| Summary: | A Group for High Resolution Sea Surface Temperature (GHRSST) dataset for the North Atlantic Region (NAR) from the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-17 platform (launched on 24 Jun 2002). This particular dataset is produced by the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) Ocean and Sea Ice Satellite Application Facility (OSI SAF) in France. The AVHRR is a space-borne scanning sensor on the National Oceanic and Atmospheric Administration (NOAA) family of Polar Orbiting Environmental Satellites (POES) having a operational legacy that traces back to the Television Infrared Observation Satellite-N (TIROS-N) launched in 1978. AVHRR instruments measure the radiance of the Earth in 5 (or 6) relatively wide spectral bands. The first two are centered around the red (0.6 micrometer) and near-infrared (0.9 micrometer) regions, the third one is located around 3.5 micrometer, and the last two sample the emitted thermal radiation, around 11 and 12 micrometers, respectively. The legacy 5 band instrument is known as AVHRR/2 while the more recent version, the AVHRR/3 (first carried on the NOAA-15 platform), acquires data in a 6th channel located at 1.6 micrometer. Typically the 11 and 12 micron channels are used to derive sea surface temperature (SST) sometimes in combination with the 3.5 micron channel. The highest ground resolution that can be obtained from the current AVHRR instruments is 1.1 km at nadir. The NOAA platforms are sun synchronous generally viewing the same earth location twice a day (latitude dependent) due to the relatively large AVHRR swath of approximately 2400 km. The NAR products are SST fields derived from direct broadcast High Resolution Picture Transmission (HRPT) AVHRR data that are re-mapped onto a stereopolar grid to produce mosaics at 2 km resolution. An operational AVHRR cloud mask is applied based on a multi-spectral thresholding algorithm (Derrien and Le Gleau 1999). Some refinements specific to the marine conditions have been introduced including the use of fine scale climatology and a fine gradiant climatology to assist in the detection of clouds in areas characterised by strong thermal gradients. L2P data products are then derived following the GHRSST-PP Data Processing Specification (GDS) version 1.5 including Single Sensor Error Statistics (SSES). Although the dataset designation is "L2P" it is actually a "L3C" dataset (gridded Level 3 collated) as defined by the GHRSST Data Processing Specification version 2.0. This dataset was originally produced for the GHRSST Pilot Project (GHRSST-PP), the precursor to GHRSST, by the Medspiration Regional Data Assembly Center (RDAC) in Europe. As one of the first datasets produced as a prototype for the GHRSST-PP it assumed an incorrect designation of "L2P".
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