Geostationary IR Channel Brightness Temperature - GridSat B1

Status

  • Version: v02r01
  • Last updated: April 2014
  • Period of record: January 1980 - March 2014
  • Update frequency: Quarterly
  • Version change log (changes from v01r01 to v02r01):
    • Expansion of record to present
    • New variables:
      • irwin_vza_adj - Used to revert back to the infrared window brightness temperature prior to the view zenith angle correction
      • Raw visible data - Raw visible channel DN from the B1 data are optionally available from the PI. This can help given some issues with visible channel calibration.
    • More complete metadata (numerous new global and variable attributes in netCDF files).
    • Processing now creates netCDF 4 files directly (v01r01 used ncks to do the conversion).
    • Bug fixes:
      • More thorough QC of bad images. Now ignores an image with too few scan lines and very noisy images.
      • Navigation uses corrected image center.
      • Corrected variable output. Problem was that some variables weren't output when a channel from one satellite was missing. This impacted vschn and irwvp more often. The correction now ensures all available data are output. Correction resulted in improved coverage of irwvp and vschn, but did have a small impact on improving the irwin coverage.
      • Calibration corrected if one satellite is much warmer or colder than its neighbors
  • Known Issues:
    • CDR parameter: irwin_cdr - The Infrared window channel is the only parameter having CDR quality
    • Infrared water vapor (irwvp) data is provided with some post calibration but data gaps and some calibration issues remain. Users should inspect irwvp channel quality prior to use.
    • Visible data (vschn) data are of low quality and are present solely for visualization purposes. A future version of GridSat-B1 data will have inter-calibrated vschn data
    • Early data may have navigation issues due to unreliable navigation information. For example, misnavigation can cause misplacement of the satellite data such that coastlines do not align with map overlays.
    • Meteosat satellite position parameters (satrad, satlat, satlon) represent the reprojected, opitmal position. This is often accurate, but for late in the life of Meteosat-5 and Meteosat-7 (both over the Indian Ocean), the sub-satellite point varied widely from the Equator. Calculation of viewing geometry during these periods will not be accurate.
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