OSI-SAF LEO SST

Summary

Provider: SAF on Ocean and Sea Ice - Météo-France - Centre de Météorologie Spat- Avenue de Lorraine - BP 50747 - 22307 LANNION CEDEX - FRANCE

Contact person: OSI-SAF Manager (Send mail)

Contact for production: CMS (Send mail)

Algorithm development: Météo-France/CMS(Send mail)

Atlantic Sea Surface Temperature Product Manual : http://www.osi-saf.org/biblio/docs/ss1_pmatlsst_1_6.pdf

Low Earth Orbiter (LEO) Sea Surface Temperature (SST). Sea surface temperatures can show features like fronts, eddies, coastal upwelling, currents etc. delineating different water masses. SST is used by environmental, marine, meteorological and climate organizations for seasonal forecasts, climate change detection, environmental approach, and productivity.

Values range between ~270K and ~308K (the unit is CentiKelvin)

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Platform & processing

AVHRR data from MetOp and NOAA satellites are processed every hour, twice daily.

. Hourly SST fields are combined to produce 3-hourly products then merged.

Satellite GOES-E. Channels: 3.9μm, 10.7μm. (4 km resolution at nadir)

Satellite MSG. Channels: 3.9μm, 10.8μm, 12μm. (3 km resolution at nadir)

Subskin SST : Comparable to in situ (buoy) measurements at night.

Relation to bulk SST : equivalent to bulk SST by night. By day, a bias of several Kelvin may be found underfavorable diurnal heating conditions.

Relation to skin SST : by day and by night the subskin SST is convertible to skin temperature by subtracting 0.

2K.

Algorithm

The CMS (Centre de Météorologie Spatiale) processing chain generates the product. The processing software is not publicly available, it's a EUMETSAT property. Three algorithms have been selected : one for daytime (MSG only from T10.8μm & T2μm) and two for nightime (one for MSG from T3.9μm, T10.8μm & T12μm, and one for GOES-E from T3.9μm & T10.7μm).

The coefficients of the are given in tables.

Brightness temperatures data from GOES-E and MSG.

GOES: T3.9μm & T10.7μm at 4 km resolution at nadir.

MSG: T3.9μm, T10.8μm & T12μm at 3 km resolution at nadir

Main change when GOES-12 replaced GOES-8. The 12μm channel has been replaced with a 13.3μm channeonboard GOES-12 and since this replacement, it's impossible to calculate daytime SST in the GOES-E area. GOES-E and MSG data acquisition → Making of a cloud mask→ Control of the cloud mask through thvariation of T11μm. 1st SST calculations. Control of the cloud mask by comparison with the minimumclimatological values. Smoothing of the atmospheric correction. 2nd SST calculations. Quality control (visual and statistical)

Product uncertainties

Cloud cover limits coverage of the sea surface. One pixel/one temperature. Beware of confidence values ! GOES-E data are used to retrieve SST in night time only Archive is consistent.

Product dissemination

OSI-SAF LEO SST is distributed via EUMETCast-Africa (GRIB format). The product is delivered in GRIB format through Météo-France FTP server, in HDF and NetCDF format through thIFREMER FTP server. OSI-SAF LML SST available within 2 hours after the last satellite data acquisition.

Product validation

Product is peer reviewed. The GOES-E and MSG Match-up data bases have been built at CMS on a routine basis according to the following rules:

In situ data (buoy measurements) are collected daily. The corresponding satellite data are collected in 5*5 pixel (IR resolution) box centered on the buoy location providing the cloud coverage of the box is below 60%. These data include the SST calculated in the preoperational scheme and the brightness temperatures or reflectances of the imager channels averaged over the cloud-free pixels of the validation box. The MetOp product is compared every day with the MSG product. The outputs are also compared with data from buoys.

Data characteristics

OSI-SAF LEO GLB SST: Global coverage at 0.05 degree resolution.

60°N to 60°S, 100°W to 45°E

OSI-SAF LEO NAR SST: 2km resolution

OSI-SAF LEO MGR (GRIB, HDF & NetCDF) in cylindrical equidistant projection

OSI-SAF LML SST : less than 1 hour

Array of quality indexes: (5) excellent, (4) good, (3) acceptable, (2) bad, (1) erroneous, (0) unprocessed.

Notes

When the processing changes, archive is also usually reprocessed.

Useful references:

Brisson, A., P. Le Borgne, A. Marsouin, 1998, Development of algorithms for SST retrieval at O&SI SAF Low and Mid Latitudes. CMS report to EUMETSAT, Météo-France/CMS 22307 Lannion CEDEX, FRANCE

Francois, C., A. Brisson, P. Le Borgne and A. Marsouin, 2002, Definition of a radio-sounding database for sea surface brightness temperatures simulations: application to sea surface temperature retrieval algorithm determination, Remote Sens. Environ., 81, 309-326.