Global Satellite Composites – 20 Years of Evolution

For the past 20 years, the University of Wisconsin Space Science and Engineering Center (SSEC) and the Antarctic Meteorological Research Center (AMRC) have been creating global satellite composites. These composites have proven to be useful for research, operational forecasting, aviation and educational outreach. Over the years, each of these groups came to the realization that the original composites did not meet their needs and unique composites and algorithms began to evolve. AMRC was the first group to begin using satellite composites. Using the Man computer Interactive Data System (McIDAS) software developed at SSEC infrared window (IR) composites were created by combining geostationary and polar orbiting data from the SSEC's Data Center and flyover polar data acquired from McMurdo Station, Antarctica. Animations of these images gave forecasters their first look at fast moving polar storms which gave way to improved forecasts. Similar composites are now being used to calculate wind vectors based on cloud drift. The hope is to infuse this wind data into numerical models thereby creating better initializations. The first algorithm, which is still used today, uses the minimum brightness temperature of all co-located pixels that fall within a specified time range. Newer algorithms have been developed that look at parallax errors, distances from the sub-satellite point and the time for each co-located pixel to correct for the deficiencies of the original technique. Utilizing improved computer capabilities, we are now making hourly composites of visible, IR, short-wave IR, long-wave IR and water vapor channels. A review of this evolving application of satellite observations is outlined including an initial evaluation of algorithms.