Using New Versions of the GPCP and TMPA Data Sets to Assess Interannual Variation of Tropical Precipitation

Two highly popular precipitation data sets, the Global Precipitation Climatology Project (GPCP) and TRMM Multi-satellite Precipitation Analysis (TMPA), underwent significant upgrades and were made publicly available during the past year. In both cases, improvements in the constituent data sets and advances in their underlying precipitation algorithms were incorporated. Analysis of these and related data sets will allow us to better assess our knowledge of the interannual variation of tropical precipitation.

The new Version 2.2 GPCP features upgrades to the Microwave Emission Brightness Temperature Histograms (METH) emission algorithm over ocean, and to the NOAA scattering algorithm and GPCC gauge analysis over land. The new Version 7 TMPA uses more consistent sources of satellite input data and gauge analyses than in the previous version. Both GPCP and TMPA now use F17 SSMIS data to extend their respective data records to the near-present. Time series of oceanic precipitation, focusing on similarities and differences between GPCP and TMPA, will be presented.

In addition, results from experimental versions of the two data sets will be shown. Within GPCP, the METH algorithm is replaced with GPROF2010, a more modern microwave retrieval algorithm. Results for the pre-SSMIS era will be compared against the official Version 2.2 record. For TMPA, the new retrospectively-processed real-time version will be examined against the official Version 7 data. A comparison of all four methods for a common period should bolster confidence in our state of knowledge of interannual variability when they track well together, while potentially yielding insights into the strengths and weaknesses of the individual methods where they differ. Such observational data should prove beneficial to climate model initialization and verification.