](#gdac)

9\. 3 LTSRF [49](#ltsrf)

10.0 netCDF Structure [50](#netcdf-structure)

10.1 Why use netCDF? [50](#why-use-netcdf)

10.2 NetCDF and CF conventions [51](#netcdf-and-cf-conventions)

10.3 What\'s in a netCDF file? [51](#whats-in-a-netcdf-file)

10.4 Reading and writing netCDF [52](#reading-and-writing-netcdf)

10.5 netCDF resources [52](#netcdf-resources)

11.0 MMR (Master Metadata Repository and search capability)
[52](#mmr-master-metadata-repository-and-search-capability)

#   {#section .unnumbered}

# 1. General Introduction 

The Global Ocean Data Assimilation Experiment (GODAE) is an
international collaboration for ocean forecasting activities, which in
2002 initiated a GODAE High Resolution SST Pilot Project (GHRSST-PP) to
address an emerging need for accurate high-resolution sea surface
temperature (SST) products derived from satellite data. High quality SST
data is required by operational ocean and atmospheric forecasting
systems to constrain the modelled upper ocean circulation thermal
structure and for studies of the exchange of energy between the ocean
and atmosphere. However, individual satellites and their sensors are
individually unable to provide global, high resolution coverage of the
surface temperature of the world's oceans, due to differing satellite
orbits and sensor types.

The primary aim of the Global Ocean Data Assimilation Experiment (GODAE)
High Resolution Sea Surface Temperature Pilot Project (GHRSST-PP) is to
develop and operate an operational demonstration system that will
deliver high-resolution (better than 10 km and \~6 hours), global
coverage, SST data products for the diverse needs of GODAE and the wider
scientific community. A new generation of SST data products is being
derived and served to the user community by combining complementary
satellite and *in situ* SST observations in near real-time.
Significantly, GHRSST SST data products are global in scope, combining
data received from multiple sensors and multiple satellite platforms. A
full description of the GHRSST-PP project is given in the GHRSST-PP
Development and Implementation Plan (GDIP) which can be obtained from
the GHRSST-PP project web server located at
[http://www.ghrsst-pp.org](http://www.ghrsst-pp.org/). For more details
on how SST is defined within the GHRSST project see Appendix 9.5.

The rest of the Users Manual is organized such that detailed information
can be found in the appendices.

# 2.0 Description of Data 

## 2.1 SST Processing Levels and Overview

**L2P data (Level 2 preprocessed data):** - Geophysical variables
derived from orbital source data at the same resolution and location as
the source data (i.e., satellite projection with geographic
information.). Note that "L2" data may be spatially and temporally
irregular, and further processing of the data is required to output data
that is equally spaced temporally and spatially on a grid. (Reference:
<http://goliath.ecnext.com/coms2/summary_0199-1538021_ITM>) Each SST
data file is then reformatted to a common GDS pre-processed data format
referred to in the GHRSST program as L2P (described in Appendix A1). All
GHRSST L2P data is in the netCDF format.

Each L2P data product contains original SST measurements together with
confidence fields and an error estimate (called single sensor error
statistics (SSES)). L2P data products consist of the original SST
measurements (that are not re-gridded or modified) together with
additional confidence and error estimates. A separate L2P data product
is produced for each sensor at each RDAC.

Each input SST data file is assessed pixel by pixel, using gross error
checking rules. A configuration file is used to store all QC parameter
limits and thresholds that will be revised as required. Confidence data
are extracted from native SST data streams if present and they are
derived using auxiliary and reference data streams and sensor specific
error statistics.

Sensor Specific Error Statistics (SSES) are assigned to each SST
measurement based on Several different methodologies.

(a) GHRSST-PP L2P data products will serve the requirements of some
    operational ocean modelling groups in real-time. However, many user
    applications and operational modelling groups request complete SST
    fields, free of gaps caused by clouds, rain or lack of data
    coverage, at regular intervals of between 6 and 24 hours. To address
    these needs, a number of interplated SST products are also
    available.

**L3 data (Level 3 data):**-- L3 data is L2 data that receives further
processing and is equally mapped (gridded) to a projection of the Earth
at various resolutions. Within GHRSST, Level 2 data are mapped on
uniform space-time grid scales (Level 3).

**L4P data:**Each L4 data product is formatted to a common GDS L4 data
format (Appendix A1) that contains the analysis at each grid cell
together with quality control and error statistic information. L4 data
products are available in real-time to the GHRSST-PP user community.
Results from analyses of lower level data (variables derived from
multiple measurements). E.g., SST data sets generated from
multiple-source satellite data using optimal interpolation. GHRSST L4
data are uniform, global, gap-free, high resolution SST products
generated from multiple sensors and multiple satellites through the GDC
process as described below:

There is currently no consensus within the GHRSST-PP science Team or
indeed the international SST community that defines the optimal analysis
procedure to use for the generation of high resolution SST data products
based on multiple satellite data inputs. There are several schemes that
have been developed by operational agencies and research establishments
(e.g., Reynolds and Smith) that could be used but in each case, the
specific method must be adapted to the high resolution space scales that
the GHRSST-PP is attempting to resolve. Significant developments have
already produced viable results at the Japanese RDAC through the New
Generation (NGSST) SST project and further developments are expected
from other approaches at the EU RDAC (within the Medspiration project)
and USA RDAC/GDAC (within the NOPP SST for GODAE project) in the next 12
months. A major goad of he project was to ensure that all GHRSST-PP data
be in the same format. The standard chosen for the GHRSST-PP was netCDF.

## 2.2 Where do I get data from?

Near Real Users (NRT) users should acquire their data from the Global
Data Analysis Centers (GDAC) (http://ghrsst.jpl.nasa.gov) where data are
integrated, catalogued, and served to users for 30 days. Users needing
the full data set should get data from the Long Term Stewardship and
Reanalysis Facility (LTSRF)
([[http://data.nodc.noaa.gov/cgi-bin/nph-dods/ghrsst/]{.underline}](http://data.nodc.noaa.gov/cgi-bin/nph-dods/ghrsst/)),
where they are archived, documented, and served in perpetuity. For more
details on the relationships between the Regional Data Assembly Centers
(RDACs), the GDAC, and the LTSRF see Appendix 9.6.

## 2.3 Data Format and how do I read the data?

### 2.3.1 netCDF

All GHRSST data are stored at netCDF data files that provide a
convenient, standard, self-describing, platform independent format for
data transport. NetCDF (network Common Data Form) is an interface for
array-oriented data access and a freely-distributed collection of
software libraries that provide implementations of the interface. The
netCDF software was developed by Glenn Davis, Russ Rew, Steve Emmerson,
John Caron, and Harvey Davies at the UNIDATA Program Center in Boulder,
Colorado, and augmented by contributions from other netCDF users. The
netCDF libraries define a machine-independent format for representing
scientific data. Together, the interface, libraries, and format support
the creation, access, and sharing of scientific data. The British
Atmospheric Data Centre (BADC) carries *A* *short introduction to netCDF
data.* that provides an excellent introduction to netCDF at
<http://badc.nerc.ac.uk/help/formats/netcdf/index_cf.html>. The complete
netCDF documentation can be found at the UNIDATA web site
<http://www.unidata.ucar.edu/packages/netcdf/index.html>. For more
detailed information see appendix.

###  2.3.2 How to read SST and confidence flags

In most cases users will simply want to read the SST value and apply the
appropriate confidence flag. Confidence flags of 4-5 should be applied
to extract the highest quality data. Additionally a scale and offset
needs to be applied to the SST integer value to convert to degrees
Kelvin. The scale and offset and confidence flags can be directly read
from the netCDF file. Scale_factor and add_offset can be read directly
from the netCDF file. Confidence flags can be read using the
confidence_flag parameter in the netCDF file. To convert to SST then:

SST=sst\*scale_factor+add_offset where SST is in degrees Kelvin.

The following table shows a summary of the netCDF attributes for the
error characteristics, scale factor, offset, and confidence flags. For
more detail and a complete list of all the L2P atrributes, including
time information, see the read software in appendix ?

#### 2.3.2.1 L2P data

Attribute Name Description

  ----------------------------------- -----------------------------------
  sst                                 Sea Surface Temperature as an
                                      integer

  scale_factor                        sst needs to be multiplied by this
                                      factor

  add_offset                          Needs to be added to
                                      sst\*scale_factor

  confidence_flags                    Flag between 0-5 indicating the
                                      quality of the SST pixel. For
                                      highest quality choose 4-5

  SSES_standard_deviation_error       Standard deviation difference
                                      between the satellite SST value and
                                      in-situ data

  SSES_bias_error                     Mean difference between satellite
                                      SST value and in-situ data.
  ----------------------------------- -----------------------------------

#### 

#### 2.3.2.2 L4 data

  ----------------------------------- -----------------------------------
  analysed_sst                        Merged SST from different satellite
                                      sensors

  analysis_error                      Error estimates as result of
                                      optimal estmation.
  ----------------------------------- -----------------------------------

### 2.3.3 How do I decide what product to use?

The GHRSST project makes available several L2P and L4 products. The
following table lists, as of July 16, 2008 all the current products
currently available through the GHRSST project. The table includes
temporal coverage, spatial coverage, temporal resolution and spatial
resolution to facilitate the users deciding what product best suits
their needs.

