Thursday, 30 October 2008: 2:15 PM
South Ballroom (Hilton DeSoto)
The Tropical Rainfall Measuring Mission (TRMM) satellite has been used to infer distributions of intense thunderstorms. Passive microwave brightness temperatures are used as proxies for convective vigor. This is based on large graupel or hail lofted by strong updrafts being the cause of extremely low brightness temperatures in the 85 and 37 GHz channels. This study seeks to empirically confirm that extremely low brightness temperatures are often accompanied by large hail at the surface, and map hailstorm locations based on that. The three frequencies examined (85, 37, and 19 GHz) all show an increasing likelihood of hail reports with decreasing brightness temperature. Hail reports become somewhat common with 37 (85) GHz brightness temperatures below 200 (80) K.
Hail reports in the United States are used to quantify hail versus birghtness temperature relationships. There is considerable quantitative uncertainty, using instantaneous "snapshots" of brightness temperature from low-earth orbiting satellite together with spotter reports that may not establish the complete times and locations of hailstorms. After using the United States database for "training" the satellite measurements, global distributions of likely hailstorms are mapped using TRMM and AMSR-E passive microwave brightness temperatures.
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