Extreme precipitation Indices Derived from the NOAA CPC Unified Precipitation Data: Implications for Decision-Making

Key element of the water resource management practices is the need to manage risks associated with extreme precipitation events. A precise understanding of the frequency and intensity of these events and their influence on the local economy and agriculture is critical for implementing robust management practices and policy decisions with respect to water resources. This study focuses on deriving extreme precipitation indices and long-term climatological statistics from the NOAA Climate Prediction Center (CPC)'s Unified Precipitation Data for the 1950-2006 time period and translation to risks and actionable information that can be readily used by planners and policy makers. The NOAA CPC data set is validated against the Parameter-elevation Regressions on Independent Slopes Model (PRISM) gridded precipitation dataset and the Automated Surface Observing System (ASOS) station data. A variety of extreme precipitation indices such as maximum length of wet and dry spells, number of wet, heavy and very heavy precipitation days are derived from the daily precipitation dataset on seasonal, yearly and decadal scales to assess the regional trends in the extreme precipitation metrics. In addition, the extreme precipitation event climatologies are translated to sustainability and risk indices to flag vulnerable regions. Our results indicate that the CPC's unified precipitation dataset provides the necessary detailed output that is critical for deriving reliable decision aids with respect to extreme precipitation events.