+-----------------------------------------------------------------------+
| **Product**                                                           |
|                                                                       |
| <table style="width:100%;">                                           |
| <colgroup>                                                            |
| <col style="width: 12%" />                                            |
| <col style="width: 10%" />                                            |
| <col style="width: 11%" />                                            |
| <col style="width: 13%" />                                            |
| <col style="width: 9%" />                                             |
| <col style="width: 9%" />                                             |
| <col style="width: 8%" />                                             |
| <col style="width: 2%" />                                             |
| <col style="width: 0%" />                                             |
| <col style="width: 7%" />                                             |
| <col style="width: 8%" />                                             |
| <col style="width: 7%" />                                             |
| </colgroup>                                                           |
| <tbody>                                                               |
| <tr class="odd">                                                      |
| <td><p><strong> </strong></p>                                         |
| <p><strong>[GHRSST product code]</strong></p></td>                    |
| <td><p><strong>Instrument</strong></p>                                |
| <p><strong>/ Type</strong></p></td>                                   |
| <td><strong>Satellite / Orbit</strong></td>                           |
| <td><strong>Data Source Agency</strong></td>                          |
| <td><strong>Data producer [RDAC code]</strong></td>                   |
| <td><blockquote>                                                      |
| <p><strong>Resolut-ion</strong></p>                                   |
| </blockquote></td>                                                    |
| <td><p><strong>Latitude</strong></p>                                  |
| <p><strong>range</strong></p></td>                                    |
| <td colspan="3"><p><strong>Longitude</strong></p>                     |
| <p><strong>range</strong></p></td>                                    |
| <td><strong>Files per day</strong></td>                               |
| <td><strong>Time Series</strong></td>                                 |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td colspan="12"><strong>L2P</strong></td>                            |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td><p>ATS_NR_2P</p>                                                  |
| <p> </p></td>                                                         |
| <td><p>AATSR</p>                                                      |
| <p>/ Infrared</p>                                                     |
| <p> </p></td>                                                         |
| <td>Envisat / Polar</td>                                              |
| <td>ESA</td>                                                          |
| <td>EUR</td>                                                          |
| <td> 1 km</td>                                                        |
| <td>90ºN -90ºS</td>                                                   |
| <td colspan="3">180ºW - 180ºE</td>                                    |
| <td>15</td>                                                           |
| <td>Mar 2005 -present</td>                                            |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td><p>SEVIRI_SST</p>                                                 |
| <p> </p></td>                                                         |
| <td><p>SEVIRI</p>                                                     |
| <p>/ Infrared</p>                                                     |
| <p> </p></td>                                                         |
| <td>MSG / Geostationary</td>                                          |
| <td>EUMETSAT</td>                                                     |
| <td>EUR</td>                                                          |
| <td>0.1 deg</td>                                                      |
| <td>60ºN -60ºS</td>                                                   |
| <td colspan="3">100ºW - 45ºE</td>                                     |
| <td><p>8</p>                                                          |
| <p>(1 file per 3 hours)</p></td>                                      |
| <td>Feb 2005 -present</td>                                            |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>AMSRE</td>                                                        |
| <td>AMSRE / Microwave</td>                                            |
| <td>Aqua / Polar</td>                                                 |
| <td>Remote Sensing Systems, Inc.</td>                                 |
| <td>EUR</td>                                                          |
| <td>25 km</td>                                                        |
| <td>90ºN -90ºS</td>                                                   |
| <td colspan="3">180ºW - 180ºE</td>                                    |
| <td>14</td>                                                           |
| <td>Feb 2005 – Feb 2007</td>                                          |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>AMSRE</td>                                                        |
| <td>AMSRE / Microwave</td>                                            |
| <td>Aqua / Polar</td>                                                 |
| <td>Remote Sensing Systems, Inc.</td>                                 |
| <td>REMSS</td>                                                        |
| <td>25 km</td>                                                        |
| <td>90ºN -90ºS</td>                                                   |
| <td colspan="3">180ºW - 180ºE</td>                                    |
| <td><p>14</p>                                                         |
| <p>(&amp; 14 realtime  files) *</p></td>                              |
| <td>June 2002 -present</td>                                           |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>AVHRR16_G</td>                                                    |
| <td>AVHRR / Infrared</td>                                             |
| <td>NOAA-16 / Polar</td>                                              |
| <td>NAVOCEANO</td>                                                    |
| <td>EUR</td>                                                          |
| <td>8.8 km</td>                                                       |
| <td>90ºN -90ºS</td>                                                   |
| <td colspan="3">180ºW - 180ºE</td>                                    |
| <td>14</td>                                                           |
| <td>Feb 2005 – Aug 2006</td>                                          |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>AVHRR16_L</td>                                                    |
| <td>AVHRR / Infrared</td>                                             |
| <td>NOAA-16 / Polar</td>                                              |
| <td>NAVOCEANO</td>                                                    |
| <td>EUR</td>                                                          |
| <td>2.2 km</td>                                                       |
| <td colspan="2">90ºN -70ºS</td>                                       |
| <td colspan="2">100ºW - 45ºE</td>                                     |
| <td>1-5</td>                                                          |
| <td>Feb 2005 – Oct 2005</td>                                          |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>AVHRR17_G</td>                                                    |
| <td>AVHRR / Infrared</td>                                             |
| <td>NOAA-17 / Polar</td>                                              |
| <td>NAVOCEANO</td>                                                    |
| <td>EUR</td>                                                          |
| <td>8.8 km</td>                                                       |
| <td>90ºN -90ºS</td>                                                   |
| <td colspan="3">180ºW - 180ºE</td>                                    |
| <td>14</td>                                                           |
| <td>Feb 2005 – Feb 2007</td>                                          |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>AVHRR17_L</td>                                                    |
| <td>AVHRR / Infrared</td>                                             |
| <td>NOAA-17 / Polar</td>                                              |
| <td>NAVOCEANO</td>                                                    |
| <td>EUR</td>                                                          |
| <td>2.2 km</td>                                                       |
| <td>90ºN -70ºS</td>                                                   |
| <td colspan="3">100ºW - 45ºE</td>                                     |
| <td>~1-5</td>                                                         |
| <td>Feb 2005 – Feb 2007</td>                                          |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>AVHRR17_G</td>                                                    |
| <td>AVHRR / Infrared</td>                                             |
| <td>NOAA-17 / Polar</td>                                              |
| <td>NAVOCEANO</td>                                                    |
| <td>NAVO</td>                                                         |
| <td>8.8 km</td>                                                       |
| <td>90ºN -90ºS</td>                                                   |
| <td colspan="3">180ºW - 180ºE</td>                                    |
| <td>14</td>                                                           |
| <td>Jun 2006 – present</td>                                           |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>AVHRR17_L</td>                                                    |
| <td><p>AVHRR /</p>                                                    |
| <p>Infrared</p></td>                                                  |
| <td>NOAA-17 / Polar</td>                                              |
| <td>NAVOCEANO</td>                                                    |
| <td>NAVO</td>                                                         |
| <td>2.2 km</td>                                                       |
| <td colspan="4">N America west and east coasts and various            |
| other</td>                                                            |
| <td>~30</td>                                                          |
| <td><p>Jun</p>                                                        |
| <p>2006 – present</p></td>                                            |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td></td>                                                             |
| <td></td>                                                             |
| <td></td>                                                             |
| <td></td>                                                             |
| <td></td>                                                             |
| <td></td>                                                             |
| <td></td>                                                             |
| <td colspan="2"></td>                                                 |
| <td></td>                                                             |
| <td></td>                                                             |
| <td></td>                                                             |
| </tr>                                                                 |
| </tbody>                                                              |
| </table>                                                              |
|                                                                       |
|                                                                       |
+-----------------------------------------------------------------------+
| \* AMSRE L2P "realtime" products (contain "\_rt\_"  in filename) from |
| Remote Sensing Systems (REMSS) can have partial orbits. A "-po*X*-"   |
| will be found in the filename:                                        |
+-----------------------------------------------------------------------+
| •      \"-po0-: the whole orbit                                       |
+-----------------------------------------------------------------------+
| •      -po1-: first section of orbit                                  |
+-----------------------------------------------------------------------+
| ·      -po2-: second section of orbit                                 |
+-----------------------------------------------------------------------+
| <table>                                                               |
| <colgroup>                                                            |
| <col style="width: 13%" />                                            |
| <col style="width: 10%" />                                            |
| <col style="width: 9%" />                                             |
| <col style="width: 15%" />                                            |
| <col style="width: 8%" />                                             |
| <col style="width: 10%" />                                            |
| <col style="width: 8%" />                                             |
| <col style="width: 9%" />                                             |
| <col style="width: 7%" />                                             |
| <col style="width: 6%" />                                             |
| </colgroup>                                                           |
| <tbody>                                                               |
| <tr class="odd">                                                      |
| <td><p><strong>Product</strong></p>                                   |
| <p><strong> </strong></p>                                             |
| <p><strong>[GHRSST product code]</strong></p></td>                    |
| <td><p><strong>Instrument</strong></p>                                |
| <p><strong>/ Type</strong></p></td>                                   |
| <td><strong>Satellite / Orbit</strong></td>                           |
| <td><strong>Data Source Agency</strong></td>                          |
| <td><strong>Data producer [RDAC code]</strong></td>                   |
| <td><blockquote>                                                      |
| <p><strong>Resolution</strong></p>                                    |
| </blockquote></td>                                                    |
| <td><p><strong>Latitude</strong></p>                                  |
| <p><strong>range</strong></p></td>                                    |
| <td><p><strong>Longitude</strong></p>                                 |
| <p><strong>range</strong></p></td>                                    |
| <td><strong>Files per day</strong></td>                               |
| <td><strong>Time Series</strong></td>                                 |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td colspan="10"><strong>L2P</strong></td>                            |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>AVHRR18_G</td>                                                    |
| <td>AVHRR / Infrared</td>                                             |
| <td>NOAA-18 / Polar</td>                                              |
| <td>NAVOCEANO</td>                                                    |
| <td>NAVO</td>                                                         |
| <td>8.8 km</td>                                                       |
| <td>90ºN -90ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td>14</td>                                                           |
| <td>Jan 2006 – present</td>                                           |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>AVHRR18_L</td>                                                    |
| <td>AVHRR / Infrared</td>                                             |
| <td>NOAA-18 / Polar</td>                                              |
| <td>NAVOCEANO</td>                                                    |
| <td>NAVO</td>                                                         |
| <td>2.2 km</td>                                                       |
| <td colspan="2">N America west and east coasts and various            |
| other</td>                                                            |
| <td>~30</td>                                                          |
| <td>Jan 2006 – present</td>                                           |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>AVHRRMTA_G</td>                                                   |
| <td>AVHRR / Infrared</td>                                             |
| <td>Envisat / Polar</td>                                              |
| <td>ESA</td>                                                          |
| <td>NAVO</td>                                                         |
| <td>9 km</td>                                                         |
| <td>90ºN -90ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td>14</td>                                                           |
| <td>Sept 2007 – present</td>                                          |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>NAR16_SST</td>                                                    |
| <td>AVHRR / Infrared</td>                                             |
| <td>NOAA-16 / Polar</td>                                              |
| <td>NAVOCEANO</td>                                                    |
| <td>EUR</td>                                                          |
| <td>2 km</td>                                                         |
| <td>78ºN -20ºS</td>                                                   |
| <td>45ºW - 45ºE</td>                                                  |
| <td>2</td>                                                            |
| <td>Feb 2005 – Nov 2005</td>                                          |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>NAR17_SST</td>                                                    |
| <td>AVHRR / Infrared</td>                                             |
| <td>NOAA-17 / Polar</td>                                              |
| <td>NAVOCEANO</td>                                                    |
| <td>EUR</td>                                                          |
| <td>2 km</td>                                                         |
| <td>78ºN -20ºS</td>                                                   |
| <td>45ºW - 45ºE</td>                                                  |
| <td>2</td>                                                            |
| <td>Feb 2005 – present</td>                                           |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>NAR18_SST</td>                                                    |
| <td>AVHRR / Infrared</td>                                             |
| <td>NOAA-18 / Polar</td>                                              |
| <td>NAVOCEANO</td>                                                    |
| <td>EUR</td>                                                          |
| <td>2 km</td>                                                         |
| <td>78ºN -20ºS</td>                                                   |
| <td>45ºW - 45ºE</td>                                                  |
| <td>2</td>                                                            |
| <td>Nov 2005 – present</td>                                           |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>MODIS_T</td>                                                      |
| <td>MODIS / Infrared</td>                                             |
| <td>Terra / Polar</td>                                                |
| <td>NASA OBPG/RSMAS/JPL</td>                                          |
| <td>JPL</td>                                                          |
| <td>1 km</td>                                                         |
| <td>90ºN -90ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td>~288</td>                                                         |
| <td>Oct 2006 - present</td>                                           |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>MODIS_A</td>                                                      |
| <td>MODIS / Infrared</td>                                             |
| <td>Aqua / Polar</td>                                                 |
| <td>NASA OBPG/RSMAS/JPL</td>                                          |
| <td>JPL</td>                                                          |
| <td>1 km</td>                                                         |
| <td>90ºN -90ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td>~288</td>                                                         |
| <td>Jul 2006 - present</td>                                           |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>GOES11</td>                                                       |
| <td>GOES Imager / Infrared</td>                                       |
| <td>GOES-11</td>                                                      |
| <td>NOAA</td>                                                         |
| <td>OSDPD</td>                                                        |
| <td>6 km</td>                                                         |
| <td>76ºN -50ºS</td>                                                   |
| <td>146E -59ºW</td>                                                   |
| <td>~48</td>                                                          |
| <td>Dec 2006 - present</td>                                           |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>GOES12</td>                                                       |
| <td>GOES Imager / Infrared</td>                                       |
| <td>GOES-12</td>                                                      |
| <td>NOAA</td>                                                         |
| <td>OSDPD</td>                                                        |
| <td>6 km</td>                                                         |
| <td>72ºN -55ºS</td>                                                   |
| <td>152W - 4ºE</td>                                                   |
| <td>~48</td>                                                          |
| <td>Dec 2006 - present</td>                                           |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>TMI</td>                                                          |
| <td>TMI / Microwave</td>                                              |
| <td>TRMM / Equatorial</td>                                            |
| <td>Remote Sensing Systems, Inc.</td>                                 |
| <td>EUR</td>                                                          |
| <td>25 km</td>                                                        |
| <td>38ºN -38ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td>~16</td>                                                          |
| <td>Feb 2005 – Feb 2007</td>                                          |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>TMI</td>                                                          |
| <td>TMI / Microwave</td>                                              |
| <td>TRMM / Equatorial</td>                                            |
| <td>Remote Sensing Systems, Inc.</td>                                 |
| <td>REMSS</td>                                                        |
| <td>25 km</td>                                                        |
| <td>38ºN -38ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td><p>14</p>                                                         |
| <p>(&amp; 14 realtime files)</p></td>                                 |
| <td>Jan 1998 – present</td>                                           |
| </tr>                                                                 |
| </tbody>                                                              |
| </table>                                                              |
|                                                                       |
|                                                                       |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+
| <table>                                                               |
| <colgroup>                                                            |
| <col style="width: 10%" />                                            |
| <col style="width: 10%" />                                            |
| <col style="width: 9%" />                                             |
| <col style="width: 9%" />                                             |
| <col style="width: 9%" />                                             |
| <col style="width: 9%" />                                             |
| <col style="width: 8%" />                                             |
| <col style="width: 10%" />                                            |
| <col style="width: 10%" />                                            |
| <col style="width: 11%" />                                            |
| </colgroup>                                                           |
| <tbody>                                                               |
| <tr class="odd">                                                      |
| <td><p><strong>Product</strong></p>                                   |
| <p><strong> </strong></p>                                             |
| <p><strong>[GHRSST product code]</strong></p></td>                    |
| <td><p><strong>Instrument</strong></p>                                |
| <p><strong>/ Type</strong></p></td>                                   |
| <td><strong>Satellite / Orbit</strong></td>                           |
| <td><strong>Data Source Agency</strong></td>                          |
| <td><strong>Data producer [RDAC code]</strong></td>                   |
| <td><blockquote>                                                      |
| <p><strong>Resolut-ion</strong></p>                                   |
| </blockquote></td>                                                    |
| <td><p><strong>Latitude</strong></p>                                  |
| <p><strong>range</strong></p></td>                                    |
| <td><p><strong>Longitude</strong></p>                                 |
| <p><strong>range</strong></p></td>                                    |
| <td><strong>Files per day</strong></td>                               |
| <td><strong>Time Series</strong></td>                                 |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td colspan="10"><strong>L3P/L2P_GRIDDED</strong></td>                |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>AMSRE</td>                                                        |
| <td>AMSRE / Microwave</td>                                            |
| <td>Aqua / Polar</td>                                                 |
| <td>Remote Sensing Systems, Inc.</td>                                 |
| <td>EUR</td>                                                          |
| <td>25 km</td>                                                        |
| <td>90ºN -90ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td><p>1</p>                                                          |
| <p>(&amp; 1 realtime file)</p></td>                                   |
| <td>Jun 2002 – present</td>                                           |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>TMI</td>                                                          |
| <td>TMI / Microwave</td>                                              |
| <td>TRMM / Equatorial</td>                                            |
| <td>Remote Sensing Systems, Inc.</td>                                 |
| <td>REMSS</td>                                                        |
| <td>25 km</td>                                                        |
| <td>38ºN -38ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td><p>1</p>                                                          |
| <p>(&amp; 1 realtimefile)</p></td>                                    |
| <td>Jan 1998 -present</td>                                            |
| </tr>                                                                 |
| </tbody>                                                              |
| </table>                                                              |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+
| <table>                                                               |
| <colgroup>                                                            |
| <col style="width: 16%" />                                            |
| <col style="width: 12%" />                                            |
| <col style="width: 8%" />                                             |
| <col style="width: 12%" />                                            |
| <col style="width: 8%" />                                             |
| <col style="width: 9%" />                                             |
| <col style="width: 8%" />                                             |
| <col style="width: 9%" />                                             |
| <col style="width: 5%" />                                             |
| <col style="width: 8%" />                                             |
| </colgroup>                                                           |
| <tbody>                                                               |
| <tr class="odd">                                                      |
| <td><p><strong>Product</strong></p>                                   |
| <p><strong> </strong></p>                                             |
| <p><strong>[GHRSST product code]</strong></p></td>                    |
| <td><strong>Region</strong></td>                                      |
| <td><strong>Source Data</strong></td>                                 |
| <td><strong>Producer Agency</strong></td>                             |
| <td><strong>Data producer [RDAC code]</strong></td>                   |
| <td><blockquote>                                                      |
| <p><strong>Resolut-ion</strong></p>                                   |
| </blockquote></td>                                                    |
| <td><p><strong>Latitude</strong></p>                                  |
| <p><strong>range</strong></p></td>                                    |
| <td><p><strong>Longitude</strong></p>                                 |
| <p><strong>range</strong></p></td>                                    |
| <td><strong>Files per day</strong></td>                               |
| <td><strong>Time Series</strong></td>                                 |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td colspan="10"><strong>L4</strong></td>                             |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>ODYSSEA</td>                                                      |
| <td>GLOB</td>                                                         |
| <td>AVHRR, AMSRE, TMI, AATSR, SEVIRI, GOES</td>                       |
| <td>CNES/Ifremere</td>                                                |
| <td>EUR</td>                                                          |
| <td>6 km</td>                                                         |
| <td>90ºN -90ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td><p>1</p>                                                          |
| <p> </p></td>                                                         |
| <td>Jan 2008 – present</td>                                           |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>AVHRR_OI</td>                                                     |
| <td>GLOB</td>                                                         |
| <td>AVHRR, in situ (buoys, ships)</td>                                |
| <td>NOAA</td>                                                         |
| <td>NCDC</td>                                                         |
| <td>0.25 deg</td>                                                     |
| <td>90ºN -90ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td><p>1</p>                                                          |
| <p> </p></td>                                                         |
| <td>Jan 1985 -present</td>                                            |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>AVHRR_AMSR_OI</td>                                                |
| <td>GLOB</td>                                                         |
| <td>AVHRR, AMSRE, in situ</td>                                        |
| <td>NOAA</td>                                                         |
| <td>NCDC</td>                                                         |
| <td>0.25 deg</td>                                                     |
| <td>90ºN -90ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td><p>1</p>                                                          |
| <p> </p></td>                                                         |
| <td>Jun 2002 – present</td>                                           |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>OSTIA</td>                                                        |
| <td>GLOB</td>                                                         |
| <td>AVHRR, AMSRE, TMI, AATSR, SEVIRI, in situ</td>                    |
| <td>UK Met Office</td>                                                |
| <td>UKMO</td>                                                         |
| <td>6 km</td>                                                         |
| <td>90ºN -90ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td><p>1</p>                                                          |
| <p> </p></td>                                                         |
| <td>Mar 2006 -present</td>                                            |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>mw_ir_OI</td>                                                     |
| <td>GLOB</td>                                                         |
| <td>AMSRE, TMI, MODIS</td>                                            |
| <td>Remote Sensing Systems</td>                                       |
| <td>REMSS</td>                                                        |
| <td>6 km</td>                                                         |
| <td>90ºN -90ºS</td>                                                   |
| <td>180ºW - 180ºE</td>                                                |
| <td><p>1</p>                                                          |
| <p> </p></td>                                                         |
| <td>Aug 2005 – present</td>                                           |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>ODYSSEA</td>                                                      |
| <td>MED</td>                                                          |
| <td>AVHRR, AMSRE, TMI, AATSR, SEVIRI</td>                             |
| <td>CNES/Ifremer</td>                                                 |
| <td>EUR</td>                                                          |
| <td>2 km</td>                                                         |
| <td>46.5ºN -30ºN</td>                                                 |
| <td>18.5ºW – 36.5ºE</td>                                              |
| <td><p>1</p>                                                          |
| <p> </p></td>                                                         |
| <td>Jan 2008 -present</td>                                            |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>ODYSSEA</td>                                                      |
| <td>GAL</td>                                                          |
| <td>AVHRR, AMSRE, TMI, AATSR, SEVIRI</td>                             |
| <td>CNES/Ifremere</td>                                                |
| <td>EUR</td>                                                          |
| <td>2 km</td>                                                         |
| <td>20ºN -20ºS</td>                                                   |
| <td>120ºW - 69ºE</td>                                                 |
| <td><p>1</p>                                                          |
| <p> </p></td>                                                         |
| <td>Jan 2008 – present</td>                                           |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>ODYSSEA</td>                                                      |
| <td>NWE</td>                                                          |
| <td>AVHRR, AMSRE, TMI, AATSR, SEVIRI</td>                             |
| <td>CNES/Ifremer</td>                                                 |
| <td>EUR</td>                                                          |
| <td>2 km</td>                                                         |
| <td>60ºN -43ºN</td>                                                   |
| <td>13ºW - 9ºE</td>                                                   |
| <td><p>1</p>                                                          |
| <p> </p></td>                                                         |
| <td>Jan 2008 -present</td>                                            |
| </tr>                                                                 |
| <tr class="odd">                                                      |
| <td>MED*</td>                                                         |
| <td>MED</td>                                                          |
| <td>AVHRR, AMSRE, TMI, AATSR, SEVIRI</td>                             |
| <td>CNES/Ifremere</td>                                                |
| <td>EUR</td>                                                          |
| <td>2 km</td>                                                         |
| <td>45.99ºN -30.01ºN</td>                                             |
| <td>5.99ºW – 36.49ºE</td>                                             |
| <td><p>1</p>                                                          |
| <p> </p></td>                                                         |
| <td>Jan 2005 – Jan 2008</td>                                          |
| </tr>                                                                 |
| <tr class="even">                                                     |
| <td>DMI_OI</td>                                                       |
| <td>NSEABLATIC</td>                                                   |
| <td><p>AVHRR, AMSRE,</p>                                              |
| <p>AATSR, SEVIRI</p></td>                                             |
| <td>Danish Met Inst</td>                                              |
| <td>DMI</td>                                                          |
| <td>2 km</td>                                                         |
| <td>65.98ºN - 48.01ºS</td>                                            |
| <td>9.99ºW - 30ºE</td>                                                |
| <td><p>1</p>                                                          |
| <p> </p></td>                                                         |
| <td>Jun 2007 -present</td>                                            |
| </tr>                                                                 |
| </tbody>                                                              |
| </table>                                                              |
|                                                                       |
|                                                                       |
+-----------------------------------------------------------------------+
| \* L4 MED product originally produced from 2005 to 2008 has been      |
| superceded by the ODYSSEA product for this region since Jan 2008      |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+
| **ACRYNOMS**                                                          |
+-----------------------------------------------------------------------+
| AATSR             Advanced Along Track Scanning Radiometer            |
+-----------------------------------------------------------------------+
| AMSRE                        Advanced Microwave Scanning Radiometer   |
| for EOS                                                               |
+-----------------------------------------------------------------------+
| AVHRR                        Advanced High Resolution Radiometer      |
+-----------------------------------------------------------------------+
| CNES               Centre National d'Etudes Spatiales                 |
+-----------------------------------------------------------------------+
| ESA                 European Space Agency                             |
+-----------------------------------------------------------------------+
| EUMETSAT      European Organisation for the Exploitation of           |
| Meteorological Satellites                                             |
+-----------------------------------------------------------------------+
| GOES               Geostationary Orbiting Environmental Satellite     |
+-----------------------------------------------------------------------+
| JPL                  Jet Propulsion Laboratory                        |
+-----------------------------------------------------------------------+
| MODIS             Moderate Resolution Imaging Spectrometer            |
+-----------------------------------------------------------------------+
| MSG                Meteosat Second Generation                         |
+-----------------------------------------------------------------------+
| NAVOCEANO   Naval Oceanographic Office                                |
+-----------------------------------------------------------------------+
| NASA               National Aeronautics and Space Administration      |
+-----------------------------------------------------------------------+
| NOAA              National Oceanic and Atmospherics Administration    |
+-----------------------------------------------------------------------+
| OBPG               Ocean Biology Processing Group                     |
+-----------------------------------------------------------------------+
| RSMAS                        Rosenstiel School of Marine and          |
| Atmospheric Science                                                   |
+-----------------------------------------------------------------------+
| SEVIRI             Spinning Enhanced Visible and Infrared Imager      |
+-----------------------------------------------------------------------+
| TMI                  TRMM Microwave Imager                            |
+-----------------------------------------------------------------------+
| TRMM             Tropical Rainfall Measuring Mission                  |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+
| **RDAC codes**                                                        |
+-----------------------------------------------------------------------+
| EUR                 European Medspiration Project                     |
+-----------------------------------------------------------------------+
| JPL                  NASA Jet Propulsion Laboratory                   |
+-----------------------------------------------------------------------+
| NAVO              NAVOCEANO                                           |
+-----------------------------------------------------------------------+
| NCDC              NOAA National Climatic Data Center                  |
+-----------------------------------------------------------------------+
| OSDPD             NOAA Office of Satellite Data Processing and        |
| Distribution                                                          |
+-----------------------------------------------------------------------+
| REMSS                        Remote Sensing Systems, Inc.             |
+-----------------------------------------------------------------------+
|                                                                       |
+-----------------------------------------------------------------------+
| **L4 Region Identifiers**                                             |
+-----------------------------------------------------------------------+
| GLOB:              Global Ocean                                       |
+-----------------------------------------------------------------------+
| MED                Mediterranean Sea                                  |
+-----------------------------------------------------------------------+
| NWE                Northwest Europe (Atlantic)                        |
+-----------------------------------------------------------------------+
| GAL                 Galapagos Islands (Pacific)                       |
+-----------------------------------------------------------------------+
| NSEABALTIC   North Sea and Baltic Sea                                 |
+-----------------------------------------------------------------------+

>  

 

### 2.3.4 What software can I use to read the data

Read software is available in C and IDL. Such software can be used in
designating appropriate flags, along with extraction parameters in
latitude and longitude. For programs in C please see:
<ftp://podaac.jpl.nasa.gov/GHRSST/software/L2P/C>. Software to read
Level 4 data may be found under:
<ftp://podaac.jpl.nasa.gov/GHRSST/software/L4/C>. For example software
please see appendix?

## 2.4 Complete GHRSST Data Formats 

###  2.4.1 Level 2 Preprocessed (L2P) 

The L2P format in netCDF is the standard for all GHRSST non-gridded
data. This format includes all the single sensor statistics (SSES) see
appendix 1, ancillary fields, confidence flags and other fields
associated with the GHRSST data. The structure, attributes, and
parameters contained in the netCDF are shown below.

