Beginning in 2004, the International Precipitation Working Group (IPWG) began a satellite precipitation algorithm validation/intercomparison project over three domains (continental United States, Australia, and northern Europe) covered by quality-controlled surface networks. Its aim is to provide information to users on the daily-scale performance metrics (bias, RMSE, skill score, etc) relative to ground networks, and give algorithm developers a better understanding of the strengths and weaknesses of different algorithmic approaches and satellite data blends. A secondary aim is to investigate when and where satellite rainfall estimates generally perform better or worse than short-term rainfall predictions from NWP models. These validation activities were motivated by expanding requirements in climate modeling, data assimilation, nowcasting, and hydrological applications.

The development of high resolution precipitation products (HRPP; typically blends of low Earth orbiting passive microwave radiometric (PMW) and geostationary-based imagers) has also proceeded to the point where a more thorough analysis of their performance is required. The goal of the expanded Program to Evaluate High Resolution Precipitation Products (PEHRPP) is to characterize as clearly as possible the errors in various HRPP on many spatial and temporal scales, over variable background surfaces, and across seasons and climate regimes. Furthermore, errors of and differences between HRPP are meaningful in that they can be systematically related to precipitation characteristics and/or algorithm methodology, thereby potentially improving HRPPs by combining products or methods based on the observed errors and differences. In this presentation we will provide an overview of the validation strategies and summarize validation results to date, including results from the recently concluded PEHRPP workshop held in Geneva, Switzerland.