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Presentation of the Products

Atlantic Surface Solar Irradiance

Physical definition

The SSI is the solar irradiance reaching the Earth surface in the 0.3-4 µm band, the irradiance being the radiant flux received per unit area. This defines an instantaneous SSI value, which corresponds to the definition of the hourly SSI. The 3-hourly and daily SSI values are mean values over the considered period of time, 3 or 24 hours.

Delivered products

The delivered SSI products are :

• The LML SSI, 3-hourly products on LML area, derived from the geostationary satellites data (GOES and MSG), covering the oceanic area from 60 N to 60 S and from 100 W to 45 E, at 0.1 degree resolution,
• The MAP SSI, daily products on MAP area, derived from GOES, MSG and NOAA polar orbiter satellite data, covering the oceanic area from 90 N to 60 S and from 100 W to 45 E , at 0.1 degree resolution.

Fluxes products are accessible to all users on Météo-France and IFREMER ftp servers, via EUMETCAST, and may be delivered on request through the Regional Meteorological Data Communication Network (RMDCN) to the European Meteorological services.

Units

SSI values are expressed in tenths of in W/m2 and coded in 16-bit words. Unprocessed data, for whatever reason, are equal to -32768 in HDF format or flagged as missing in GRIB section 3.

Quality indexes

Each SSI field is associated with a quality index, which includes a confidence level corresponding to the quality of the calculated SSI and information on the processing conditions.

Satellites data sources

The LML Fluxes products are derived from Met-08 and GOES-12.
The MAP Fluxes are derived from Met-08, GOES-12 and NOAA polar satellites.

Processing scheme

• At Met.no :

  At each satellite pass (NOAA and further METOP) received at Met.no, data are processed to produce HL SSI fields.
  
  

• At CMS :

  GOES or MSG images are processed every hour at M-F/CMS, Lannion, producing instantaneous solar irradiance fields. These instantaneous fields are called hourly SSI, because of their time sampling.
  The hourly SSI fields are combined to produce 3-hourly and daily SSI fields. All these tasks are performed separately for each satellite, GOES or MSG.
  The GOES and MSG 3-hourly or daily SSI fields are merged into a LML product.
  Finally, the daily LML and the daily HL, derived from NOAA and produced by Met.no and DMI , are merged into the MAP product.
  In overlapping areas, two satellite values are available and the merging process is a choice between them.
  The method is based on a physical parameterization of the SSI as a function of the Top of Atmosphere (TOA) albedo, which is derived from the satellite visible image (one channel for GOES, two channels for NOAA or MSG). The SSI calculation scheme also uses auxiliary parameters, as shown below for GOES.

LML SSI calculation scheme

Current parameters:

• GOES-E configuration file.
• Meteosat configuration file.