+-------------------+------------------+-------------------------------+
| Name              | Definition       | Description                   |
+-------------------+------------------+-------------------------------+
| \<Date Valid\>    | YYYYMMDD         | Refers to the date for which  |
|                   |                  | this particular data set is   |
|                   |                  | valid for.                    |
+-------------------+------------------+-------------------------------+
| \<L0 ID\>         | AVHRR18_L        | Data set name                 |
|                   |                  |                               |
|                   | SEVIRI_SST       |                               |
|                   |                  |                               |
|                   | MODIS_A          |                               |
|                   |                  |                               |
|                   | ATS_NE_2P        |                               |
|                   |                  |                               |
|                   | GOES12           |                               |
|                   |                  |                               |
|                   | GOES11           |                               |
|                   |                  |                               |
|                   | AMSRE            |                               |
|                   |                  |                               |
|                   | TMI              |                               |
+-------------------+------------------+-------------------------------+
| \<Processing      | NAVO             | Processing centre code        |
| Centre Code\>     |                  |                               |
|                   | EUR              |                               |
|                   |                  |                               |
|                   | JPL              |                               |
|                   |                  |                               |
|                   | OSDPD            |                               |
|                   |                  |                               |
|                   | REMSS            |                               |
+-------------------+------------------+-------------------------------+
| \<SST filename\>  | Native to SST    | Filename of input SST data    |
|                   | filename         | file as given by data         |
|                   |                  | provider                      |
+-------------------+------------------+-------------------------------+
| \<optional        | string           | Free field to distinguish     |
| characteristic\>  |                  | ambiguous cases (such as      |
|                   |                  | ascending/descending pass     |
|                   |                  | when contained into a single  |
|                   |                  | L2 file)                      |
+-------------------+------------------+-------------------------------+
| \<processing      | vnn (where nn is | Version number of the GDS     |
| model ID\>        | the GDS version  | system used to process the    |
|                   | number, e.g., 01 | data file                     |
+-------------------+------------------+-------------------------------+
| \<base format\>   | nc               | Generic file format           |
|                   |                  | (nc=netCDF)                   |
+-------------------+------------------+-------------------------------+

The valid date component of the filename forms the first part of the
string so that data can be easily sorted by date. Examples of L2P files
for MODIS, AATSR, SEVIRI, AVHRR, GOES TMI and AMSRE are shown below:

20080407-AVHRR18_L-NAVO-L2P-SST_s1620_e1631-v01.nc

20080407-SEVIRI_SST-EUR-L2P-sst3mlml_20080407_0400-v01.nc

20080407-MODIS_A-JPL-L2P-A2008098063500.L2_LAC_GHRSST-v01.nc

20080405-ATS_NR_2P-EUR-L2P-ATS_NR\_\_2PNPDK20080405_122545_000060672067_00267_31884_7817.N1-v01.nc

20080404-GOES12-OSDPD-L2P-GOES12_South_2239Z-v01.nc

20080407-AMSRE-REMSS-L2P-amsr_l2b_rt_v05_r31531.dat-po0-v01.nc.

20080407-TMI-REMSS-L2P-tmi_L2b_rt_v04_059217.dat-v01.nc.gz

+-------------------------+---------------------------+---------------+
| Name                    | Description               | Units         |
+-------------------------+---------------------------+---------------+
| lon                     | Longitude of pixel        | Decimal       |
|                         |                           | Degrees       |
+-------------------------+---------------------------+---------------+
| lat                     | Latitude of pixel         | Decimal       |
|                         |                           | Degrees       |
+-------------------------+---------------------------+---------------+
| time                    | Time of pixel observation | Seconds       |
+-------------------------+---------------------------+---------------+
| sea_surface_temperature | Pixel SST values          | K             |
|                         |                           |               |
|                         | use attribute             |               |
|                         | \'sea_s                   |               |
|                         | urface_temperature:source |               |
|                         | = \"\...\"\' to specify   |               |
|                         | the L2 product source     |               |
+-------------------------+---------------------------+---------------+
| sst_dtime               | Deviation in seconds from | second        |
|                         | reference time defined as |               |
|                         | the time of the first L2P |               |
|                         | data record in this file  |               |
|                         | stored in the netCDF      |               |
|                         | global variable time.     |               |
|                         |                           |               |
|                         | It is implicit that there |               |
|                         | will be a 0 value and     |               |
|                         | sst_dtime is always       |               |
|                         | positive.                 |               |
+-------------------------+---------------------------+---------------+
| SSES_bias_error         | SSES Bias error based on  | K             |
|                         | confidence flags. ranges  |               |
|                         | from -1 to 1 degree,      |               |
|                         | precision 0.01 degree     |               |
+-------------------------+---------------------------+---------------+
| SSES_s                  | SSES standard deviation   | K             |
| tandard_deviation_error | error based on confidence |               |
|                         | flags. Ranges from 0 to   |               |
|                         | 1.5 K, precision 0.01 K   |               |
+-------------------------+---------------------------+---------------+
| DT_analysis             | Deviation from previous   | K             |
|                         | day (T-1) SSTfnd          |               |
|                         | analysis. If no analysis  |               |
|                         | is available, the         |               |
|                         | reference mean SST        |               |
|                         | climatology should be     |               |
|                         | used defined as R9 in     |               |
|                         | Table A3.3.1. Precision : |               |
|                         | 0.1 K                     |               |
+-------------------------+---------------------------+---------------+
| s                       | Near contemporaneous SSI  | Wm-2          |
| urface_solar_irradiance | value.                    |               |
|                         |                           |               |
|                         | if 6 hourly irradiance :  |               |
|                         | ranges from 0 to 500      |               |
|                         | Wm-2, precision 2 Wm-2    |               |
|                         |                           |               |
|                         | if 3 hourly irradiance :  |               |
|                         | ranges from 0 to 1000     |               |
|                         | Wm-2, precision 4 Wm-2    |               |
|                         |                           |               |
|                         | if unique source          |               |
|                         | (recommended), use        |               |
|                         | attribute                 |               |
|                         | \'surfac                  |               |
|                         | e_solar_irradiance:source |               |
|                         | = \"\...\"\'              |               |
+-------------------------+---------------------------+---------------+
| wind_speed              | Wind speed value. ranges  | ms-1          |
|                         | from 0 to 50m/s.          |               |
|                         | precision : 1 m/s. if     |               |
|                         | unique source             |               |
|                         | (recommended), use        |               |
|                         | attribute                 |               |
|                         | \'wind_speed:source =     |               |
|                         | \"\...\"\'                |               |
+-------------------------+---------------------------+---------------+
| sea_ice_fraction        | Fractional Sea Ice        | Percent       |
|                         | contamination flag.       |               |
|                         | Ranges from 0 to 1,       |               |
|                         | precision 0.01. if unique |               |
|                         | source (recommended), use |               |
|                         | attribute                 |               |
|                         | \'sea_ice_fraction:source |               |
|                         | = \"\...\"\'              |               |
+-------------------------+---------------------------+---------------+
| aerosol_optical_depth   | The Aeroptical depth due  | Scaled value. |
|                         | to extinction by the      |               |
|                         | aerosol component of the  |               |
|                         | atmosphere. Aerosol       |               |
|                         | optical depths typically  |               |
|                         | decrease with increasing  |               |
|                         | wavelength and are much   |               |
|                         | smaller for longwave      |               |
|                         | radiation than for        |               |
|                         | shortwave radiation.      |               |
|                         | Values vary widely        |               |
|                         | depending on atmospheric  |               |
|                         | conditions, but are       |               |
|                         | typically in the range    |               |
|                         | 0.02--0.2 for visible     |               |
|                         | radiation. See also       |               |
|                         | turbidity. Aerosol        |               |
|                         | optical depth. Aerosol    |               |
|                         | optical depth. if unique  |               |
|                         | source (recommended), use |               |
|                         | attribute                 |               |
|                         | \'aer                     |               |
|                         | osol_optical_depth:source |               |
|                         | = \"\...\"\'              |               |
+-------------------------+---------------------------+---------------+
| satellite_zenith_angle  | -90 to +90 degrees        | Degree        |
+-------------------------+---------------------------+---------------+
| rejection_flag          | Bit field:                | Flag          |
|                         |                           |               |
|                         | 0=SST out of range        |               |
|                         |                           |               |
|                         | 1=Cosmetic value          |               |
|                         |                           |               |
|                         | 2=IR_Cloudy               |               |
|                         |                           |               |
|                         | 3=MW_rain                 |               |
|                         |                           |               |
|                         | 4=MW_ice                  |               |
|                         |                           |               |
|                         | 5=MW_wind                 |               |
|                         |                           |               |
|                         | 6=Land                    |               |
|                         |                           |               |
|                         | 7=spare                   |               |
+-------------------------+---------------------------+---------------+
| sources_of_wind_speed   | Source of wind_speed      | Code          |
|                         | value. Source codes must  |               |
|                         | be detailed in the        |               |
|                         | 'sources_of_wind_speed:   |               |
|                         | comment' attribute. Must  |               |
|                         | be used when several      |               |
|                         | sources are mixed         |               |
|                         | together to fill up this  |               |
|                         | field.                    |               |
|                         |                           |               |
|                         | When a unique source is   |               |
|                         | used, it can be replace   |               |
|                         | by a variable attribute   |               |
|                         | of wind_speed variable as |               |
|                         | detailed.                 |               |
+-------------------------+---------------------------+---------------+
| sources_of_aod          | Source of AOD data.       | Code          |
|                         | Source codes must be      |               |
|                         | detailed in the           |               |
|                         | 'sources_of_aod: comment' |               |
|                         | attribute. Must be used   |               |
|                         | when several sources are  |               |
|                         | mixed together to fill up |               |
|                         | this field.               |               |
|                         |                           |               |
|                         | When a unique source is   |               |
|                         | used, it can be replace   |               |
|                         | by a variable attribute   |               |
|                         | of aerosol_optical_depth  |               |
|                         | variable as detailed.     |               |
+-------------------------+---------------------------+---------------+
| sources_of              | Source of Fractional sea  | Code          |
| sea_ice_fraction        | ice data. Source codes    |               |
|                         | must be detailed in the   |               |
|                         | 'sources_of               |               |
|                         | sea_ice_fraction:         |               |
|                         | comment' attribute. Must  |               |
|                         | be used when several      |               |
|                         | sources are mixed         |               |
|                         | together to fill up this  |               |
|                         | field.                    |               |
|                         |                           |               |
|                         | When a unique source is   |               |
|                         | used, it can be replace   |               |
|                         | by a variable attribute   |               |
|                         | of sea_ice_fraction       |               |
|                         | variable as detailed.     |               |
+-------------------------+---------------------------+---------------+
| sources_of_ssi          | Source of SSI data.       | Code          |
|                         | Source codes must be      |               |
|                         | detailed in the           |               |
|                         | 'sources_of_ssi: comment' |               |
|                         | attribute. Must be used   |               |
|                         | when several sources are  |               |
|                         | mixed together to fill up |               |
|                         | this field.               |               |
|                         |                           |               |
|                         | When a unique source is   |               |
|                         | used, it can be replace   |               |
|                         | by a variable attribute   |               |
|                         | of                        |               |
|                         | surface_solar_irradiance  |               |
|                         | variable as detailed.     |               |
+-------------------------+---------------------------+---------------+
| wi                      | Time difference of        | Scaled hours, |
| nd_speed_dtime_from_sst | wind_speed measurement    | 25=not known  |
|                         | from SST measurement      |               |
+-------------------------+---------------------------+---------------+
| aod_dtime_from_sst      | Time difference of AOD    | Scaled hours, |
|                         | measurement from SST      | 25=not known  |
|                         | measurement               |               |
+-------------------------+---------------------------+---------------+
| ssi_dtime_from_sst      | Time difference of SSI    | Scaled hours, |
|                         | measurement from SST      | 25=not known  |
|                         | measurement               |               |
+-------------------------+---------------------------+---------------+
| confidence_flag         | b0 : 1=potential side     | 8 Flags       |
|                         | lobe contamination;       |               |
|                         |                           |               |
|                         | b1 : 1=relaxed rain       |               |
|                         | contamination suspected;  |               |
|                         |                           |               |
|                         | b2 : 1=TMI SST retrieved  |               |
|                         | in SST \< 285K            |               |
|                         |                           |               |
|                         | b3 : 1=high wind speed    |               |
|                         | retrieval                 |               |
|                         |                           |               |
|                         | b4 : 1=sea ice retrieval  |               |
|                         | for MW data               |               |
|                         |                           |               |
|                         | b5 : 1= sun glint         |               |
|                         | suspected                 |               |
|                         |                           |               |
|                         | b6 : 1= L2 native bias    |               |
|                         | and standard deviation;   |               |
|                         |                           |               |
|                         | b7 : 1= L2 native         |               |
|                         | confidence value \" ;     |               |
+-------------------------+---------------------------+---------------+
| proximity_confidence    | Proximity confidence      | Code          |
|                         | value                     |               |
+-------------------------+---------------------------+---------------+
| New additional fields   | Space to provide R&D      | Defined by    |
| may be added by L2P     | fields that are in        | RDAC          |
| data providers if they  | development for GDS-v2.0. |               |
| are really relevant for | E.g. MODIS could provide  |               |
| users. However the new  | an estimate of            |               |
| fields shall not        | Chlorphyll, to accompany  |               |
| increase L2P file size  | the SST, diurnal          |               |
| by more than 6 bytes.   | variability work, sea ice |               |
| These New fields and    | experiments. 6-bytes are  |               |
| there related           | available in any          |               |
| properties (variable    | coimbinatkion (i.e., 6x   |               |
| name, unit,...) must be | byte, 3 x short, 1 x      |               |
| approved by GHRSST-PO   | long + 1 x int etc. These |               |
| in order to keep the    | fields will be used to    |               |
| consistency of the      | test new ideas for        |               |
| various datasets        | GDS-v2.0 and provide a    |               |
| (agreeing for instance  | limited amounmt of        |               |
| on common standard      | flexibility within the    |               |
| names for the new       | GDS for regional user     |               |
| variables,...). They    | requirements. Flexibility |               |
| shall also be           | is provided through the   |               |
| documented at GHRSST-PO | netCDF API which allows   |               |
| as an annex to the      | fully self-describing     |               |
| current GDS version.    | fields.                   |               |
|                         |                           |               |
|                         | Use of this field implies |               |
|                         | documentation. The        |               |
|                         | GHRSST-PO will publish    |               |
|                         | the current use of this   |               |
|                         | field by RDAC teams on    |               |
|                         | the GHRSST-PP web site,   |               |
|                         | The fields must be        |               |
|                         | documented for the LTSRF  |               |
|                         | system and re-analysis as |               |
|                         | well as a sanity check    |               |
|                         | for the GHRSST-PP as a    |               |
|                         | whole. As an ABSOLUTE     |               |
|                         | MINIMUM, the attributes   |               |
|                         | for this field should be  |               |
|                         | completed including       |               |
|                         |                           |               |
|                         | \(a\) title of field      |               |
|                         |                           |               |
|                         | \(b\) structure of the    |               |
|                         | field (bytes, floats,     |               |
|                         | scale factors etc),       |               |
|                         |                           |               |
|                         | \(c\) the field content   |               |
|                         | (what is it, what are the |               |
|                         | units)                    |               |
|                         |                           |               |
|                         | \(d\) comment on how to   |               |
|                         | use the field             |               |
|                         |                           |               |
|                         | e.g.                      |               |
|                         |                           |               |
|                         | TITLE: DT_Diurnal         |               |
|                         |                           |               |
|                         | STRUCTURE: 3 x short_int  |               |
|                         |                           |               |
|                         | CONTENT: int#1: estimated |               |
|                         | deviation from L2P SST    |               |
|                         | due to diurnal warming    |               |
|                         | computed using Kantha     |               |
|                         | Clayson model, uinits K,  |               |
|                         | INT#2: standard deviation |               |
|                         | of DT_diurnal estimate,   |               |
|                         | units K, INT#3: quality   |               |
|                         | flag of DT_diurnal 0=bad, |               |
|                         | 1=acceptable,2=good,      |               |
|                         | 3=excellent               |               |
|                         |                           |               |
|                         | USAGE: Subtract           |               |
|                         | DT_Diurnal from L2P SST   |               |
|                         | to obtain an estimate of  |               |
|                         | SSTfnd. DT_Diurnal has    |               |
|                         | been computed for each    |               |
|                         | satellite data stream     |               |
|                         | separely.                 |               |
+-------------------------+---------------------------+---------------+

**Table 1: Description of L2P format array attributes**

+--------------------+-----------------+-------------------------------+
| Tag name           | Format          | Description                   |
+====================+=================+===============================+
| Conventions        | string          | A text string identifying the |
|                    |                 | netCDF convention followed.   |
|                    |                 | This attribute should be set  |
|                    |                 | to \"CF-1.0\" to indicate     |
|                    |                 | compatibility with the        |
|                    |                 | Climate and Forecast (CF)     |
|                    |                 | netCDF convention.            |
+--------------------+-----------------+-------------------------------+
| title              | string          | A descriptive title for the   |
|                    |                 | data set                      |
+--------------------+-----------------+-------------------------------+
| DSD_entry_id       | string          | the DSD entry related to the  |
|                    |                 | data file, e.g.               |
|                    |                 | USA-RSS-AMSRE-MW-L2-SST       |
+--------------------+-----------------+-------------------------------+
| references         | String          | References that describe the  |
|                    |                 | data or the methods used to   |
|                    |                 | produce it. Include here the  |
|                    |                 | names of all GDS              |
|                    |                 | configuration files that have |
|                    |                 | been used.                    |
+--------------------+-----------------+-------------------------------+
| institution        | string          | GHRSST-PP data centre code    |
|                    |                 | (see Appendix A2 Table A2. 1) |
|                    |                 | where the data were produced  |
+--------------------+-----------------+-------------------------------+
| contact            | string          | A free text string giving the |
|                    |                 | primary contact for           |
|                    |                 | information about the data    |
|                    |                 | set                           |
+--------------------+-----------------+-------------------------------+
| GDS_version_id     | String          | v1r1.4b (to be updated)       |
+--------------------+-----------------+-------------------------------+
| netcdf_version_id  | String          | 3.5                           |
+--------------------+-----------------+-------------------------------+
| creation_date      | string          | Date the data file was        |
|                    | ,\"yyyy-mm-dd\" | created (UTC)                 |
+--------------------+-----------------+-------------------------------+
| product_version    | string          | Release number of the         |
|                    |                 | datafile (File_Version in the |
|                    |                 | MMR-FR, see A6.3.2)           |
+--------------------+-----------------+-------------------------------+
| history            | string          | List of the applications that |
|                    |                 | have modified the original    |
|                    |                 | data                          |
+--------------------+-----------------+-------------------------------+
| platform           | string          | Satellite identifier          |
+--------------------+-----------------+-------------------------------+
| sensor             | string          | Sensor identifier             |
+--------------------+-----------------+-------------------------------+
| spatial_resolution | string          | Resolution of the product     |
+--------------------+-----------------+-------------------------------+
| start_time         | string,         | Time of the first measurement |
|                    | "hh:mm:ss UTC"  | in the data file              |
+--------------------+-----------------+-------------------------------+
| stop_time          | string,         | Time of the last measurement  |
|                    | "hh:mm:ss UTC"  | in the data file              |
+--------------------+-----------------+-------------------------------+
| start_date         | stri            | Start date of the data in     |
|                    | ng,\"yyyy-mm-dd | universal time coordinated    |
|                    | UTC\"           | (UTC; \~ Greenwich Mean Time) |
+--------------------+-----------------+-------------------------------+
| stop_date          | stri            | End date of the data in       |
|                    | ng,\"yyyy-mm-dd | universal time coordinated    |
|                    | UTC\"           | (UTC; \~ Greenwich Mean       |
|                    |                 | Time).                        |
+--------------------+-----------------+-------------------------------+
| nor                | Float           | degrees north, range -90° to  |
| thernmost_latitude |                 | +90°                          |
+--------------------+-----------------+-------------------------------+
| sou                | Float           | degrees north, range -90° to  |
| thernmost_latitude |                 | +90°                          |
+--------------------+-----------------+-------------------------------+
| eas                | Float           | degrees east, range -180° to  |
| ternmost_longitude |                 | +180°                         |
+--------------------+-----------------+-------------------------------+
| wes                | Float           | degrees east, range -180° to  |
| ternmost_longitude |                 | +180°                         |
+--------------------+-----------------+-------------------------------+
| file_quality_index | integer         | A code value :\               |
|                    |                 | 0 : unknown quality\          |
|                    |                 | 1: excellent (no known        |
|                    |                 | problems)\                    |
|                    |                 | 2 : suspect (occasional       |
|                    |                 | problems, e.g. after launch)\ |
|                    |                 | 3 : extremely suspect         |
|                    |                 | (frequent problems, e.g.with  |
|                    |                 | known satellite problems)     |
+--------------------+-----------------+-------------------------------+
| source_data        | string \[1024\] | Comma separated list of       |
|                    |                 | source data present in this   |
|                    |                 | file. SST sources followed by |
|                    |                 | Auxillary sources. Source     |
|                    |                 | data identifiers are taken    |
|                    |                 | from Table A2.2. e.g., for an |
|                    |                 | L2P file we might expect      |
|                    |                 | something like:               |
|                    |                 |                               |
|                    |                 | ATS_NR\_\_2P,SEVIRI_SSI,O     |
|                    |                 | SISAF_ICE,NESDIS_AOD,UKMO_WSP |
|                    |                 |                               |
|                    |                 | For an L4 product we may      |
|                    |                 | expect something like:        |
|                    |                 |                               |
|                    |                 | ATS_NR\_\_2P,AVHRR16          |
|                    |                 | _G,SEVIRI,AMSRE,SEVIRI_SSI,OS |
|                    |                 | ISAF_ICE,NESDIS_AOD,UKMO_WSP, |
|                    |                 | AMSRE_ICE, AMSRE_WSP          |
+--------------------+-----------------+-------------------------------+
| comment            | string          | Miscellaneous information     |
+--------------------+-----------------+-------------------------------+

