ON THE TROPICAL RAINFALL MEASURING MISSION (TRMM)

The importance of quantitative knowledge of tropical rainfall, its ass ociated latent heating and variability is summarized in the context of climate change. Since the tropics are mainly covered with oceans, wit h some deserts and jungles, the monthly precipitation is not known wit hin a factor of two. Hence the only way to measure it adequately for c limate and general circulation models is from space. The paper describ es the Tropical Rainfall Measuring Mission (TRMM). This joint Japan-U. S. cooperative Earth Probe satellite will be launched from Japan in 19 97 for a three-year mission. The scientific basis of the instrument an d orbit selection is explained. The precipitation instrument complemen t comprises the first rain radar to be flown in space (PR), and a mult i-channel passive microwave sensor (TMI) improved relative to the SSM/ I-1 by an additional channel at 10 GHz. The third rain instrument is a live-channel VIS/IR (VIRS) sensor. Progress in construction of instru ments, observatory, data system, and the ground validation program is summarized. A report is also given concerning development of the algor ithms by which rainfall and its associated latent heat release will be calculated from the several instruments, separately and in combinatio n, and how the scientists will interact with the data system to obtain the 32 rain data products necessary to fulfill the science requiremen ts.