Hydrologic Assessment of Remotely Sensed High Resolution Precipitation Products over Cold-Mountainous Regions, and Analysis of the GPM Impact

Remote sensing of precipitation in mountainous and snow-fed basins is challenging, but critical for hydrometeorological applications and water resources management. This study is part of the ongoing effort to develop a Regional Hydrological Extremes Assessment System (RHEAS). Five commonly used satellite-based high-resolution precipitation products (HRPPs) over several basins in the mountainous western United States are investigated. The products (TRMM 3B42, TRMM 3B42-RT, CMORPH, PERSIANN, and PERSIANN-CCS) are analyzed using ground gauge and gauge-adjusted radar precipitation data. In order to diagnose the sources of errors, level 2 products are also explored (AMSR, AMSU, TRMM TMI, TRMM PR, and CloudSat). CloudSat provided useful insight on light rain and snowfall and was used as an additional resource to improve the analysis. For hydrologic assessment, the skill of HRPPs and the resulting streamflow simulations from the Variable Infiltration Capacity (VIC) hydrological model is cross-compared. It was found that over the mountainous west US basins, HRPPs often capture major precipitation events, but seldom capture the observed magnitude of precipitation, especially during winter when snowfall is dominant. Bias adjustment is found to be effective in enhancing the HRPPs and resulting streamflow simulations. The results using collocated AMSR-E, CloudSat, and AMSU suggest that current limitations in retrieving snowfall, precipitation from systems that lack frozen hydrometeors, and systems over frozen land contribute largely to the observed errors transferred to HRPPs. In light of the operation of the GPM mission, further opportunities for enhancing snowfall retrieval and hydrology of cold and mountainous regions are becoming available. We provide some initial assessment of the latest GPM observations and discuss about the impact of GPM over cold-mountainous basins.