Changes in the Precipitation Processing Subsystem (PPS) of the WSR-88D (NEXRAD) in 2004–2009

In early 2004, changes were made (in software Build 5) to the Precipitation Detection Function (PDF) and Precipitation Preprocessing algorithm that ultimately result in radar rainfall estimation products from the WSR-88D (NEXRAD) weather radar. The new algorithm that combined the PDF with Precipitation Preprocessing is called Enhanced Precipitation Preprocessing (EPRE). The parameters for EPRE are in the process of being adjusted based on topography, climate, and current or imminent weather conditions (vertical temperature and humidity profiles and anticipated precipitation type). This paper summarizes (1.) the algorithm changes and (2.) the observed impact of these changes on radar rainfall estimates.