Validation of rainfall estimates from the TRMM precipitation radar and microwave imager using a radiative transfer model: 1. Comparison of the version-5 and -6 products

[1] The Tropical Rainfall Measuring Mission (TRMM) version-6 rainfall products show the reduced bias between Precipitation Radar ( PR) and TRMM Microwave Imager (TMI) rainfall estimates during the 1997/1998 El Nino event noted in version 5, but need to be verified. We investigate consistency between TMI-observed brightness temperatures (TBs) at 10 and 19 GHz channels and those simulated from the PR and TMI rainfall estimates using a radiative transfer model. Simulated TBs from PR V6 exhibits better agreement with observed ones than those from PR V5, implying the algorithm improvements. However, discrepancies at 19 GHz suggest that uncertainty in the assumed drop size distribution still remains in PR V6. Simulated TBs from TMI V6 also exhibits better agreement with observed ones than those from TMI V5. However, the simulated 10-GHz TBs from TMI V6 exhibits more scatter against TMI-observed ones than those from PR V6 do.