The TMI instrument on the TRMM satellite measures microwaves emitted from the Earth's land and water. By comparing emission from different microwave frequencies, the characteristics of ice and water in the atmosphere can be determined. For example, 85 GHz microwaves are scattered by ice crystals in tropical cyclones, making cyclone rain bands appear 'colder' than the surrounding areas. By comparing 85 GHz temperatures in different polarizations with other frequency band measurements, accurate measurements of rainfall in the atmosphere can be made. This animation shows eight days of global TMI 85 GHz measurements in the Gulf of Mexico during Hurricane Katrina. The hurricane Katrina rainbands clearly show up in these images.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 18.104.22.168.0