OBSERVATION RESEARCH FOR THE MEASURING RAINFALL CAPACITY OF TRMM/TMI-85.5G BASED ON PRECIPITATION DATA DURING THE HEAVY RAIN EXPERIMENT IN SOUTHERN CHINA

摘要

The capacity of Tropical Rainfall Measuring Mission (TRMM) Satellite for measuring rainfall was examined by using TMI-85.5 GHz microwave image data and precipitation data during a heavy rainfall experiment in southern China. From comparisons with the distribution of rain amount in an hour with BBT of 85.5 GHz microwave, it is clear that the center of heavy rain corresponds with an area of low BBT value. The location and shape of BBT distribution is similar to that of precipitation, and the larger the rainfall rates, the lower the BBT. A statistic analysis shows that the correlation coefficients between BBT and rain rates is negative and significant. Especially, when the rain rate is over 7 mm/h, the correlation degree between BBT and rain rates is more significant. The results shows that TRMM/TMI-85.5 G has great ability to measure con-vective heavy rain.1 INTRODUCTION The Tropical Rainfall Measuring Mission (TRMM) satellite was jointly launched by the United States and Japan in November 1997. Aiming at acquiring more understanding of the effect of tropical precipitation on global climate systems, it was a mission in space aircraft for initial qualification of tropical rainfall measurements[1]. Detectors onboard the satellite included a micro-wave imager, precipitation radar, visible and infrared radiometer, lightening detector and earth radiation detector. With a swath of 760 km, the microwave imager with 5 frequencies was to measure the intensity of precipitation over the ocean over 5 frequencies. The frequency of 85.5 GHz with horizontal resolution of 4.4 km, was specially designed for detecting convective precipi-tation on the mesoscale and fine scale. The physical mechanism[2] with which convective precipitation is sensed with microwave at 85.5 GHz is based on the fact that ice crystals in the upper portions of convective systems scatter the 85.5-GHz-microwave intensely, which leads to considerable reduction of the upward