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Journal for accession number: 0058704
Created on:                    2009-10-14 19:32:59 UTC
By:                            Automated Ingest Agent

Source: Group for High Resolution Sea Surface Temperature (GHRSST) Data

These data were submitted for archive to the NODC as part of GHRSST (the
Group for High Resolution Sea Surface Temperature, formerly known as the
Global Ocean Data Assimilation Experiment (GODAE) High Resolution Sea
Surface Temperature Pilot Project, GHRSST-PP). GHRSST maintains an
internationally distributed operational system that delivers global coverage
high-resolution (better than 10 km and ~6 hourly) near-real time SST data
products and delayed mode climate data record SST products.  GHRSST is based
on a global task-sharing system in which the data processing operations are
shared by Regional Data Assembly Centres (RDACs), Global Data Assembly
Centres (GDACs), and a Long Term Stewardship and Reanalysis Facility (LTSRF,
maintained by NODC). The RDACs ingest, quality control and merge existing
satellite and in situ SST data sources that are then merged together to
generate regional coverage SST data products having the same netCDF format
specification (called L2P products), in real-time. RDACs also produce
gridded Level 3 (L3) and gap-free Level 4 (L4) analysis products, all of
which are then assembled together at the GDAC.  For a complete description
of GHRSST including data processing and metadata specifications, please
refer to: The Recommended GHRSST-PP Data Processing Specification GDS
(Version 1 revision 1.5), GHRSST-PP Report Number 17, compiled by Craig
Donlon and the GHRSST Science Team, Published by the International GHRSST
Project Office, Met Office, Fitzroy Road, Exeter, EX3 1PB, United Kingdom,
downloadable from the References section of the GHRSST site at:
http://www.ghrsst-pp.org/. (Note that in June 2009 the GHRSST Science Team
will be releasing a new Version 2 of the GHRSST Data Specification). The
role of the NODC within this international project is to serve as the long
term stewardship center where reprocessing efforts to create climate-quality
SST products are coordinated internationally, and where all GHRSST data are
made available in perpetuity.

GHRSST data are received daily by the NODC 30 days after observation (prior
to 30 days they are available through the GDAC interface) through an
automated procedure made possible largely by the formalized procedures
developed within GHRSST, especially those pertaining to data management,
metadata, and file naming conventions.  The basic strategy is to bring in
data files and corresponding FGDC metadata in XML format on a daily basis,
then use a combination of static information, information from the
filenames, information from within the XML metadata records, and information
generated by the NODC archive system to automatically create an ATDB entry
and accession for each logical grouping of data (there are currently nearly
30 product groupings each day) and then move the relevant data files (there
may be several per accession) and FGDC record into the NODC archive file
systems.  On a routine basis, an http/ftp/OPeNDAP hierarchy is then
constructed of symbolic links pointing to the data and metadata residing in
the formal NODC archive file system.

The GHRSST data streams consist of three types of data and metadata.  The
three types of data managed using the procedures documented here make up the
core of the GHRSST system. These data types, in netCDF format, are:

Level 2 Preprocessed (L2P)
----------------------------------
Individual satellite sensor observations processed into geophysical units
(SST in degrees C) and formatted according to the GHRSST-PP Data Processing
Specifications (GDS v1.5, GHRSST/17) or more recent versions of the GDS.
L2P data contain SST derived from Level 1 source data (which are outside of
the scope of GHRSST) at the same resolution and location as the Level 1
data, typically in a satellite projection with geographic information.
These data form the fundamental basis for higher-level derived GHRSST
products and include, importantly, extensive ancillary data and uncertainty
estimates.