**Table 2: Description of l2P format global attributes**

  ---------------------------------------------------------------------------------------------------------
  Tag name        Format                   Description
  --------------- ------------------------ ----------------------------------------------------------------
  \_FillValue     Depends on variable type A value used to indicate array elements containing no valid
                                           data. This must be of the same type than the storage (packed)
                                           type; should be set as the minimum value for this type. Note
                                           that some netCDF readers are unable to cope with signed bytes
                                           and may, in these cases, report fill as 128

  units           string                   Text description of the units, preferably S.I., and must be
                                           compatible with the Unidata UDUNITS package. For a given
                                           variable (e.g. wind speed), these must be the same for each
                                           dataset.

  scale_factor    must be expressed in the To be multiplied by the variable to recover the original value.
                  unpacked data type (for  Defined by RDAC
                  instance float whereas   
                  the variable may be      
                  stored - or packed - as  
                  an array of short)       

  add_offset      must be expressed in the To be added to the variable after multiplying by the scale
                  unpacked data type (for  factor to recover the original value. If only one of
                  instance float whereas   scale_factor or add_offset are needed, then both should be
                  the variable may be      included anyway to avoid ambiguity, with scale_factor defaulting
                  stored - or packed - as  to 1.0 and add_offset defaulting to 0.0. Defined by RDAC
                  an array of short)       

  long_name       string                   A long version of the variable name

  valid_min       Same data type as        Minimum valid value for this variable once they are packed (in
                  variable                 storage type). The fill value should be outside this valid
                                           range. Note that some netCDF readers are unable to cope with
                                           signed bytes and may, in these cases, report valid min as 129

  valid_max       Same data type as        Maximum valid value for this variable once they are packed (in
                  variable                 storage type). The fill value should be outside this valid
                                           range. Note that some netCDF readers are unable to cope with
                                           signed bytes and may, in these cases, report valid min as 127

  standard_name   string                   A standard and unique description of a physical quantity. For
                                           the complete list of standard name strings, see
                                           <http://www.cgd.ucar.edu/cms/eaton/netcdf/standard_name.html>.

  source          string                   Method of production of the original data or original provider

  axis            string                   Identifies latitude, longitude, vertical or time axis

  positive        string                   Indicates the real-world direction of a coordinate variable
                                           (\"up\" or \"down\"). E.g., a depth or atmospheric pressure
                                           coordinate would have this attribute set to \"down\".

  coordinates     string                   Identifies auxiliary coordinate variables, such as 2-D lat-lon
                                           coordinate arrays, label variables, and alternative coordinate
                                           variables.

  grid_mapping    string                   Identifies a variable that defines a grid mapping must be
                                           provided if data mapped following a projection. refer to CF
                                           convention for standard projection names.

  comment         string                   Miscellaneous information about the data or the methods used to
                                           produce it
  ---------------------------------------------------------------------------------------------------------

**Table 3: Description of netCDF mandatory attributes**

### 2.4.2 Level 4 Analyzed Fields

L4 analysed data products, L4 are derived from an analysis procedure
based on L2P and other SST data products produced at regular (daily,
six-hourly or other (e.g., APPW)) time periods. L4 data products are
formatted as netCDF format data files and include ancillary data and
error statistics for each grid-cell. A six-byte experimental block is
available for data providers to test new aspects of the file or
information specific to the analysis system that will eventually
transition into a GHRSST-PP standard L4 analysis field once tested.

L4 global/variable attributes and the coordinate variables are
equivalent to L2P products format requirements (netCDF format, complying
to CF-1.0 convention) as laid out in Appendix A1 (GDS data product
format specification).

The GDS filename convention used for L4 data products has been designed
to provide useful information in an easily readable format. All L4 data
product filenames are derived according to the following convention:

\<Date Valid\>-\<Processing Centre Code\>-L4\<Product
type\>-\<Area\>-\<Processing Model ID\>-\<FileVersion\>.\<base format\>

which is defined in Table 2.

+------------------+-------------------+---------------------------+---+
| Name             | Definition        | Description               |   |
+------------------+-------------------+---------------------------+---+
| \<Date Valid\>   | YYYYMMDD          | Refers to the date for    |   |
|                  |                   | which this particular     |   |
|                  |                   | data set                  |   |
+------------------+-------------------+---------------------------+---+
| \<Processing     | UKMO              | Processing centre code    |   |
| Centre Code\>    |                   |                           |   |
|                  | NAVO              |                           |   |
|                  |                   |                           |   |
|                  | NCDC              |                           |   |
|                  |                   |                           |   |
|                  | REMSS             |                           |   |
|                  |                   |                           |   |
|                  | EUR               |                           |   |
+------------------+-------------------+---------------------------+---+
| \<product type\> | \"LR\"=low        | Resolution of analysed    |   |
|                  | resolution,       | foundation SST (fnd) data |   |
|                  | \"HR\"=high       |                           |   |
|                  | resolution or     |                           |   |
|                  |                   |                           |   |
|                  | \"UH\"=ultra-high |                           |   |
|                  | resolution        |                           |   |
|                  | followed by       |                           |   |
|                  | either fnd (for   |                           |   |
|                  | foundation SST),  |                           |   |
|                  |                   |                           |   |
|                  | skin, subskin,    |                           |   |
|                  | blend (for        |                           |   |
|                  | blended SST) or   |                           |   |
|                  | 1m, 2m, \.... ,   |                           |   |
|                  | 10m (for SST at   |                           |   |
|                  |                   |                           |   |
|                  | specific depth).  |                           |   |
|                  | UH\<=5km,         |                           |   |
|                  | HR\<=10km,        |                           |   |
|                  | LR\>10km.         |                           |   |
+------------------+-------------------+---------------------------+---+
| \<Area\>         | GLOB              | The area covered by the   |   |
|                  |                   | L4 product                |   |
|                  | MED               |                           |   |
|                  |                   |                           |   |
|                  | NSEABALTIC        |                           |   |
|                  |                   |                           |   |
|                  | NEW               |                           |   |
|                  |                   |                           |   |
|                  | AUS               |                           |   |
+------------------+-------------------+---------------------------+---+
| \<processing     | vnn (where nn is  | Version number of the GDS |   |
| model ID\>       | the GDS version   | system used to process    |   |
|                  | number, e.g., 01  | the data file             |   |
+------------------+-------------------+---------------------------+---+
| \<FileVersion\>  | Fv*xx.x* (where   | Release version for this  |   |
|                  | xx.x is the       | L4 file                   |   |
|                  | release number of |                           |   |
|                  | this              |                           |   |
|                  | file.g.fv11.3     |                           |   |
+------------------+-------------------+---------------------------+---+
| \<Additonal      | Free text to      | This text is used since   |   |
| Segregator\>     | distinguish       | the other codes are often |   |
|                  | between files     | insufficient to uniquely  |   |
|                  | with the same     | identify a file. For      |   |
|                  | \<Identifying     | example, in L2_GHRSST or  |   |
|                  | Code\> eg: OSTIA, | L3_GHRSST (uncollated)    |   |
|                  | ODYSSEA           | products this is often    |   |
|                  |                   | the original file name or |   |
|                  |                   | processing algorithm      |   |
|                  |                   | (note, underscores are    |   |
|                  |                   | used, not dashes).        |   |
+------------------+-------------------+---------------------------+---+
| \<base format\>  | Nc                | Generic file format       |   |
|                  |                   | (nc=netCDF)               |   |
+------------------+-------------------+---------------------------+---+

**Table 4: L4 product filenames**

Examples include;

20080406-UKMO-L4HRfnd-GLOB-v01-fv02-OSTIA.nc

20080407-NAVO-L4HR1m-GLOB-v01-fv01_0-K10_SST.nc

20080406-NCDC-L4LRblend-GLOB-v01-fv01_0-AVHRR_OI.nc

20061231-REMSS-L4HRfnd-GLOB-v01-fv01-mw_ir_OI.nc

20080113-EUR-L4UHFnd-MED-v01.nc

20080407-EUR-L4UHRfnd-MED-v01-fv01-ODYSSEA.nc

20080407-DMI-L4UHfnd-NSEABALTIC-v01-fv01-DMI_OI.nc

20040621-EUR-L4UHfnd-MED-v01-fv11.6.nc

20080331-ABOM-L4HRfnd-AUS-v01-fv01_0-RAMSSA_09km.nc

Refers to a data set valid on 21st June 2004 (20040621) generated at the
European RDAC (EUR), the data is an estimate of the foundation SST at
ultra-high resolution(L4UHfnd) covering the Mediterranean area (MED), it
was generated using GDS version 1 (v01), it is release 11.6 of the file
(implies considerable re-processing) and is formatted as a GHRSST-PP
netCDF file (.nc)

+------------------+-------------------+-------------------------------+
| Code             | Definition        | Description                   |
+------------------+-------------------+-------------------------------+
| GLOB             | 90°S to 90°N and  | Global coverer age data sets  |
|                  | from 180°W -      |                               |
|                  | 180°E             |                               |
+------------------+-------------------+-------------------------------+
| MED              | 30°N to 46°N and  | Mediterranean sea area        |
|                  | from 6°W to       |                               |
|                  | 36.5°E            |                               |
+------------------+-------------------+-------------------------------+
| EUR              | 70°S to 90°N and  | European RDAC area served by  |
|                  | from 100°W to     | the ESA Medspiration project  |
|                  | 45°E              |                               |
+------------------+-------------------+-------------------------------+
| AUS              | 70S to 20N and    | BoM Australian regional       |
|                  | from              | analysis                      |
|                  |                   |                               |
|                  | 60E to 170W.      |                               |
+------------------+-------------------+-------------------------------+

**Table 5: Description of example L4 product filename area code
definitions**

Table 6 describes the format of the L4 file variables associated with
each grid cell.

+----------------------------+-------------------------------+---------+
| Name                       | Description                   | Units   |
+----------------------------+-------------------------------+---------+
| analysed_sst               | SST from analysis system      | K,      |
|                            |                               | scaled  |
|                            |                               | 2 byte  |
|                            |                               | int     |
+----------------------------+-------------------------------+---------+
| analysis_error             | Error standard deviation      | K,      |
|                            | estimate output from the      | scaled  |
|                            | analysis system               | 2 byte  |
|                            |                               | int     |
+----------------------------+-------------------------------+---------+
| mask                       | 0=grid cell is open water     | Flag    |
|                            |                               | \[      |
|                            | 1=land in grid                | 8bits\] |
|                            |                               |         |
|                            | 2=lake surface in grid cell,  |         |
|                            |                               |         |
|                            | 3=ice in grid cell            |         |
|                            |                               |         |
|                            | Bits \[4-7\] spare.           |         |
+----------------------------+-------------------------------+---------+
| sea_ice_fraction           | Fractional Sea Ice area       | 0-1     |
|                            | concentration. Optional when  | scaled  |
|                            | covered area never contains   | byte    |
|                            | sea ice.                      |         |
+----------------------------+-------------------------------+---------+
| sources_of                 | Source of Fractional sea ice  | Code    |
| sea_ice_fraction           | data should be same           |         |
|                            | definition as for L2P. Should |         |
|                            | be replaced by a variable     |         |
|                            | attribute of sea_ice_fraction |         |
|                            | when single source.           |         |
+----------------------------+-------------------------------+---------+
| Experimental field         | Each grid cell has a 6 byte   | 6 bytes |
|                            | storage space available for   | (m      |
|                            | RDACs and other users to      | aximum) |
|                            | incluse specific information. | Defined |
|                            | The policy for use of these   | by data |
|                            | fields is that they should    | pro     |
|                            | make a useful contribution to | viders. |
|                            | the data sets and to          |         |
|                            | GHRSST-PP. Ideally            |         |
|                            | experimental fields should    |         |
|                            | transition into full fields   |         |
|                            | once stable and agreed by the |         |
|                            | GHRSS-PP Science Team. Use of |         |
|                            | these fields requires that a  |         |
|                            | description of the content    |         |
|                            | and specification is agreed   |         |
|                            | with the GHRSST-PP Data       |         |
|                            | Management Technical Advisory |         |
|                            | group and that CF-1.0         |         |
|                            | compliant attributes are      |         |
|                            | included in the file.         |         |
+----------------------------+-------------------------------+---------+

Table 5: generic L4 SST Variables

The variable 'analysed_sst' will be included with the format
requirements shown in Table A1.3.3.2.

Table A5 CDL description of analysed_sst variable

+-------+---------------------+-------------------------------+------+
|       | Name                | Description                   | Unit |
+-------+---------------------+-------------------------------+------+
|       | analysed_sst        | SST values from analysis      | Ke   |
|       |                     | systems                       | lvin |
+-------+---------------------+-------------------------------+------+
|       |                     |                               |      |
+-------+---------------------+-------------------------------+------+
|       |                     |                               |      |
+-------+---------------------+-------------------------------+------+
| Com   |                     |                               |      |
| ments |                     |                               |      |
+-------+---------------------+-------------------------------+------+
| Code  |                     |                               |      |
| d     |                     |                               |      |
| efini |                     |                               |      |
| tions |                     |                               |      |
| for   |                     |                               |      |
| an    |                     |                               |      |
| alyse |                     |                               |      |
| d_sst |                     |                               |      |
| :type |                     |                               |      |
| (see  |                     |                               |      |
| GHRS  |                     |                               |      |
| ST-PP |                     |                               |      |
| SST   |                     |                               |      |
| d     |                     |                               |      |
| efini |                     |                               |      |
| tions |                     |                               |      |
| in    |                     |                               |      |
| Se    |                     |                               |      |
| ction |                     |                               |      |
| 2 of  |                     |                               |      |
| the   |                     |                               |      |
| GDS   |                     |                               |      |
| (     |                     |                               |      |
| Notat |                     |                               |      |
| ions, |                     |                               |      |
| c     |                     |                               |      |
| onven |                     |                               |      |
| tions |                     |                               |      |
| and   |                     |                               |      |
| d     |                     |                               |      |
| efini |                     |                               |      |
| tions |                     |                               |      |
| used  |                     |                               |      |
| by    |                     |                               |      |
| the   |                     |                               |      |
| G     |                     |                               |      |
| DS)): |                     |                               |      |
|       |                     |                               |      |
|   --- |                     |                               |      |
| ----- |                     |                               |      |
| ----- |                     |                               |      |
| -- -- |                     |                               |      |
| ----- |                     |                               |      |
| ----- |                     |                               |      |
| ----- |                     |                               |      |
|   *   |                     |                               |      |
| *type |                     |                               |      |
| **    |                     |                               |      |
|       |                     |                               |      |
| **Des |                     |                               |      |
| cript |                     |                               |      |
| ion** |                     |                               |      |
|       |                     |                               |      |
|   ski |                     |                               |      |
| n     |                     |                               |      |
|       |                     |                               |      |
|    Sk |                     |                               |      |
| in su |                     |                               |      |
| rface |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|     t |                     |                               |      |
| emper |                     |                               |      |
| ature |                     |                               |      |
|       |                     |                               |      |
|   sub |                     |                               |      |
| skin  |                     |                               |      |
|       |                     |                               |      |
|    Su |                     |                               |      |
| bskin |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|     t |                     |                               |      |
| emper |                     |                               |      |
| ature |                     |                               |      |
|       |                     |                               |      |
|   f   |                     |                               |      |
| ounda |                     |                               |      |
| tion  |                     |                               |      |
|       |                     |                               |      |
| Found |                     |                               |      |
| ation |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|     t |                     |                               |      |
| emper |                     |                               |      |
| ature |                     |                               |      |
|       |                     |                               |      |
|   de  |                     |                               |      |
| pth_b |                     |                               |      |
| lende |                     |                               |      |
| d   T |                     |                               |      |
| emper |                     |                               |      |
| ature |                     |                               |      |
|  from |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|   a b |                     |                               |      |
| lende |                     |                               |      |
| d SST |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|  anal |                     |                               |      |
| ysis  |                     |                               |      |
| valid |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|     o |                     |                               |      |
| ver t |                     |                               |      |
| he su |                     |                               |      |
| rface |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|     o |                     |                               |      |
| cean  |                     |                               |      |
| in a  |                     |                               |      |
| layer |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|     w |                     |                               |      |
| ith u |                     |                               |      |
| nspec |                     |                               |      |
| ified |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
| depth |                     |                               |      |
|       |                     |                               |      |
|   1   |                     |                               |      |
| m     |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
| SST a |                     |                               |      |
| t 1m  |                     |                               |      |
| depth |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|  (SST |                     |                               |      |
| ~1m~) |                     |                               |      |
|       |                     |                               |      |
|   2   |                     |                               |      |
| m     |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
| SST a |                     |                               |      |
| t 2m  |                     |                               |      |
| depth |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|  (SST |                     |                               |      |
| ~2m~) |                     |                               |      |
|       |                     |                               |      |
|   3   |                     |                               |      |
| m     |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
| SST a |                     |                               |      |
| t 3m  |                     |                               |      |
| depth |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|  (SST |                     |                               |      |
| ~3m~) |                     |                               |      |
|       |                     |                               |      |
|   4   |                     |                               |      |
| m     |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
| SST a |                     |                               |      |
| t 4m  |                     |                               |      |
| depth |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|  (SST |                     |                               |      |
| ~4m~) |                     |                               |      |
|       |                     |                               |      |
|   5   |                     |                               |      |
| m     |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
| SST a |                     |                               |      |
| t 5m  |                     |                               |      |
| depth |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|  (SST |                     |                               |      |
| ~5m~) |                     |                               |      |
|       |                     |                               |      |
|   6   |                     |                               |      |
| m     |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
| SST a |                     |                               |      |
| t 6m  |                     |                               |      |
| depth |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|  (SST |                     |                               |      |
| ~6m~) |                     |                               |      |
|       |                     |                               |      |
|   7   |                     |                               |      |
| m     |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
| SST a |                     |                               |      |
| t 7m  |                     |                               |      |
| depth |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|  (SST |                     |                               |      |
| ~7m~) |                     |                               |      |
|       |                     |                               |      |
|   8   |                     |                               |      |
| m     |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
| SST a |                     |                               |      |
| t 8m  |                     |                               |      |
| depth |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|  (SST |                     |                               |      |
| ~8m~) |                     |                               |      |
|       |                     |                               |      |
|   9   |                     |                               |      |
| m     |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
| SST a |                     |                               |      |
| t 9m  |                     |                               |      |
| depth |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|  (SST |                     |                               |      |
| ~9m~) |                     |                               |      |
|       |                     |                               |      |
|   10  |                     |                               |      |
| m     |                     |                               |      |
|       |                     |                               |      |
|     S |                     |                               |      |
| ST at |                     |                               |      |
|  10m  |                     |                               |      |
| depth |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
|       |                     |                               |      |
| (SST~ |                     |                               |      |
| 10m~) |                     |                               |      |
|   --- |                     |                               |      |
| ----- |                     |                               |      |
| ----- |                     |                               |      |
| -- -- |                     |                               |      |
| ----- |                     |                               |      |
| ----- |                     |                               |      |
| ----- |                     |                               |      |
+-------+---------------------+-------------------------------+------+

### 2.4.3 GDSV2.0 L2, L3, and L4 File Naming Conventions

It is anticipated that GDSV2.0 will be implemented in the near future.
Striving to achieve a more flexible naming convention that maintains
consistency across data processing levels and better serves user needs,
the GDS 2.0 will use a single form for all GHRSST files:

\<Date Valid\>-\<RDAC\>-L\<X\>\<OPTIONALCODE\>\_GHRSST-\<Product
Type\>-\<Identifying Code\>-\<Additional Segregator\>-v\<GDS
Version\>-fv\<File Version\>.nc

The variable components within braces ( "\< \>") are defined in Table 1
below.

