Background

Since 2005, ECMWF has generated model-simulated satellite images out to five days from the 00 UTC and 12 UTC  cycles of the operational HRES forecast for all operational geostationary satellites (i.e., MET-7, MET-10, MTSAT-2, GOES-13 and GOES-15). The simulated images are archived in MARS as GRIB edition 1 files and have been presented on the ECMWF website as PostScript image files. The forecast-generated satellite images have been based on the resolution of the HRES global model with 3-hourly output from T+0 to T+48 and 6-hourly output to step=120.

Up to and including IFS cycle 41r1, the satellite images in both the window and water vapour (WV) channels were simulated over each of the 5 geostationary satellite’s disk. Brightness temperatures were calculated using the same radiative transfer algorithm (e.g., RTTOV-11) as in the operational data assimilation and using the relevant atmospheric model profiles (temperature, specific humidity, ozone mass mixing ratio, cloud cover, specific cloud liquid water content, specific cloud ice water content, specific rain water content, specific snow water content) and the relevant surface parameters (skin temperature, 10m u and v wind components, 2m temperature and 2m dewpoint temperature, volumetric soil water layer 1, convective available potential energy).

Errors in simulated satellite images can derive from errors in the NWP parameters, on which the simulation is based, the resolution of the model and RTTOV model performance.

Updates to the simulated satellite images at IFS cycle 41r2

The simulated satellite images at IFS cycle 41r2 have been enhanced in various aspects.

• Global satellite images capturing detailed cloud and/or humidity features
  The new simulated images product shows the high-resolution ECMWF forecasts as a weather satellite will see it (e.g. Meteosat-10). The new simulated satellite image product includes latitudes greater than 60° north and south, extending the geostationary-type imagery over high-latitude regions. This is an enhancement with respect to the previous satellite image product which was limited to the Meteosat-10 disk domain.

• Nadir view for every model grid point
  The new simulated satellite images assume a nadir view for every model grid point so the effect of looking slantwise through the atmosphere is neglected. Consequently the atmosphere appears less opaque than with the old simulated images and so lower lying clouds and other features are better presented.
  
  
• Produced in post-processing within the IFS, with no mapping on satellite grid
  This is a technical advantage of the new simulated satellite images being now produced in the post-processing within the IFS and being part of the research tests for operational release. This is an enhancement with respect to the previous product generated only in the early delivery cycles of the operational suite as they can be now used routinely in ECMWF Research Department experiments to validate model developments which affect the temperature and moisture fields.
  
  
• Availability of the simulated satellite images in MARS
  The new images product are archived in MARS in GRIB edition 2 and are available at every post-processing step, out to 240 hours: 3 hourly from T+0 to T+48,  6 hourly from T+54 to T+120 and  then 12 hourly from T+132 to T+240. This is an enhancement with respect to the previous  satellite image product available in GRIB edition 1, out to T+120.
  
  
• Availability of the simulated satellite images in ECMWF Catalogue and dissemination
  The timeliness of delivery is optimal for dissemination. The new simulated images will be added to the list of products that can be requested in dissemination.

Technical information

Availability of the simulated satellite images in MARS

RETRIEVE,
    STREAM     = OPER,
    CLASS      = OD,
    EXPVER     = 0001,
    DATE       = -1,
    TIME       = 12,
    TYPE       = SSD,
    IDENT      = 57,
    INSTRUMENT = 207,
    PARAM      = 260510,
    CHANNEL    = 9,
    STEP       = 0/3/6/9/12/15/18/21/24/27/30/33/36/39/42/45/48/54/60/66/72/78/84/90/96/102/108/114/120/132/144/156/168/180/192/204/216/228/240,
    TARGET     = "meteosat-10.channel9.grib2"

Availability of the simulated satellite images in dissemination