Twice on August 12, 2016 GPM flew over a massive rainstorm that flooded large portions of Louisiana. The flooding was some of the worst ever in the state, resulting in a state of emergency. Tens of thousands of people were evacuated from their homes in the wake of this unprecedented event.
Throughout the course of August 12 (UTC) GPM captured the internal structure of the storm twice and GPM IMERG measured the rainfall accumulation on the ground.
NASA's GPM satellite is designed to measure rainfall using both passive microwave (GMI) and radar (DPR) instruments. DPR can observe 3D structures of radar signals reflected by rain and snow in a narrower swath.
IMERG is a NASA data product that combines data from 12 different satellites into a single seamless map. IMERG covers more of the globe than any previous precipitation data set and is updated every half hour.
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 22.214.171.124.0