  ------------------ ------------------------- ----------------------------
  Name               Definition                Description

  \<Date Valid\>     YYYYMMDD                  Refers to the identifying
                                               date for this particular
                                               data set

  \<RDAC\>           The RDAC where the file   Processing centre code,
                     was created               defined in a GDS Appendix

  \<X\>              GHRSST Data Processing    Refers to the data
                     Level (X = 2, 3, or 4)    processing level, defined at
                                               the beginning of this
                                               proposal.

  \<OPTIONALCODE\>   An optional,              An optional one character
                     single-character          long code. For example, if
                                               set to "P" for a Level 2
                                               file, the name would now
                                               contain "L2P_GHRSST" instead
                                               of simply "L2_GHRSST"

  \<Product Type\>   The type of SST data      Conforms to the GHRSST
                     included in the file.     definitions for SST, for
                                               example: SST1m, SSTfnd,
                                               SSTsubskin, SSTblend,
                                               SSTskin

  \<Identifying      A unique code identifying The unique "name" (within an
  Code\>             the SST product set.      RDAC) of the product line.
                                               (L2_GHRSST examples:
                                               AVHRR18_G, AMSRE; L3_GHRSST
                                               examples: NAR_AVHRR_METOP_A,
                                               GLOB_AVHRR_METOP_A; and
                                               L4_GHRSST examples: OSTIA,
                                               AVHRR_OI (note, underscores
                                               are used, not dashes)

  \<Additional       Free text to distinguish  This text is used since the
  Segregator\>       between files with the    other codes are often
                     same \<Identifying Code\> insufficient to uniquely
                                               identify a file. For
                                               example, in L2_GHRSST or
                                               L3_GHRSST (uncollated)
                                               products this is often the
                                               original file name or
                                               processing algorithm (note,
                                               underscores are used, not
                                               dashes).

  \<GDS Version\>    *nn.n*                    Version number of the GDS
                                               used to process the data
                                               file

  \<FileVersion\>    *xx.x*                    Version number for this file
  ------------------ ------------------------- ----------------------------

**Table 6: GDS 2.0 File naming convention components**

Changes in GDSv2.0 include the definitions of L2_GHRSST, L3_GHRSST,
L4_GHRSST, as apposed to L2P, L3, and L4.

# 

# 3. 0 Methods for Accessing Data

## 3.1 OPenDAP

Data is available through OPenDAP through <http://dods.jpl.nasa.gov/> at
the GDAC or
[[http://data.nodc.noaa.gov/cgi-bin/nph-dods/ghrsst/]{.underline}](http://data.nodc.noaa.gov/cgi-bin/nph-dods/ghrsst/)
at the LTSRF

## 3.2 FTP

> All GHRSST Level 2 Preprocessed, Level 3 and Level 4 Preprocessed
> Products are available through a 30 day rolling archive at
> GDAC/PO.DAAC through <ftp://podaac.jpl.nasa.gov/pub/GHRSST>. Also
> included is read software for all L2P and L4 products. After 30 days
> data is available through the permanent archive at NODC at
>
> [ftp://data.nodc.noaa.gov/pub/data.nodc/ghrsst/]{.underline}

## 3.3 HTTP

Data may be retrieved directly for the first 30 days from the GDAC at
[http://ghrsst.jpl.nasa.gov](http://ghrsst.jpl.nasa.gov/). After 30 days
data may be retrieved through the LTRSF at http://ghrsst.nodc.noaa.gov/

## 3.4 POET 

> Currently Level 4 data is available through the GDAC/PO.DAAC Ocean
> Earth Science Information Partner Federation (ESIP) Tool (POET)
> ([http://poet.jpl.nasa.gov](http://poet.jpl.nasa.gov/)). This tool
> allows for complete subsetting of all level 4 data in both the
> temporal and spatial domains. As of this writing level 4 data sets
> included in POET are:
>
> OSTIA: Operational Sea Surface Temperature and Sea Ice Analysis
>
> ODYSSEA: Global High Resolution Foundation Sea Surface Temperature
> Analysis
>
> NODC AVHRR OI: National Oceanographic Data Center (NODC) Advanced Very
> High Resolution Radiometer (AVHRR) Optimal Interpolation
>
> NODC AVHRR + AMSRE OI: National Oceanographic Data Center (NODC)
> Advanced Very High Resolution Radiometer (AVHRR) and Advanced
> Microwave Scanning Radiometer-EOS (AMSRE) Optimal Interpolation
>
> Remote Sensing Systems Blended AVHRR + Microwave product
>
> It is anticipated that as GHRSST Level 4 data sets become available
> they will be integrated into the POET tool. Future plans include the
> development of a L2P subsetting capability through the POET interface.
> Other regional products in the Mediterranean and the Baltic Sea are
> available.

# 4.0 Using Data (Confidence Flags and Ancillary Fields) 

## 4.1 Description of how to use confidence flags and/or quality levels

### 4.1.2 MICROWAVE

In the simplified user manual I would recommend that users simply use
the total confidence value. If MWCV is less than 3, then the data should
be thrown out. Advanced users can examine the actual confidence flags or
rejection flags for additional information if they choose.

It might be useful if in the JPL software there was a special question
asked of the user in the netcdf reading routines requesting confidence
values to highlight the use of these confidence values. Unprocessed data
is given a higher value than Bad and Suspect data because if it hasn't
been flagged than it is good data.

**Microwave Proximity confidence value (MWPCV) definitions.**

  ----------- -----------------------------------------------------------------
  **Value**   **Definition**

  1           Bad: Data has been rejected

  2           Suspect: Data that may be contaminated, (any confidence flags
              thrown except DW)

  3           Unprocessed: Data that have not been classified by confidence
              flags. This data should be fine.

  4           Excellent: Data that we think are good
  ----------- -----------------------------------------------------------------

Microwave confidence flags definitions.

  ----- ------------------------------------------------------------------
  Bit   Definition

  0     rain present within 50km and difference from yesterday's OI SST
        greater than 0.6 K

  1     rain present within 100km and difference from yesterday's OI SST
        greater than 0.8 K

  2     ice present within 150 km and difference from yesterday's OI SST
        greater than 0.6 K

  3     difference from yesterday's OI SST greater than 5 K

  4     STD and Mean calculated from yesterday's OI SST from data within
        250 km of pixel. SST at pixel required to be within 3\*STD of mean

  5     land present within 125 km and difference from yesterday's OI SST
        greater than 0.6 K

  6     diurnal warming calculated from model greater than 1 K

  7     diurnal warming calculated from model greater than 0.3 K
  ----- ------------------------------------------------------------------

### 4.1.3 MSG/SEVIRI SST

**Sensor description :**

Meteosat Second Generation (MSG) is a series of spin stabilized
geostationary satellites operated by EUMETSAT. Their subpoint nominal
coordinates are 0N, 0E. MSG2 replaced MSG1 in May 2007. They carry the
Spinning Enhanced Visible and Infrared Imager (SEVIRI) which has 2
visible channels at 0.6 and 0.8 mm , one near IR channel at 1.6 mm and 4
IR channels at 3.9, 8.7, 10.8 and 12 mm. The resolution ranges from 3km
at subpoint to about 4.5 km at 40N 0E and 9 km at 60N 0E.The repeat
cycle is 15minutes. For more details see Schmetz et al 2002.

**SST processing:**

SST processing is done by EUMETSAT through their Ocean and Sea Ice
Satellite Application Facility (OSI SAF) at the Centre de Meteorologie
Spatiale of Meteo-France (MF/CMS) in Lannion (France). They are then
converted into L2P through the MEDSPIRATION chain also implemented at
MF/CMS.

SST is calculated every hour at full satellite resolution; a confidence
level is calculated for each pixel. They are remapped over a regular 0.1
degree resolution grid over the OSI SAF Atlantic domain (100W-45E,
60S-89.9N), then averaged over three hour periods centred on 0100, 0400,
0700... UTC. SEVIRI derived SST are subskin SST calculated via a split
window algorithm and bias corrected against nighttime buoy measurements.
A Saharan Dust Index is derived from the SEVIRI data and used to
mask/correct the SST calculations (since April 2006).

For more details see Le Borgne et al., 2006. A detailed Product User
Manual, validation results and reports are available through
http://[www.osi-saf.org](http://www.osi-saf.org/).

**Format and content :**

The L2P products are full (GDS v1.5 compliant) L2P including SST,
confidence levels and SSES with the following ancillary data: Sea Ice
Fraction (OSI SAF), aerosol optical depth (NAAPS), wind speed (ECMWF),
Surface Solar Irradiance (ECMWF or OSI SAF).

## 4.2 Confidence levels and SSES

The confidence levels are derived on a 5 level scale from 0 (unprocessed
) to 5 (excellent), as described in GDS v1.5. They reflect mainly a
potential contamination by cloudiness. It is recommended not to use the
level 2 (bad) data for quantitative use.

SSES are derived from the Match up Data Base (MDB) over a period of one
year or longer and represents the error statistics (bias and standard
deviation) corresponding to each confidence level. It is recommended to
correct for the SSES bias before use. Note that the SSES always provides
an **error**.

**Contact:**

Through the OSI SAF help desk system, see
http://[www.osi-saf.org](http://www.osi-saf.org/)

References:

Schmetz, J., P. Pili, S. Tjemkes, D. Just,, J. Kerkmann, S. Rota and A.
Ratier, 2002, An introduction to Meteosat Second Generation, Bulletin of
the American Meteorological Society, 977-992.

Le Borgne, P., G.Legendre and A. Marsouin, 2006, Proceedings of the 2006
EUMETSAT Meteorological Satellite data User's Conference, Helsinki,
Finland.

## 4.3 Description of Ancillary Fields 

Each GHRSST L2P netCDF file contains ancillary fields, co-located in
space and time to the L2P locations, that are known to affect the
calculation of SSTs. These ancillary fields include, wind speed,
surface-solar-irradiance, aerosols, and sea ice fraction. These fields
can then be used for flagging purposes or for statistical studies of the
effects of these parameters on the calculation of SSTs. Ancillary fields
are either filled in by the appropriate RDAC or at the GDAC. An
additional field, the DT_analysis, compares the given day's SST with a
reference field or with the previous day's fields. All of these fields
are available as attributes within the netCDF files.

# 5.0 Frequently Asked Questions

1\. What is GHRSST? Group for High Resolution Sea Surface Temperature

2\. What format is the data in? netCDF

3\. How does GHRSST differ from previous SST data sets? Has complete
error characterization, standard netCDF format for all products, the
addition of ancillary fields.

# 6.0 Getting information on GHRSST

<http://www.ghrsst-pp.org/> GHRSST project office

<http://ghrsst.nodc.noaa.gov/> Long Term Stewardship and Reanalysis
Facility

[http://ghrsst.jpl.nasa.gov](http://ghrsst.jpl.nasa.gov/) Global Data
Assembly Center

## 6.1 Google

Doing a search on GHRSST immediately leads you to the GHRSST project
page. Links from there go to GDAC, LTSRF and other GHRSST related
projects.

## 6.2 Wikipedia

Doing a search through wikipedia using GHRSST leads you to a description
of the project and it's purpose.

## 6.3 Peer reviewed publications

## 6.4 Web of Science and Knowledge

http://apps.isiknowledge.com/

## 6.5 User Contact Information

### 6.5.1 Jet Propulsion Laboratory

JPL

> Edward Armstrong

<edward.m.armstrong@jpl.nasa.gov>

> Jorge Vazquez
>
> <jorge.vazquez@jpl.nasa.gov>
>
> Global Data Assembly Center
>
> Physical Oceanography Distributed Active Archive Center
>
> 4800 Oak Grove Dr.
>
> Pasadena, Ca. 91109

### 6.5.2 Bluelink

> Helen Beggs
>
> H.beggs@bom.gov.au
>
> Ocean Satellite Observations Scientist,
>
> Ocean Prediction Group,
>
> Centre for Australian Weather and Climate Research,
>
> Bureau of Meteorology,
>
> 700 Collins St, Melbourne Vic 3000 AUSTRALIA
>
> \<http://www.bom.gov.au/bluelink\>

### 6.5.3 Long Term Stewardship and Reanalysis Facility (LTSRF)

Kenneth S. Casey, Ph.D.

Acting Technical Director

> NOAA National Oceanographic Data Center
>
> 1315 East-West Highway
>
> Silver Spring MD 20910
>
> 301-713-3272 ext 133
>
> Kenneth.casey@noaa.gov
>
> \<http://www.nodc.noaa.gov/SatelliteData\>http://www.nodc.noaa.gov/SatelliteData

# 

# 7.0 APPENDICES

## 7.1 Example read software in IDL

## 

; Copyright 2005, by the California Institute of Technology. ALL RIGHTS

; RESERVED. United States Government Sponsorship acknowledged. Any
commercial

; use must be negotiated with the Office of Technology Transfer at the

; California Institute of Technology.

; \$Id: read_L2P.pro,v 1.4 2008/05/07 18:42:21 ghrsst_mmr Exp \$

; read_L2P.pro e. armstrong Caltech/JPL/NASA

PRO read_L2P, L2P_file, \$, ; input

time, time_atts, \$ ; returned: reference time and attributes

lat, lat_atts, \$ ; latitude and attributes

lon, lon_atts, \$ ; longitude and attributes

sst, sst_atts, \$ ; SST and attributes

sst_dtime, sst_dtime_atts, \$ ; deviation from reference time and
attriubtes

sses_bias, sses_bias_atts, \$ ; SST bias error and attriubtes

sses_sd, sses_sd_atts, \$ ; SST standard dev. error and attributes

dt_analysis, dt_analysis_atts, \$ ; SST/analysis SST difference and
attributes

ssi, ssi_atts, \$ ; surface solar irradiance and attributes

wind, wind_atts, \$ ; wind speed and attributes

aod, aod_atts, \$ ; aersol optical depth and attributes

seaice, seaice_atts, \$ ; sea ice fraction and attributes

ssi_source, ssi_source_atts, \$ ; source of ssi and attributes

wind_source, wind_source_atts, \$ ; soruce of wind speed and attributes

aod_source, aod_source_atts, \$ ; source of aod and attributes

seaice_source, seaice_source_atts, \$ ; source of sea ice and attributs

ssi_sst_dtime, ssi_sst_dtime_atts, \$ ; time difference between ssi and
sst and attributes

wind_sst_dtime, wind_sst_dtime_atts,\$ ; DT between wind and sst and
attributes

aod_sst_dtime, aod_sst_dtime_atts, \$ ; DT between aod and sst and
attributes

sat_zen_ang, sat_zen_ang_atts, \$ ; satellite zenith angle and
attriubtes

reject_flag, reject_flag_atts, \$ ; rejection flag and attributes

conf_flag, conf_flag_atts, \$ ; confidence flag and attributes

proximity_conf, proximity_conf_atts,\$ ; proximity confidence flag and
attributes

global_atts ; global attributes

;\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

; SYNOPSIS:

; Reads (and returns) all the arrays and attributes of a L2P file.

; USAGE:

; IDL\> read_l2p, \'L2P_file.nc\', \.... and all the other args

;\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

;\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

; Open the file and read the data

; arrays. The array attributes

; and global attributes are read

; into a structure.

;\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

print, \'\'

nid = ncdf_open( L2P_file, /nowrite )

; inquire about this file; returns structure

file_info = ncdf_inquire( nid )

; print out the dimensions of this file

for dimid=0, file_info.ndims -1 do begin

ncdf_diminq, nid, dimid, name, size

print, \' \-\--\> dimension \' + name + \' is: \', size

endfor

;
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

; loop over each variable and extract its data and

; metadata

;
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

for varid=0, file_info.nvars-1 do begin

; inquire about the variable; returns structure

var = ncdf_varinq( nid, varid )

print, \'. . . reading variable \', var.name

case var.name of

\'time\': begin

id = ncdf_varid(nid, \'time\')

ncdf_varget, nid, id, time

time_atts = get_array_attributes( nid, id )

break

end

\'lat\': begin

id = ncdf_varid(nid, \'lat\')

ncdf_varget, nid, id, lat

lat_atts = get_array_attributes( nid, id )

break

end

\'lon\': begin

id = ncdf_varid(nid, \'lon\')

ncdf_varget, nid, id, lon

lon_atts = get_array_attributes( nid, id )

break

end

\'sea_surface_temperature\': begin

id = ncdf_varid(nid, \'sea_surface_temperature\')

ncdf_varget, nid, id, sst

sst_atts = get_array_attributes( nid, id )

break

end

\'sst_dtime\': begin

id = ncdf_varid(nid, \'sst_dtime\')

ncdf_varget, nid, id, sst_dtime

sst_dtime_atts = get_array_attributes( nid, id )

break

end

\'SSES_bias_error\': begin

id = ncdf_varid(nid, \'SSES_bias_error\')

ncdf_varget, nid, id, sses_bias

sses_bias_atts = get_array_attributes( nid, id )

break

end

\'SSES_standard_deviation_error\': begin

id = ncdf_varid(nid, \'SSES_standard_deviation_error\')

ncdf_varget, nid, id, sses_sd

sses_sd_atts = get_array_attributes( nid, id )

break

end

\'DT_analysis\': begin

id = ncdf_varid(nid, \'DT_analysis\')

ncdf_varget, nid, id, dt_analysis

dt_analysis_atts = get_array_attributes( nid, id )

break

end

\'surface_solar_irradiance\': begin

id = ncdf_varid(nid, \'surface_solar_irradiance\')

ncdf_varget, nid, id, ssi

ssi_atts = get_array_attributes( nid, id )

break

end

\'wind_speed\': begin

id = ncdf_varid(nid, \'wind_speed\')

ncdf_varget, nid, id, wind

wind_atts = get_array_attributes( nid, id )

break

end

\'sea_ice_fraction\': begin

id = ncdf_varid(nid, \'sea_ice_fraction\')

ncdf_varget, nid, id, seaeice

seaice_atts = get_array_attributes( nid, id )

break

end

\'aerosol_optical_depth\': begin

id = ncdf_varid(nid, \'aerosol_optical_depth\')

ncdf_varget, nid, id, aod

aod_atts = get_array_attributes( nid, id )

break

end

\'satellite_zenith_angle\': begin

id = ncdf_varid(nid, \'satellite_zenith_angle\')

ncdf_varget, nid, id, sat_zen_ang

sat_zen_ang_atts = get_array_attributes( nid, id )

break

end

\'sources_of_ssi\': begin

id = ncdf_varid(nid, \'sources_of_ssi\')

ncdf_varget, nid, id, ssi_source

ssi_source_atts = get_array_attributes( nid, id )

break

end

\'sources_of_wind_speed\': begin

id = ncdf_varid(nid, \'sources_of_wind_speed\')

ncdf_varget, nid, id, wind_source

wind_source_atts = get_array_attributes( nid, id )

break

end

\'sources_of_sea_ice_fraction\': begin

id = ncdf_varid(nid, \'sources_of_sea_ice_fraction\')

ncdf_varget, nid, id, seaice_source

seaice_source_atts = get_array_attributes( nid, id )

break

end

\'sources_of_aod\': begin

id = ncdf_varid(nid, \'sources_of_aod\')

ncdf_varget, nid, id, aod_source

aod_source_atts = get_array_attributes( nid, id )

break

end

\'ssi_dtime_from_sst\': begin

id = ncdf_varid(nid, \'ssi_dtime_from_sst\')

ncdf_varget, nid, id, ssi_sst_dtime

ssi_sst_dtime_atts = get_array_attributes( nid, id )

break

end

\'wind_speed_dtime_from_sst\': begin

id = ncdf_varid(nid, \'wind_speed_dtime_from_sst\')

ncdf_varget, nid, id, wind_sst_dtime

wind_sst_dtime_atts = get_array_attributes( nid, id )

break

end

\'aod_dtime_from_sst\': begin

id = ncdf_varid(nid, \'aod_dtime_from_sst\')

ncdf_varget, nid, id, aod_sst_dtime

aod_sst_dtime_atts = get_array_attributes( nid, id )

break

end

\'rejection_flag\': begin

id = ncdf_varid(nid, \'rejection_flag\')

ncdf_varget, nid, id, reject_flag

reject_flag_atts = get_array_attributes( nid, id )

break

end

\'confidence_flag\': begin

id = ncdf_varid(nid, \'confidence_flag\')

ncdf_varget, nid, id, conf_flag

conf_flag_atts = get_array_attributes( nid, id )

break

end

\'proximity_confidence\': begin

id = ncdf_varid(nid, \'proximity_confidence\')

ncdf_varget, nid, id, proximity_conf

proximity_conf_atts = get_array_attributes( nid, id )

break

end

else: begin

print, \' unknown L2P variable: \', var.name

id = ncdf_varid(nid, var.name)

ncdf_varget, nid, id, new_l2p_array

new_l2p_array_atts = get_array_attributes( nid, id )

end

endcase

endfor

; retrieve the global attributes

print, \'. . . reading global attributes \'

global_atts = get_global_attributes( nid, file_info )

