Intercomparison of the Version-6 and Version-7 TMPA precipitation products over high and low latitudes basins with independent gauge networks: Is the newer version better in both real-time and post-real-time analysis for water resources and hydrologic ext

The TRMM Multi-satellite Precipitation Analysis (TMPA) system underwent an important upgrade in early 2013, at which the newest Version-7 TMPA products were formally released. In this study, the TMPA successive versions, original Version-6 and current Version-7, were evaluated and intercompared by using independent gauge observation networks for a 7-yr (2003–09) period over two representative basins in China at different latitude bands. The TMPA products studied are the Version-6 and Version-7 real-time 3B42RT estimates (RTV6 and RTV7) and post-real-time 3B42 estimates (V6 and V7). Assessments indicate that RTV7 represents a substantial improvement over RTV6 with respect to the systematic bias in the low-latitude Mishui basin, reaching similar accuracy levels as with the gauge-adjusted research products. But, such improvement was not found in the high-latitude Laohahe basin, suggesting that the current Version 7 TMPA real-time estimates still have much room for improvement at high latitudes. On the other hand, the post-real-time research product V7, which is expected to provide better precipitation information for water resources management in ungauged regions, generally outperforms V6 over both gauged basins and has the best performance among the four standard TMPA estimates. The seasonal analyses show that the new Version-7 algorithm notably reduces the bias between TMPA and observations during winter months for the low-latitude Mishui basin, but fails to effectively alleviate the serious overestimation for winter precipitation occurring in the high-latitude Laohahe basin. The study also reveals that all the TMPA products significantly underestimate high rain rates over the Mishui basin, especially for strong typhoon events during summer. Thus, caution should be exercised when applying the current Version-7 TMPA products for simulation and prediction of hydrologic extremes associated with heavy rainfall, such as floods or landslides.