Level 3 (L3)
---------------
These data are Level 2 variables mapped on a defined grid with reduced
GHRSST requirements for ancillary data. Uncertainty estimates are still
mandatory. The reduced requirements for ancillary data help distinguish L3
GHRSST from L2 GHRSST. L3 GHRSST products include un-collated data that
represent a simple remapping of L2 GHRSST data granules to a space grid
without combining any observations from overlapping orbits, collated data
that combine observations from a single instrument into a space-time grid,
and multi-sensor super-collated data that combine observations from a
multiple instruments into a space-time grid.  Note that L3 GHRSST products
do not use analysis or interpolation procedures to fill all gaps where no
observations are available.

Level 4 (L4)
---------------
These are data sets created from the analysis of lower level data that
results in gridded, gap-free products.  SST data generated from multiple
sources of satellite data using optimal interpolation are an example of L4
GHRSST products.

L2P, L3, and L4 data are stored in netCDF format following the procedures
detailed in the GDS.  The netCDF files are compressed using gzip or bzip2
compression and can be decompressed with freely-available software (e.g.,
http://www.bzip.org/).

Summary of GHRSST data management structure:

1. Data processing is managed by a distributed system with international
   partners at Regional Data Assembly Centers (RDACs) around the world.

2. The RDACs generate data and GCMD-DIF style metadata for L2P, L3, and L4
   products.

3. All RDAC data streams are sent first to the Global Data Assembly Center
   (GDAC) at the NASA JPL/Caltech Physical Oceanography Distributed Active
   Archive Center (PO.DAAC). The PO.DAAC (http:/ghrsst.jpl.nasa.gov/),
   provides critical data management functions and user access to these
   real-time data. The PO.DAAC holds the data in a 30 day rolling store, and
   constructs an XML-formatted FGDC-compliant metadata record for each
   logical grouping of data (an NODC "Accession" or Archival Information
   Package) based on the GCMD-DIF style metadata mandated as part of the
   GHRSST system.

4. The PO.DAAC GDAC system makes these data available to NODC 30 days after
   observation.

These data may be retrieved from the NODC via several mechanisms at:

1. NODC Ocean Archive System: http://www.nodc.noaa.gov/search/prod/
2. HTTP Server: http://data.nodc.noaa.gov/ghrsst
3. FTP Server: ftp://data.nodc.noaa.gov/pub/data.nodc/ghrsst
4. OPeNDAP Server: http://data.nodc.noaa.gov/cgi-bin/nph-dods/ghrsst

See the NODC GHRSST Web site: http://ghrsst.nodc.noaa.gov for more
information.

Files:

L4/GLOB/NAVO/K10_SST/2009/254/FGDC-20090911-NAVO-L4HR1m-GLOB-v01-K10_SST.xml -
   FGDC metadata record describing the following data files in this
   accession:

20090911-NAVO-L4HR1m-GLOB-v01-fv01_0-K10_SST.nc.bz2
FR-20090911-NAVO-L4HR1m-GLOB-v01-fv01_0-K10_SST.xml

NODC updates to metadata:

1.1 Citation 8.4 Title: appended " for 2009-09-11 (NODC Accession 0058704)"
1.5.1 Bounding Coordinates: calculated by finding the maximum and
  minimum range domains for the Latitude and Longitude attributes in
  this accession's 1 constituent entities identified in section
  5: Entity and Attribute Information
1.5.1.1 West Bounding Coordinate: changed from -180.000 to -180.000
1.5.1.2 East Bounding Coordinate: changed from 180.000 to 179.900
1.5.1.3 North Bounding Coordinate: changed from 90.000 to 90.000
1.5.1.4 South Bounding Coordinate: changed from -90.000 to -90.000
6.2 Resource Description: set to "NODC ACCESSION # 0058704"
6.4.2.1.7 Transfer Size: changed from 15000000 to 2.632 (actual)
6.4.2.1.7 Transfer Size: changed from 15000000 to 2.632 (actual)
6.4.2.1.7 Transfer Size: changed from 15000000 to 2.632 (actual)
7.1 Metadata Date: changed from 20041023 to 20091014
7.2 Metadata Review Date: changed from 20041023 to 20091014
7.3 Metadata Future Review Date: changed from 20050331 to 20101014
