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Clear Sky Brightness Temperature Derived from the GOES Imagers
Since November 2001, CIMSS has been determining Clear Sky Brightness Temperature
(CSBT) information from the GOES Eastern and Western Imagers. These observed
data are provided to the National Center for Environmental Prediction (NCEP)
in Washington D.C. and the European Centre for Medium-range Weather Forecasts
(ECMWF) in England for assimilation into global weather prediction models. Processing
is hourly and hemispheric with respect to temporal and spatial coverage, respectively.
Coverage for the CSBT extends from roughly 67S to 67N and 30W to 165E. The resolution
is averaged over boxes of approximately 50 km. Each box consists of 187 (11 rows
by 17 columns) fields-of-view (fovs). For a given box, a cloud detection algorithm
(Schreiner et al, 2001) is used. This clear/cloudy determination is based on
brightness temperature comparisons with neighbors as well as surface information
provided by hourly observations where available and numerical forecasts and remotely
sensed sea surface temperatures over the oceans. For each 50 km box, the average
brightness temperature for each infrared (IR) band and the albedo for the visible
band are calculated along with the average clear and cloudy brightness temperatures.
Additional parameters are the number of clear and cloudy fovs, center latitude
and longitude of the box, central local zenith and solar zenith angles of the
box, land/sea flag, standard deviation of the average clear and cloudy brightness
temperatures, and two quality indicator flags. The processing is performed using
the McIDAS system and the output information is then transferred from a McIDAS
Meteorological Data (MD) file into a Binary Universal FoRm (BUFR) file. Full
hemispheric images are produced every 3 hours for the 24 hour loops below. Notes:
The displayed CSBT product above is of the GOES Imager water vapor channel brightness
temperature. The infrared and visible overlay images have been enhanced.
Menzel, W.P., Schmit, T.J., and Schreiner, A.J., 2001: Observations and Trends of Clouds Based on GOES Sounder Data, Journal of Geophysical Research - Atmospheres, 106 , 20,349-20,363
Article from 2003 AMS Conf.