; close the file

ncdf_close, nid

print, \' \--\> done reading L2P \<\-- \'

END

;
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

; returns a structure of COARDS array attributes

;
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

FUNCTION get_array_attributes, nid, array_id

; turn off error messages

ncdf_control, nid, /NOVERBOSE

; returned structure prototype for variable attributes

;array_atts = { long_name:\'\', units:\'\', FillValue:0L,
add_offset:0.0, scale_factor:0.0, \$

; valid_min:0, valid_max:0, coordinates:\'\', source:\'\', comment:\'\',
grid_mapping:\'\', \$

; standard_name:\'\', axis:\'\', positive:\'\' }

; first structure element

array_atts = create_struct(\'dummy\', \'ignore\' )

; inquire about this variable; returns number of attributes

var_info = ncdf_varinq( nid, array_id )

; loop through the attributes and load into a structure

for att_id=0, var_info.natts - 1 do begin

att_name = ncdf_attname( nid, array_id, att_id )

;result = ncdf_attinq( nid, array_id, att_name )

case att_name of

\'long_name\': begin

ncdf_attget, nid, array_id, \'long_name\', long_name

array_atts = create_struct( \'long_name\', string(long_name), array_atts
)

end

\'units\': begin

ncdf_attget, nid, array_id, \'units\', units

array_atts = create_struct( \'units\', string(units), array_atts )

end

\'\_FillValue\': begin

ncdf_attget, nid, array_id, \'\_FillValue\', FillValue

array_atts = create_struct(\'FillValue\', FillValue, array_atts )

end

\'missing_value\': begin

ncdf_attget, nid, array_id, \'missing_value\', FillValue

array_atts = create_struct(\'FillValue\', FillValue, array_atts )

end

\'add_offset\': begin

ncdf_attget, nid, array_id, \'add_offset\', add_offset

array_atts = create_struct(\'add_offset\', add_offset, array_atts )

end

\'scale_factor\': begin

ncdf_attget, nid, array_id, \'scale_factor\', scale_factor

array_atts = create_struct(\'scale_factor\', scale_factor, array_atts )

end

\'valid_min\': begin

ncdf_attget, nid, array_id, \'valid_min\', valid_min

array_atts = create_struct(\'valid_min\', valid_min, array_atts )

end

\'valid_max\': begin

ncdf_attget, nid, array_id, \'valid_max\', valid_max

array_atts = create_struct(\'valid_max\', valid_max, array_atts )

end

\'coordinates\': begin

ncdf_attget, nid, array_id, \'coordinates\', coordinates

array_atts = create_struct(\'coordinates\', string(coordinates),
array_atts )

end

\'source\': begin

ncdf_attget, nid, array_id, \'source\', source

array_atts = create_struct(\'source\', string(source), array_atts )

end

\'comment\': begin

ncdf_attget, nid, array_id, \'comment\', comment

array_atts = create_struct(\'comment\', string(comment), array_atts )

end

\'grid_mapping\': begin

ncdf_attget, nid, array_id, \'grid_mapping\', grid_mapping

array_atts = create_struct(\'grid_mapping\', string(grid_mapping),
array_atts )

end

\'axis\': begin

ncdf_attget, nid, array_id, \'axis\', axis

array_atts = create_struct(\'axis\', string(axis), array_atts )

end

\'standard_name\': begin

ncdf_attget, nid, array_id, \'standard_name\', standard_name

array_atts = create_struct(\'standard_name\', string(standard_name),
array_atts )

end

\'positive\': begin

ncdf_attget, nid, array_id, \'positive\', positive

array_atts = create_struct(\'positive\', string(positive), array_atts )

end

else: begin

print, \' unknown attribute: \', att_name

end

endcase

endfor

return, array_atts

END

;
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

; returns a structure of COARDS GLOBAL attributes

;
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--

FUNCTION get_global_attributes, nid, file_info

; returned structure prototype for GLOBAL attributes

global_atts = { global_attributes, Conventions:\'\', title:\'\',
DSD_entry_id:\'\', references:\'\', institution:\'\', \$

contact:\'\', GDS_version_id:\'\', netcdf_version_id:\'\',
creation_date:\'\', \$

product_version:\'\', history:\'\', platform:\'\', sensor:\'\',
spatial_resolution:\'\', \$

start_date:\'\', start_time:\'\', stop_date:\'\', stop_time:\'\',
northernmost_latitude:0.0, \$

southernmost_latitude:0.0, westernmost_longitude:0.0,
easternmost_longitude:0.0, \$

file_quality_index:0, comment:\'\' }

; loop through the global attributes and load into a structure

for gatt_id=0, file_info.ngatts - 1 do begin

gatt_name = ncdf_attname( nid, gatt_id, /GLOBAL )

case gatt_name of

\'Conventions\': begin

ncdf_attget, nid, \'Conventions\', Conventions, /GLOBAL

global_atts.Conventions = string(Conventions)

end

\'DSD_entry_id\': begin

ncdf_attget, nid, \'DSD_entry_id\', DSD_entry_id, /GLOBAL

global_atts.DSD_entry_id = string(DSD_entry_id)

end

\'title\': begin

ncdf_attget, nid, \'title\', title, /GLOBAL

global_atts.title = string(title)

end

\'references\': begin

ncdf_attget, nid, \'references\', references, /GLOBAL

global_atts.references = string(references)

end

\'institution\': begin

ncdf_attget, nid, \'institution\', institution, /GLOBAL

global_atts.institution = string(institution)

end

\'contact\': begin

ncdf_attget, nid, \'contact\', contact, /GLOBAL

global_atts.contact = string(contact)

end

\'institution\': begin

ncdf_attget, nid, \'institution\', institution, /GLOBAL

global_atts.institution = string(institution)

end

\'GDS_version_id\': begin

ncdf_attget, nid, \'GDS_version_id\', GDS_version_id, /GLOBAL

global_atts.GDS_version_id = string(GDS_version_id)

end

\'netcdf_version_id\': begin

ncdf_attget, nid, \'netcdf_version_id\', netcdf_version_id, /GLOBAL

global_atts.netcdf_version_id = string(netcdf_version_id)

end

\'creation_date\': begin

ncdf_attget, nid, \'creation_date\', creation_date, /GLOBAL

global_atts.creation_date = string(creation_date)

end

\'product_version\': begin

ncdf_attget, nid, \'product_version\', product_version, /GLOBAL

global_atts.product_version = string(product_version)

end

\'history\': begin

ncdf_attget, nid, \'history\', history, /GLOBAL

global_atts.history = string(history)

end

\'platform\': begin

ncdf_attget, nid, \'platform\', platform, /GLOBAL

global_atts.platform = string(platform)

end

\'sensor\': begin

ncdf_attget, nid, \'sensor\', sensor, /GLOBAL

global_atts.sensor = string(sensor)

end

\'spatial_resolution\': begin

ncdf_attget, nid, \'spatial_resolution\', spatial_resolution, /GLOBAL

global_atts.spatial_resolution = string(spatial_resolution)

end

\'start_date\': begin

ncdf_attget, nid, \'start_date\', start_date, /GLOBAL

global_atts.start_date = string(start_date)

end

\'start_time\': begin

ncdf_attget, nid, \'start_time\', start_time, /GLOBAL

global_atts.start_time = string(start_time)

end

\'stop_date\': begin

ncdf_attget, nid, \'stop_date\', stop_date, /GLOBAL

global_atts.stop_date = string(stop_date)

end

\'stop_time\': begin

ncdf_attget, nid, \'stop_time\', stop_time, /GLOBAL

global_atts.stop_time = string(stop_time)

end

\'northernmost_latitude\': begin

ncdf_attget, nid, \'northernmost_latitude\', northernmost_latitude,
/GLOBAL

global_atts.northernmost_latitude = northernmost_latitude

end

\'southernmost_latitude\': begin

ncdf_attget, nid, \'southernmost_latitude\', southernmost_latitude,
/GLOBAL

global_atts.southernmost_latitude = southernmost_latitude

end

\'westernmost_longitude\': begin

ncdf_attget, nid, \'westernmost_longitude\', westernmost_longitude,
/GLOBAL

global_atts.westernmost_longitude = westernmost_longitude

end

\'easternmost_longitude\': begin

ncdf_attget, nid, \'easternmost_longitude\', easternmost_longitude,
/GLOBAL

global_atts.easternmost_longitude = easternmost_longitude

end

\'file_quality_index\': begin

ncdf_attget, nid, \'file_quality_index\', file_quality_index, /GLOBAL

global_atts.file_quality_index = file_quality_index

end

\'comment\': begin

ncdf_attget, nid, \'comment\', comment, /GLOBAL

global_atts.comment = string(comment)

end

else: begin

print, \' unknown attribute: \', gatt_name

end

endcase

endfor

return, global_atts

END

; Copyright 2005, by the California Institute of Technology. ALL RIGHTS\
; RESERVED. United States Government Sponsorship acknowledged. Any
commercial\
; use must be negotiated with the Office of Technology Transfer at the\
; California Institute of Technology.\
\
; \$Id: L2P_driver.pro,v 1.5 2008/05/07 18:51:26 ghrsst_mmr Exp \$\
; L2P_driver.pro e. armstrong Caltech/JPL/NASA\
\
PRO L2P_driver, L2P_file\
\
;
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--\
; SYNOPSIS:\
; Calls read_L2P.pro to read\
; the GHRSST L2P netCDF format.\
; All arrays and their attributes are\
; read into memory.\
\
; USAGE:\
; IDL\> .compile L2P_driver\
; IDL\> .compile read_L2P (may need to compile twice)\
; IDL\> L2P_driver, \<L2P_file\>\
;
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--\
\
if n_params() ne 1 then begin\
usage\
stop\
endif\
\
print, \'\'\
print, \' reading L2P file: \' + L2P_file\
\
; call the file reader\
read_L2P, L2P_file, \$, ; only input\
time, time_atts \$ ; returned: reference time and attributes\
lat, lat_atts, \$ ; latitude and attributes\
lon, lon_atts, \$ ; longitude and attributes\
sst, sst_atts, \$ ; SST and attributes\
sst_dtime, sst_dtime_atts, \$ ; deviation from reference time and
attriubtes\
sses_bias, sses_bias_atts, \$ ; SST bias error and attriubtes\
sses_sd, sses_sd_atts, \$ ; SST standard dev. error and attributes\
dt_analysis, dt_analysis_atts, \$ ; SST/analysis SST difference and
attributes\
ssi, ssi_atts, \$ ; surface solar irradiance and attributes\
wind, wind_atts, \$ ; wind speed and attributes\
aod, aod_atts, \$ ; aersol optical depth and attributes\
seaice, seaice_atts, \$ ; sea ice fraction and attributes\
ssi_source, ssi_source_atts, \$ ; source of ssi and attributes\
wind_source, wind_source_atts, \$ ; soruce of wind speed and attributes\
aod_source, aod_source_atts, \$ ; source of aod and attributes\
seaice_source, seaice_source_atts, \$ ; source of sea ice and attributs\
ssi_sst_dtime, ssi_sst_dtime_atts, \$ ; time difference between ssi and
sst and attributes\
wind_sst_dtime, wind_sst_dtime_atts,\$ ; DT between wind and sst and
attributes\
aod_sst_dtime, aod_sst_dtime_atts, \$ ; DT between aod and sst and
attributes\
sat_zen_ang, sat_zen_ang_atts, \$ ; satellite zenith angle and
attributes\
reject_flag, reject_flag_atts, \$ ; rejection flag and attributes\
conf_flag, conf_flag_atts, \$ ; confidence flag and attributes\
proximity_conf, proximity_conf_atts,\$ ; proximity confidence flag and
attributes\
global_atts ; global attributes\
\
\
;
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--\
; Example of how to use the arrays and\
; and metadata.\
;
\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\--\
\
; find the missing values in the sst array\
missing_values = where( sst eq sst_atts.FillValue, count)\
\
; scale the SST\
sst = sst \* sst_atts.scale_factor + sst_atts.add_offset\
\
; set missing values to back to FillValue value\
if count ne 0 then begin\
sst\[missing_values\] = sst_atts.FillValue\
endif\
\
; print out a few things about this file\
print, \'\'\
print, \' some details of this file . . . \'\
print, \' the northernmost latitude: \',
global_atts.northernmost_latitude\
print, \' the southernmost latitude: \',
global_atts.southernmost_latitude\
print, \' the easternmost longitude: \',
global_atts.easternmost_longitude\
print, \' the westernmost longitude: \',
global_atts.westernmost_longitude\
print, \'\'\
print, \'\--\> example for \', sst_atts.long_name\
print, \'\--\> units are: \', sst_atts.units\
print, \'\--\> scale factor: \', sst_atts.scale_factor\
print, \'\--\> add offset: \', sst_atts.add_offset\
print, \'\--\> missing values are: \', sst_atts.FillValue\
\
lat_size = size(lat) ; determine if 1d or 2d lat/lon array\
if lat_size\[0\] eq 1 then begin\
print, \' AT latitude: \', lat\[100\]\
print, \' AND longitude: \', lon\[100\]\
print, \' SST is: \', sst\[100\]\
endif else begin\
print, \' AT latitude: \', lat\[100,100\]\
print, \' AND longitude: \', lon\[100,100\]\
print, \' SST is: \', sst\[100,100\]\
endelse\
\
print, \' time of first observation is (sec): \', time\[0\]\
\
\
END\
\
PRO usage\
print, \" read L2P netCDF variables and metadata into memory\"\
print, \" USAGE: \"\
print, \" IDL\> L2P_driver, \<L2P_file\>\
print, \'\'\
END

## 7.2 The GHRSST Match-Up Database

### 7.2.1 Overview

The development of GHRSST-PP system has strengthened the need for the
intercomparison of the available satellite sea surface temperature
products and the estimation of the various sensor error statistics,
especially when adressing issues such as sensor merging into analysis
systems. In situ data have proved to be a reliable independant source to
compare these products and sensors to each other. Satellite and in situ
measurements coincident in time (typically less than 6 hours time
difference) and space (typically less than 25 km distance) are refered
as *match-ups* and can be extracted in real or near real-time on a
systematic basis to perform continuous control of the sensors and
retrieval algorithms.

To serve that purpose, a database (MDB) providing satellite to in situ
match-ups was set up in the frame of ESA funded **Medspiration**
project, relying within an integrated framework on Coriolis system (for
the worlwide collection and provision of in situ sea temperature and
salinity data from GTS, Argo,etc\..., http://www.coriolis.eu.org) and
Medspiration data archive (the european node to GHRSST-PP system,
[http://www.medspiration.org](http://www.medspiration.org/)), both
hosted at Ifremer, Brest, France. The strength of having a single source
for in situ data is to ensure that all match-ups are consistent together
since they have been processed in the same manner with the same in situ
data, each of them with the same level of quality and following
consistent control procedures; respective satellite sensor error
statistics can then be estimated with better confidence.

The MDB service currently set up offers to users periodic match-up data
files for each Medspiration GHRSST datasets in netCDF format, as well as
an online extraction interface to perform more constrained queries
(using time/space criteria, selecting the data sources to consider,
using selection filters,..). It can be accessed at the following place :

<http://www.medspiration.org/tools/mdb/>

### 7.2.2 Future plans

The scope of the match-up database has been limited so far to the GHRSST
products delivered by the European DAC (Medspiration project). Future
plans mostly focus on extending this scope to all other data sources
(both satellite and in situ) and adding new high-level functionnalities
to the service :

-   processing and delivering match-ups for all other GHRSST datasets

-   including new sources of in situ measurements (if not handled by
    Coriolis database), which may include for instance in situ
    radiometer data

-   complementing the database with historical match-ups (provided by
    other existing MDBs such as for MODIS, AMSRE, TMI, METOP,
    AVHRR,\....) or additional ancillary information (for better quality
    control or stratification of the MDB)

-   implementing automatic procedures to trigger alarms when anomalies
    or drifting of the satellite sensors are detected by comparison with
    in situ data

-   implementing automatic and independant computation of SSES and
    providing periodically updated values

For more information on MDB content, processign details or data format,
please refer to the MDB user manual appendice.

## 7.3 High Resolution Diagnostic Data Sets (HRDDS)

### 7.3.1 Overview

The GHRSST-PP High Resolution Diagnostic Data Set is an online
interactive archive and database system designed to allow fast and easy
inter-comparison of all types of SST products.

The system features two main components. Firstly, a dedicated web
portal, hosted at the National Oceanography Centre, Southampton (United
Kingdom), that users may perform a host of interactive analysis through
the HR-DDS database to which it is connected. Secondly, a large archive
of GHRSST and other SST subsets that are made available via FTP and
OPeNDAP.

