Recent improvements to the TRMM Microwave Imager Land Rainfall algorithm

This paper describes recent improvements to the Tropical Rainfall Measurement Mission (TRMM) Microwave Imager (TMI) land rainfall algorithm. The relationships between rain rates and TMI 85 GHz brightness temperatures (Tb) for convective and stratiform rain were estimated using 7 years of collocated TMI and TRMM Precipitation Radar (PR) data. The TMI algorithm for estimating the convective ratio of rainfall has also been modified, and further changes are under consideration. We will discuss both the changes made to the TMI land rainfall algorithm and the continuing problems with the land rainfall retrievals. We will demonstrate that the recent changes to the algorithm significantly lower the over-estimation by TMI globally and over large sections of Central Africa and South America. We will also highlight the problems with the TMI land algorithm that are currently being addressed, such as large regional and seasonal dependence of biases in the TMI rain estimates, and discuss potential changes to the algorithm to reduce these problems.