The TRMM Microwave Imager (TMI) is a 5-channel, dual-polarized, passive microwave radiometer. Microwave radiation is emitted by the Earth's surface and by water droplets within clouds. The TMI is used to measure several important meteorological parameters over sea surfaces. The TRMM orbit was selected for continuous monitoring of the tropics. To achieve this, a low inclination angle was chosen, ... confining the TRMM observations between 40°S and 40°N. Previous microwave radiometers were either too poorly calibrated or operated at too high of a frequency to provide a reliable estimate of SST. The TMI, a successor to the SSM/I, measures radiation at frequencies of 10.7, 19.4, 21.3, 37, 85.5 GHz. It orbits at an altitude of 218 miles, much lower than the SSM/I, thus providing better resolution. From the 5 channels of data provided by TMI, scientists calculate several parameters over ocean surfaces. This data is archived at the Global Hydrology Resource Center (GHRC) in Huntsville, Alabama.
[Summary provided by the University of Alabama, Huntsville.]