The HR-DDS was initially constructed for the ESA funded MEDSPIRATION
([http://www.medspiration.org](http://www.medspiration.org/)) project,
the European contribution to GHRSST. It has since been expanded to
encompass the entire GHRSST project. It has received additional finding
from the EU MERSEA
([http://www.mersea.eu.org](http://www.mersea.eu.org/)) project and also
from the UK's Met Office through the National Centre for Ocean
Forecasting (NCOF [http://www.ncof.co.uk](http://www.ncof.co.uk/)).

The HR-DDS ingests nearly all GHRSST SST products and many additional
SST products from outside the project. Every data file provided is
analysed to find SST observations at all of approximately 250 *HR-DDS
sites*. These *HR-DDS sites* are geographic regions typically 2° by 2°
is size, located over regions of interesting oceanographic or
atmospheric conditions, areas with known *in situ* observations or
regions representative of typical oceanic conditions. Additionally, many
site are located in Polar Regions to aid validation of SST products in
the difficult conditions prevalent at those latitudes.

Every time an SST product contains an observation at one of these
*HR-DDS sites* and new *HR-DDS granule* is produced. This is a subset of
the original file with only the data for that location. This data is
always interpolated onto a 0.01° by 0.01° degree regular grid through
the nearest neighbour technique. Any absence of observation is
maintained in the new grid. These files maintain the format of the
source file, other that the grid specification as described.

Each of these granules is also analysed at creation to create a
statistical representation of each field that is then entered into the
*HR-DDS database*. These statistics include the mean, median, skew,
kurtosis, standard deviation, maximum and minimum values for the field.
The statistics are calculated for the entire field, and for a smaller
0.05° by 0.05° region known as the centre area (although this region is
not exactly in the centre for each *HR-DDS site* -- typically when that
area my be land). All these statistics are then recomputed only for
pixels of the highest quality level of each product. These statistics
form a broadly representative sample of each *HR-DDS* granule and are
very quick to analyse. At the time of writing the *HR-DDS database*
contains over 300,000,000 statistics from over 2,000,000 *HR-DDS
granules*.

### 7.3.2 The HR-DDS portal

The main feature of the HR-DDS system is the interactive web portal,
which provides many features for the analysis of SST data. The portal is
accessible at the URL http://www.hrdds.net.

The front page of the HR-DDS portal presents a global SST field, usually
obtained from the previous days OSTIA analysis, a GHRSST L4 product.
Superimposed on this image are approximately 250 rectangles. These
represent the location of the *HR-DDS sites*, an example is shown in
Figure .

![](media/image2.png){width="5.759722222222222in"
height="3.2895833333333333in"}

Figure A7.1 The location of the *HR-DDS sites*. This image is taken from
the HR-DDS web portal front page. Red sites indicate the likely presence
of *in situ* observations, white and yellow sites have been added by
special request, purple sites indicate coasts or lakes. Blue sites have
been added for the ocean colour communities.

The user may hold the mouse over any of these sites to see its exact
location and name. Users of the portal may now perform two tasks. They
may select to zoom in to a region by clicking anywhere other than on an
*HR-DDS site*, or they may choose to begin analysing the data at an
*HR-DDS* *site* by clicking on that site.

There is a menu bar to the left of the website that is always available.
This menu bar contains links to this user guide, 'walkthrough'
demonstrations, descriptions of the data within the system, methods of
downloading the data, user registration and configuration options and
much more.

### 7.3.3 Time series analysis

Users may enter the time series analysis pages by clicking on any site
on the front page. They are then presented with a dynamically generated
graph showing the mean SST of every *HR-DDS granule* over that site for
the last 14 days. An example of this type of image is given in Figure .
A detailed and up to date legend is provided by the website.

![](media/image3.png){width="5.759722222222222in" height="2.875in"}

Figure A7.2 An example time series produced by the HR-DDS website. This
is an example for a site in the Western Approaches. A legend is
available on the website, directly below this image. Colour represents
an instrument type, and each shape represents a product type.

Above the plot are six small hyperlinks allowing the user to change the
time frame of the image. Options are to move back or forward by on day,
one month or one year. These are the only controls on the page that **do
not** require the user to hit the 'Select and Plot' button at the bottom
of the page

There are also many other controls the user may employ to modify the
appearance of this plot and also control the data that is included in
the plot. After modifying the value of these fields, the user must hit
the 'Select and Plot' button at the bottom of the page to inform the
website you have finished and wish to view the results. These are
described bellow:

-   **Y-axis minimum.** The user may enter any value into this box,
    which will define the lower limit of the Y-axis of the graph.
    Entering the word 'auto' will instruct the website to automatically
    select an appropriate minimum value. No units should be entered into
    this box, only numerical values or the word 'auto'. To make the
    change user must hit the 'Select and Plot' button at the bottom of
    the page.

-   **Y-axis maximum.** Same as **Y-axis minimum** except it controls
    the maximum value of the plot. **Note:** To reverse the Y-axis,
    simply enter the minimum value you wish into the maximum value box,
    and *vice versa*.

-   **Minimum valid data coverage.** Enter into this box the minimum
    percentage of SST coverage you require of each *granule* in order to
    include it in the plot. For example, to restrict you analysis to
    data with a lower risk of cloud contamination, entre a higher value.

-   **Parameter type.** This is the variable you wish to view on the
    Y-axis. The default parameter is *sea surface temperature*. At the
    time of writing nearly twenty other variables are available to plot,
    although no data source includes every parameter.

-   **Statistical operator.** This defines the statistical value of each
    field you wish to plot, the default is *mean*. Therefore by default
    the *mean sea surface temperature* of each *granule* is shown in an
    unmodified plot.

-   **Coverage and quality.** This option controls whether the statistic
    shown on the plot is derived from the centre area (0.05° by 0.05°)
    or all the area (typically 2° by 2°), and whether the statistic is
    derived from all available observations or just high quality
    observations.

-   **Error estimation.** Some statistics in the *database* have an
    associated error estimate (for example, the
    SSES_standard_deviation_error of the L2P format). By default these
    are represented as horizontal error bars on appropriate points. User
    may disable with feature by selecting *no error estimation* in this
    option list.

-   **Bias correction.** Some statistics in the *database* have an
    associated error correction (for example, the SSES_bias_error of the
    L2P format). By default values are applied to appropriate points.
    User may disable with feature by selecting *no bias correction* in
    this option list.

-   **In situ observations.** Recently the HR-DDS has included *in situ*
    observations of some parameters in the *database*. By default these
    are not displayed, however to view these observations you may select
    *with in situ observations* from this option list.

-   **Select your HRDDS site.** This feature allows you to quickly view
    a plot with the same configuration by with data from a different
    *HR-DDS site*.

-   **Start date.** This defines the date of the earliest data you wish
    to include. By default this will be set to 14 days before the
    current date.

-   **End date.** This selects the date of the latest data you wish to
    include in the plot. By default it is the current date.

-   **Select and Plot.** This activates any change you have made to the
    plot configuration.

Holding the mouse over any of the points on the plot will reveal more
information about that point. The actual Y-axis value is included in
this information along with a description of the sensor system and
instrument used.

From here the user may either elect to produce a *spatial
inter-comparison* of the data for a specific day, view an image of the
field containing the data for which a statistic has been derived or
produce a *multivariate scatter plot*.

To view an image of the data used to produce the point on the plot the
user need only to click on that point. An image of the data is produced
in real time form the *HR-DDS granule* used to generate the statistics.

**Important note:** The *time series analysis* pages show *sea surface
temperature* in degrees Celcius without exception. The data within the
*HR-DDS granule* will however usually be recorded in kelvin.

### 7.3.4 CSV (comma separated value) pages

From the *time series analysis* pages, a user may select to download the
data from which the plot was generated by clicking on 'Data Access' in
the left hand menu and then clicking on 'CSV Data Access'. The user then
view a page containing in CSV format the data used to generate the plot.
This is useful as CSV data may easily be imported into scientific
analysis applications.

For more simplistic analysis, a simple spreadsheet application will
typically be able to read this data. When using a spreadsheet program
with this data is important to remember that the first line of this data
is a header.

The page contains some HTML so it is wise to copy the page from your web
browser to a simple text editor instead of attempting to save the page
from the browser itself. The CSV data contains the following columns
(delimited, of course, by a comma):

-   **Source name.** This is the internal HR-DDS code for the dataset.
    These codes are identical to or closely resemble the GHRSST data
    code. The meaning of each is given in the product description
    section of the *HR-DDS website*.

-   **Value.** This is the numerical value appearing on the Y-axis of
    the *time series analysis* page. **Note.** If the parameter you are
    viewing is *sea surface temperature* the value you download will be
    in Kelvin, not degrees Celsius as shown on the *time series
    analysis* plot. In fact all *sea surface temperatures* returned from
    the website will be given in degrees Celsius with the exception of
    the CSV data. This is due to various user requests.

-   **Observation start time.** This is the observation time of the
    oldest observation in the *HR-DDS granule* from which the point was
    generated

-   **Observation end time.** This is the observation time of the
    youngest observation in the *HR-DDS granule* form which the point
    was generated.

-   **Variable Name.** The name of the parameter in the CSV data, for
    example *sea surface temperature*, or *wind speed*.

-   **Statistical Operator.** The statistical value of the field in the
    CSV data, for example the *mean* or the *standard deviation*.

-   **Quality Level.** The coverage area and quality level of the data
    included in the analysis, denoted by the area first and then the
    quality level. For example *area all* describes data from the entire
    *HR-DDS granule* are at all quality levels.

-   **Type.** The type of product, for example a *swath* satellite
    product or an *analysis* level 4 product.

### 7.3.5 FTP and OPeNDAP access

User may, form the any site on the page, enter the HR-DDS archive by
clicking in 'Data Access' and then either 'OPeNDAP Data Access' or 'FTP
Data Access'.

Users within UK Universities and Natural Environment Research Council
centres should be able to use the *passive* FTP mode. All other users
will have to configure their FTP client to use the *port* FTP mode.
Almost every FTP client will make this change automatically.

Users may also access the FTP archive from the command line by anonymous
FTP by connecting to the server medserve.noc.soton.ac.uk. Most users
(other than those at Natural Environment Research Council centres an
institutions) will probably have to deactivate the FTP *passive* mode to
use the site. Once logged in, the user must type *'passive'* and enter
it. The archive is divided into *data* and *metadata* directories. All
*HR-DDS* granules are located within the *data/hrdds/* directory of the
server. Within this directory, all granules are organised by year, day
of year and finally site code. The OPeNDAP archive is organised in
exactly the same way.

All *HR-DDS* granules are compressed with the bzip2 compression utility.

### 7.3.6 Multivariate scatter plots

Users may, from the *time series analysis* page, select to produce a
multivariate plot. This plot presents the same Y-axis as the time series
plot, but wit the X-axis being replaced by another parameter. By default
this parameter is *wind speed*. The controls for this plot are very
similar to the *time series analysis* plot, with the following
additions, specifically for the X-axis.

-   **X-axis minimum.** The user may enter any value into this box,
    which will define the lower limit of the X-axis of the graph.
    Entering the word 'auto' will instruct the website to automatically
    select an appropriate minimum value. No units should be entered into
    this box, only numerical values or the word 'auto'. To make the
    change user must hit the 'Select and Plot' button at the bottom of
    the page.

-   **X-axis maximum.** Same as **X-axis minimum** except it controls
    the maximum value of the plot. **Note:** To reverse the X-axis,
    simply enter the minimum value you wish into the maximum value box,
    and *vice versa*.

-   **Parameter type.** This is the variable you wish to view on the
    Y-axis. The default parameter is *sea surface temperature*. At the
    time of writing nearly twenty other variables are available to plot,
    although no data source includes every parameter.

-   **Statistical operator.** This defines the statistical value of each
    field you wish to plot, the default is *mean*. Therefore by default
    the *mean sea surface temperature* of each *granule* is shown in an
    unmodified plot.

-   **Coverage and quality.** This option controls whether the statistic
    show on the plot is derived from the centre area (0.05° by 0.05°) or
    all the area (typically 2° by 2°), and whether the statistic is
    derived from all available observations or just high quality
    observations.

An example of a *multivariate scatter plot* is show in Figure A7.1.

![](media/image4.png){width="5.759722222222222in" height="2.875in"}

Figure A7.1 An example of a *multivariate scatter plot* produced by the
HR-DDS website.

There are some important notes with regard to the *multivariate scatter
plots*. Firstly, points are only displayed if the source *HR-DDS
granule* contains both parameters being plotted. For example, as the
OSTIA product contains only SST, it will not appear on the plot.
Secondly, selecting different quality levels for each axis may not
produce sensible results. This is not an error, it is simply a product
of the fact that some ancillary products may not exist in different
*quality* levels.

To active the *multivariate scatter plot* users must click on the
synonymous link next the 'Select and Plot' button on the *time series
analysis* page. Like the *time series analysis* page, users may also
quickly choose to move forward or backwards in time by one day, one
month or one year using the links above the image.

### 7.3.7 Quick look image

By clicking on any point in either a *time series analysis* plot or a
*multivariate scatter plot* the user is presented with a *quick look
image*. When activated form a *time series analysis* plot the users will
observe the website fade into the background and a new virtual window
appear containing the image requested. An example of this is shown in
Figure A7.2.

![](media/image5.png){width="5.752083333333333in"
height="4.292361111111111in"}

Figure A7.2 Screenshot of a *quick look image* produced by clicking on a
point in a *time series analysis* page.

The image is produced dynamically and in real time from the *HR-DDS
granule*. The scale use is calculated form the maximum and minimum
values of that parameter at that *HR-DDS site* for all products for the
last seven days. White areas denote a missing value in the field, for
example as caused by cloud, land, rain or some other event not allowing
a value to exist.

The field show is the field being viewed on the *time series analysis*
plot, or the Y-axis of the *multivariate scatter plot*. The *quick look
image* also shows some information about the point in question. For
example, the sensor and platform name (if there are inappropriate, a
null value is displayed), the name of the original data provided, and a
description of the type of *sea surface temperature* product from which
the value derives.

Users may click on the left half of the image to view the
chronologically previous image available for that parameter at the site.
Similarly the may click on the right half of the image to view the
chronologically next image. They may also click on the 'CLOSE X' button,
or press the 'esc' key to return to the *time series analysis* or
*multivariate scatter plot* page from which they came.

### 7.3.8 Spatial comparison page

From the *quick look image* of the *time series analysis* plot there is
a link allowing users to enter the *spatial comparison page*. In this
page the *sea surface temperature* of all the *HR-DDS granules* at that
site for that data are show. The minimum coverage value is taken from
the *time series analysis* page. An example of this is shown in Figure
A7.3.

![](media/image6.png){width="5.76875in" height="4.445833333333334in"}

Figure A7.3 An example of a spatial comparison page.

The following controls are available on the *spatial comparison page*,
all of which require the user to click on the 'Select and Plot' button
in order to active:

-   **Maximum.** This value controls the maximum value of the colour
    scale for all the images on the *spatial comparison page*. Entering
    the word 'auto' will require the HR-RRD website to select an
    appropriate value automatically.

-   **Minimum.** This value controls the minimum value of the colour
    scale for all the images on the *spatial comparison page*. Entering
    the word 'auto' will require the HR-RRD website to select an
    appropriate value automatically.

-   **Minimum coverage percentage.** The minimum percentage of area
    covered by the viewing parameter in order to be displayed on the
    page.

Additionally, before the array of images, there are links to move the
data of the displayed either backward of forwards by one day, one month
or one year.

Each image shows a colour scale and a title. The title indicated the
GHRSST / HR-DDS code of the source data, and also the start time of the
granule in UTC. By clicking on any of the images the user may view
anther *quick look image*, or zoomed image of the field. From this
*quick look image* there is a link to the *anomaly analysis page* for
that image.

### 7.3.9 Anomaly analysis page

The anomaly analysis page shows a detailed comparison of the image
selected to all the other data available at that site for that day. The
image selected is the one that was clicked on in order to enter this
page. The page consists of four columns of images as exemplified by

![](media/image7.png){width="5.761111111111111in"
height="4.475in"}Figure 4 An Figure A7.6 Example of an *anomaly analysis
page*.

The first (left) column shows the images that are being compared to the
selected image. If the user holds the mouse over one of these images the
mean and standard deviation of the observations in that image are shown
as a popup. The user may also click on the image to reveal a zoomed
*quick look image*, the user may click on the right side of this image
to view the image to which this image will be compared to.

The second column shows the histogram of the differences between the
image in the first column and the image selected form the *spatial
comparison page*. This histogram is normalised on the Y-axis. Holding
the mouse over the histogram will reveal the mean, standard deviation
and mean to variance ratio of the differences of the two data sets.
Clicking in the histogram will display a larger version of the
histogram. The maximum and minimum difference the histogram shows is set
to +3 and -3 respectively.

The third column shows the actual difference between the fields. The
minimum and maximum difference is set to -1.5 and +1.5 respectively. The
image shown is the data in the first column less the data selected from
the *spatial comparison page*. Holding the mouse over the image will
reveal the mean, standard deviation and mean to variance ratio of the
differences of the two data sets. Clicking on the image will open a new
*quick look image* virtual window. The user may click on the right hand
side of that image to reverse the colour scale of the zoomed difference
plot.

The forth (right) column shows the X Y scatter plot of the differences
between the two datasets. Holding the mouse over the image will show the
correlation coefficient of the two datasets.

You may choose to modify the minimum valid coverage percentage value for
the *anomaly analysis page* by entering a different value into the
appropriate box at the top of the page. To activate the change the user
must click on the 'Select and Plot' button.

The user may download an image of the data to which all the other
datasets are being compared by clicking on the link at the top of the
page just under the *minimum valid coverage percentage* box.

### 7.3.10 Registered user services

Users may register for additional services by selecting 'Users' and then
register from the menu on the left side of the web site. Follow the
instructions on the page to register.

Registered users have access to many additional features on the HR-DDS
website. The registered user homepage is similar to the normal front
page of the HR-DDS website, but with a number of configurable options
and additional links.

Below the site selection map are three links which link to the last
*time series analysis*, *spatial comparison page* and *anomaly analysis
page* viewed by the user. These links are automatically updated by the
HR-DDS system every time a new page is viewed.

There are also several options for configuring the way plots are
produced by the HR-DDS website. Users may define the following default
parameters:

-   To enable or disable the application of bias estimates on the *time
    series analysis* plots

-   To enable or disable the display of vertical error bars on the *time
    serried analysis* plots

-   The default coverage and quality levels shown on *time series
    analysis* plots.

-   The number of days to plot in a *time series analysis* plot.

-   The minimum valid data percentage required in order to include data
    from a particular *HR-DDS granule*.

To record these values the user must click on the 'Change and Store'
button of their home page. All these configurable default parameters are
overridden when a user changes them on an actual plot.

Users must register via the 'Users' and 'Register' tab of the left hand
menu. Users should follow the up-to-date instructions on the web site in
order to register correctly.

### 7.3.11 MyDDSettes

MyDDSettes are dynamically generated bookmarks stored on the HR-DDS
server, which point to a *time series analysis*, *multivariate scatter
plot*, *spatial comparison page* or *anomaly analysis page*. Registered
users will be able to create these MyDDSettes by clinking on the link at
the bottom of the page. Only logged in registered users will be able to
view this link.

To create a MyDDSette, users click on this link are then enter a brief
title and description of the page they are selecting to record.

These may be reviewed, accessed and deleted form the user's home page on
the HR-DDS website, bellow the plot configuration section. Selecting
'Home' and then 'My HR-DDS' from the menu on the right allows users to
access this home page. Users must have previously logged by clicking on
the 'Users' and 'Log in' section of the left hand menu.

