Rain Estimation in Extratropical Cyclones Using GMS Imagery

Abstract

A technique is presented which provides estimates of rainfall from extratropical cyclones over an area of 125 000 km2 in southeastern Australia in simulated real time conditions. It utilizes a statistical relation between blackbody temperature of cumuliform cloud and 90 minute rainfall totals to determine estimates of rainfall from cumuliform cloud, and approximates the lesser rainfall amounts from the stratiform pre?frontal cloud as a fixed proportion of rain from equivalent cumuliform cloud. It is based on the digitized ?HR Fax? imagery received at 3 h intervals from the Japanese Geostationary Meteorolgical Satellite (GMS). Five case studies are presented, each for a 24 hour period. Rainfall estimates for rainfall districts within the area vary from the observed district averages, which were calculated from daily gage data, by an average of 22%. The mean absolute error for districts is 4.2 mm.