The MyDDSettes are listed with the following information:

-   **Title.** The title given to the MyDDSette at the time of creation.

-   **Description.** This is the description of the MyDDSettes given at
    the time of creation.

-   **Type.** The type of data plot recorded in the MyDDSette, e.g. a
    *time series analysis*.

-   **Site code.** The HR-DS code for the *HR-DDS site* that the
    MyDDSette referred to.

-   **Delete.** Users may click on this link to remove the MyDDSette

### 7.3.12 Reporting bugs and suggesting changes

Users (who do not have to be registered) may report a bug or problem
with any page by selecting 'Help' and then 'Report Bug' form the left
hand menu. Users may enter a description of the problem but **DO NOT**
have to report what page the error occurred on, that has already been
recorded by the HR-DDS site.

Users may also suggest a change (or the addition of a feature) on any
page by selecting 'Help' and 'Suggest a change' from the left hand menu
on the website Users **DO NOT** need to not describe the page they are
referring to, that has already been recorded by the HR-DDS system

### 7.3.13 Accessibility options

In accordance with European Law the HR-DDS website may be forced to use
larger bolder fonts by the user, for reasons of impaired vision. This
option is available form the 'Help' section of the left hand menu by
clicking on the 'Larger Text' section.

### 7.3.14 HR-DDS file format

All *HR-DDS granules* are produced in netCDF format and are CF-1.0
compliant. When data are supplied that are not consistent with the
GHRSST data specifications, the HR-DDS system converts these files into
a pseudo GHRSST format. The output *HR-DDS granule* is extremely similar
(or identical) to an *HR-DDS* granule form a GHRSST source.

See the GHRSST product user manual for an exact description of the
GHTSST formats.

The *HR-DDS granules* are a subset of the data from which they were
generated. As such they usually maintain the format of the original data
file with the exception of the grid, which is always 0.01° by 0.01° in
resolution and of a regular cylindrical projection.

GHRSST compliant L2P, L3P and L4 products (and their associated Core
products) maintain almost the exact format of their original data, with
the exception of changes in attributes due to the smaller geographical
area of the data. The GHRSST example software used to read GRIDDED L2P
files will be able to read *HR-DDS granules*.

Files that contain a small number of multiple time frames are split into
separate *HR-DDS granules*. For example, the REMSS AMSRE L2PCore product
contains one layer of data for ascending orbits and another layer for
descending orbits. The HR-DDS system will produce two distinct *HR-DDS
granules* at most sites in this instance, one for each layer. This is
useful as the observations are typically 12 hours apart.

Files from the CORIOLIS *in situ* data set may have essentially one
layer for each observation, in this case the HR-DDS system splits data
up into 1 hour sections and produced an *HR-DDS* granule for each of
these sections. This allows the diurnal signal to be recorded.
Additionally, these data are converted into a pseudo L2PCore format by
the *HR-DDS system*. Internally, the system regards them as AVHRR-GAC
compliant data.

Non-compliant analysis datasets are converted into a pseudo GHRSST L4
format prior to processing. The output *HR-DDS granule* represents this
change.

### 7.3.15 HR-DDS file name convention

The HR-DDS filename convention is as follows:

HRDDS-\<data\>T\<time\>Z-\<product_code\>-\<RDAC\>-\<site_code\>-\<site_name\>-\<HRDDS_software_version\>.nc.bz2

Where:

-   **\<data\>** is a YYYYMMSS format data (e.g. 20010101 for 1^st^
    January 2001)

-   **\<time\>** is a HHMMSS format time string (e.g. 060000 for 6AM --
    all times are in UTC)

-   **\<product_code\>** is the GHRSSR code for that product (e.g.
    SEVIRI_SST for data from the EUMETSAT SEVIRI instrument)

-   **\<RDAC**\> is the GHRSST (or other) data provider (e.g. EUR for
    the MEDSPIRATION project)

-   **\<site_code\>** is the code of the *HR-DDS site* (e.g. mfr002 for
    the Gulf of Lion MeteoFrance buoy site)

-   **\<site_name\>** is the name of the *HR-DDS site* (e.g.
    UKMO_Celtic_Sea_62081, if at the end of the site name there is a 5
    digit numerical code this may be interpreted as the WMO ID of an *in
    situ* observing station located at the centre of the *HR-DDS site*.)

-   **\<HRDDS_software_version\>** is the version of the HR-DDS software
    used to generate the *HR-DDS granule*.

The following is an example of a valid *HR-DDS granule* name:

HRDDS-20080510T131900Z-NAR18_SST-EUR-ukm002-UKMO_Celtic_Sea_62081-v3.nc.bz2.

### 7.3.16 FAQ

1\) Where can I get a more detailed description of data formats?

Answer: The HR-DDS data formats are compliant with the GHRSST format
specification. See the documentation section of the GHRSST website for
more information ([http://www.ghrsst-pp.org](http://www.ghrsst-pp.org/))

2\) What products are included in the HR-DDS?

Answer: A complete product description list is available at the HR-DDS
website under the 'Document' section of the left hand menu

3\) How can I suggest a data source or a site?

Answer: We can add a site in under a minute, and data will populate it
instantly. Although at the moment we cannot guarantee when historical
data will be added to the site. Email Dave Poulter at <djsp@soton.ac.uk>
and suggest a site! To add a data source takes a bit more time, in the
order of days, but feel free to email and request it!

4\) Where can I get regular updates?

Answer: The HR-DDS provides regular updates via RSS, use your browser to
subscribe form any page on the HR-DDS website.

# 8.0 SST definitions

As SST is not a simple measurement defined at one depth, the following
definitions have been put together for the GHRSST project.

-   **The Interface SST (SSTint)**

> SSTint is a theoretical temperature at the precise air-sea interface.
> It represents the hypothetical temperature of the topmost layer of the
> ocean water and could be thought of as an even mix of water and air
> molecules. SSTint is of no practical use because it cannot be measured
> using current technology.

-   **The Skin SST (SSTskin)**

> SSTskin is defined as the radiometric skin temperature measured by an
> infrared radiometer operating in the 10-12 µm spectral waveband. As
> such, it represents the actual temperature of the water at a depth of
> approximately 10-20 µm. This definition is chosen for consistency with
> the majority of infrared satellite and ship mounted radiometer
> measurements. SSTskin measurements are subject to a large potential
> diurnal cycle including cool skin layer effects (especially at night
> under clear skies and low wind speed conditions) and warm layer
> effects in the daytime (not shown in Figure 1). SSTskin will be
> similar to the red 1mm SSTdepth approximation shown in Figure 2.

![](media/image8.png){width="5.631944444444445in"
height="3.4722222222222223in"}

Figure A8.1 Schematic diagram showing (a) idealised night-time vertical
temperature deviations from SSTfnd and (b) idealised day-time vertical
temperature deviations from SSTfnd in the upper ocean.

-   **The subskin SST (SSTsubskin)**

> SSTsubskin represents the temperature at the base of the thermal skin
> layer. The difference between SSTint and SSTsubskin is related to the
> net flux of heat through the thermal skin layer. For practical
> purposes, SSTsubskin can be well approximated to the measurement of
> surface temperature by a microwave radiometer operating in the 6-11
> GHz frequency range, but the relationship is neither direct nor
> invariant to changing physical conditions or to the specific geometry
> of the microwave measurements. SSTskin will be similar to the red 1mm
> SSTdepth approximation shown in Figure 2.

-   **The sea temperature at depth (SSTdepth)**

> All measurements of water temperature beneath the SSTsubskin are
> obtained from a wide variety of sensors such as drifting buoys having
> single temperature sensors attached to their hull, moored buoys that
> sometimes include deep thermistor chains at depths ranging from a few
> meters to a few thousand meters, thermosalinograph (TSG) systems
> aboard ships recording at a fixed depth while the vessel is underway,
> Conductivity Temperature and Depth (CTD) systems providing detailed
> vertical profiles of the thermohaline structure used during
> hydrographic surveys and to considerable depths of several thousand
> meters and various expendable bathythermograph systems (XBT). In all
> cases, these temperature observations are distinct from those obtained
> using remote sensing techniques and measurements at a given depth
> arguably should be referred to as 'sea temperature' (ST) qualified by
> a depth in meters rather than sea ***surface*** temperatures. The
> situation is complicated further when one considers ocean model
> outputs for which the SST may be the mean SST over a layer of the
> ocean several tens of meters thick.
>
> SSTdepth or SST(z) is the terminology adopted by GHRSST-PP to
> represent an *in situ* measurement near the surface of the ocean that
> is typically reported simply as SST or \"bulk\" SST. For example
> SST~6m~ would refer to an SST measurement made at a depth of 6m.
> Figure 2 demonstrated the need for introducing the new terminology in
> the upper 5m of the ocean surface as SSTdepth has magnitude and phase
> differences depending on the precise depth. Without a clear statement
> of the precise depth at which the SST measurement was made, and the
> circumstances surrounding the measurement, such a sample lacks the
> information needed for comparison with, or validation of
> satellite-derived estimates of SST using other data sources. The
> terminology has been introduced to encourage the reporting of depth
> (z) along with the temperature.

-   **The diurnal cycle/variation of SST (DV)**

> A diurnal cycle refers to changes in vertical and horizontal
> distribution of SST throughout a 24 hour period and thus includes warm
> stratified layers ***and*** cool skin effects. Cool skin effects are
> typically more pronounced at night due to radiative cooling of the sea
> surface but may also occur during the day when the wind is light
> following a significant rainfall that may leave a cool freshwater
> layer on the surface of the ocean.
>
> Warm layer effects are associated with environmental conditions
> characterised by low wind speed and strong insolation. A warm layer
> readily forms under such conditions effectively decoupling the surface
> layers (typically 0.1-3m deep) from the water beneath.

-   **The Foundation SST (SSTfnd)**

> The **foundation SST, SSTfnd**, is defined as the temperature of the
> water column free of diurnal temperature variability or equal to the
> SSTsubskin in the absence of any diurnal signal. It is named to
> indicate that it is the foundation temperature from which the growth
> of the diurnal thermocline develops each day. SSTfnd provides a
> connection with historical "bulk" SST measurements typically used as
> representative of the oceanic mixed layer temperature. This definition
> was adopted by GHRSST-PP at the Third GHRSST-PP Workshop (Donlon,
> 2003b) to provide a more precise, well-defined quantity than previous
> loosely defined "bulk" temperature quantities and consequently, a
> better representation of the mixed layer temperature. The SSTfnd
> product provides an SST that is free of any diurnal variations
> (daytime warming or nocturnal cooling). In general, SSTfnd will be
> similar to a night time minimum or pre-dawn value at depths of \~1-5
> m, but some differences could exist. Only in situ contact thermometry
> is able to measure SSTfnd. SSTfnd cannot be directly measured using
> either microwave or infrared satellite instruments. Analysis
> procedures must be used to estimate the SSTfnd from radiometric
> measurements of SSTskin and SSTsubskin.

# 9.0 RDACs, GDAC, and the LTSRF

For distribution of the GHRSST --PP a distributed data system was setup
in which the data processing operations that are necessary to generate
and distribute high resolution SST data sets having global coverage are
shared by an international group of Regional Data Assembly Centers
(RDACs). RDACs ingest, quality control and merge existing satellite and
*in situ* SST data sources that are then used together to generate
quality-controlled SST data products to the same specification (called
L2P products), in real-time. The RDACs also may generate Level 3 (L3)
and Level 4 (L4) products. RDAC data products are then assembled
together at Global Data Analysis Centers (GDAC) where they are
integrated, catalogued, and served to users for 30 days. After 30 days,
the data are all sent to the Long Term Stewardship and Reanalysis
Facility (LTSRF), where they are archived, documented, and served in
perpetuity. For a schematic showing the relationship between the RDACS,
GDAC, and LTSRF, see Figure 3.

## 9. 1 RDACs 

GHRSST-PP RDAC centers must implement data processing procedures that
account for specific aspects of regional coverage input data products
(e.g., geostationary imagers). RDAC must also provide additional data
products and services to satisfy regional user requirements (e.g.,
regionally specific analyzed data products or ultra-high resolution data
products) that will require research and development of new analysis,
quality control, and data provision procedures. GHRSST-PP global and
regional coverage SST data products are now produced by GHRSST-PP RDACs
in Australia, Japan, the USA and Europe.

## 9. 2 GDAC

RDAC SST Products are passed in near real-time to operational GHRSST-PP
GDAC Global Data Assembly Centers (GDACs) where the RDAC products are
integrated together and served to the global application community.
GDACs play an essential role in quality control and data management. See
Figure A9.1 for the relationship between the RDACs and the GDAC.

## 9. 3 LTSRF 

The GHRSST Long Term Stewardship and Reanalysis Facility (LTSRF) is
maintained at NOAA's National Oceanographic Data Center (NODC), in
Silver Spring, Maryland, USA. The LTSRF receives all data produced by
GHRSST and submitted to the GDAC. After 30 days, the data are sent from
the GDAC to the NODC LTSRF, where final metadata records are completed
and the data maintained in the

![](media/image9.pct){width="6.0125in" height="4.684027777777778in"}

Figure A9.1: Shows the relationship between Regional Data Assembly
Centers (RDACs), the Global Data Assembly Center (GDAC), and the Long
Term Stewardship and Reanalysis Facility (LTSRF)

# 10.0 netCDF Structure

## 10.1 Why use netCDF?

The GHRSST-PP Science Team chose netCDF in preference to a custom binary
format as this had already been adopted for the Data Sharing Pilot
project within GODAE. While custom binary formats have the advantage of
minimal size and fast I/O, they tend to suffer from documentation and
portability problems. In contrast, netCDF files are self describing -
meaning that software packages can directly read the data and determine
its structure, the variable names and essential metadata such as the
units. The self-describing aspect of netCDF file format means that the
information needed to ensure accurate work by reducing the incidence of
read errors is available with the data itself. netCDF files and be read
and generated using a variety of different languages including Fortran,
C/C++, JAVA or PERL. Most importantly, data visualisation and analysis
packages (e.g. FERRET, IDL, MATLAB) can directly read netCDF files.
Although there is an initial learning curve for users new to netCDF, the
high efficiency when reading netCDF files and ability to store and
access multiple data means that ultimately more time for analysing data
and addressing the application of GHRSST-PP data products rather than
coding interfaces to a whole series of custom binary formats (as is
currently the case). Finally, netCDF is a preferred format for the Live
Access Server (LAS) and OPeNDAP systems that provide easy on-line access
to data and real-time data visualisation.

In summary, the advantages of netCDF files are:

-   NetCDF is used extensively in the atmospheric and oceanic science
    communities.

-   NetCDF is a portable self-describing binary data format.

-   NetCDF is network-transparent, meaning that it can be accessed by
    computers that store integers, characters and floating-point numbers
    in different ways.

-   NetCDF provides direct-access: a small subset of a large dataset may
    be accessed efficiently, without first reading through all the
    preceding data.

-   NetCDF is appendable: data can be appended to a netCDF dataset along
    one dimension without copying the dataset or redefining its
    structure.

-   NetCDF datasets can be read and written in a number of languages,
    these include C, C++, FORTRAN, IDL, Python, Perl, and Java.

-   The different language implementations are freely available from the
    UNIDATA ftp area (<ftp://ftp.unidata.ucar.edu/pub/netcdf/>) or from
    other mirror sites
    (<http://www.unidata.ucar.edu/packages/netcdf/mirrors.html>) .

-   Several graphics packages support netCDF input, making it very easy
    to display and analyse netCDF datasets. For instance FERRET
    (<http://ferret.wrc.noaa.gov/Ferret/>) and CDAT
    (<http://esg.llnl.gov/cdat/>) provide both command line and
    graphical user interfaces for displaying and analysing gridded data.

-   NetCDF is completely and methodically documented in UNIDATA\'s
    NetCDF User\'s Guide
    (<http://www.unidata.ucar.edu/packages/netcdf/guide.txn_toc.html>) .

-   Several groups have defined conventions
    (<http://www.unidata.ucar.edu/packages/netcdf/conventions.html>) for
    netCDF files, to enable the exchange of data. GHRSST-PP has adopted
    the Climate and Forecasting (CF) conventions
    (<http://badc.nerc.ac.uk/help/formats/netcdf/index_cf.html>) for
    netCDF data.

## 10.2 NetCDF and CF conventions

Climate and Forecast (CF) metadata conventions are guidelines and
recommendations as to where to put information within a netCDF file, and
they provide advice as to what type of information you might want to
include. CF conventions allow the creator of the dataset to include
information about the data and the dataset itself (metadata) in a
structured way, which makes it easier for other users to retrieve the
information. We have more information and some examples of CF
conventions (<http://badc.nerc.ac.uk/help/formats/netcdf/index_cf.html>)
as they are used in GHRSST-PP datasets. The global attributes describe
the more general properties and origins of the dataset.

## 10.3 What\'s in a netCDF file?

A very simple example of a netCDF file with CF conventions applied is
available at
<http://badc.nerc.ac.uk/help/formats/netcdf/nc_example.html> . A netCDF
dataset (the filename ends in .nc) is made up of three basic components:

-   variables

-   dimensions

-   attributes

The variables store the actual data, the dimensions give the relevant
dimension information for the variables, and the attributes provide
auxiliary information about the variables or the dataset itself. You can
study the example netCDF file and see more details of the components in
a netCDF dataset. The global attributes can also be added to the netCDF
file, following CF conventions.

## 10.4 Reading and writing netCDF

The popularity of netCDF stems from its portability and relative ease of
use. Although it is a binary data format the netCDF distribution comes
complete with the ncdump utility which produces an ASCII dump of the
dataset and thereby provides a quick-look facility. You can also
generate netCDF files from ASCII data files using the ncgen utility (see
<http://badc.nerc.ac.uk/help/formats/netcdf/nc_utilities.html#ncgen>).
netCDF datasets are commonly written and read using library routines.
The library routines are sensibly named and relatively consistently
named across the different language implementations.

## 10.5 netCDF resources

-   The main netCDF pages including downloads of netCDF code libraries
    and documentation and can be found at the UNIDATA site at
    <http://my.unidata.ucar.edu/content/software/netcdf/index.html>

-   Useful help on installing netCDF libraries and utilities can be
    found at
    <http://badc.nerc.ac.uk/help/formats/netcdf/nc_utilities.html>

-   A variety of low level example programs (IDL, C, FORTRAN) are
    available to read netCDF files at
    <http://www-c4.ucsd.edu/~cids/software/visual.html>.

-   A large number of applications Software for Manipulating or
    Displaying NetCDF Data are available from
    <http://www.unidata.ucar.edu/packages/netcdf/utilities.html>

-   A detailed FAQ for netCDF can be found at
    <http://my.unidata.ucar.edu/content/software/netcdf/docs/faq.html>

# 11.0 MMR (Master Metadata Repository and search capability)

Each data file or granule consists of two different data files, a
satellite data in netCDF, and a XML-based metadata file. The granule
metadata record, known as the File Record (FR) contains XML tags that
adhere broadly to the NASA Directory Interchange Format (DIF) format and
describe relevant information such as time and geolocation. An
additional XML metadata record known as the Data Set Descriptor (DSD)
contains product summary information that is created once and updated on
an as need basis. Together these metadata records reside in a relational
database known as the Master Metadata Repository (MMR) that allows for
search and discovery of all GHRSST products including those that do not
immediately reside at the GDAC. A search capability, based on the MMR
has been developed and is accessible through the GDAC interface. The MMR
can be accessed from the GDAC at home page at http://ghrsst.jpl.nasa.gov

![](media/image10.png){width="6.313888888888889in"
height="8.171527777777778in"}

##