Estimating Extreme Rainfall from Polarimetric Radar

Abstract:

Accurate measurement of extreme rainfall rates at high spatial and temporal resolution is crucial to the study of extreme flooding. Analysis of probable maximum precipitation (PMP), which is frequently used for the design of high-hazard structures, relies on accurate rain rate fields. The polarimetric upgrade to the US network of WSR-88D radars provides potential for significant improvement of extreme rain rate estimates. Through radar rain gauge intercomparison using a catalog of storm events, we test a rainfall algorithm that focuses on the use of specific differential phase (KDP). We analyze performance at a variety of temporal scales, focusing on time scales from 5 minutes to 3 hours. Spatial resolution of rainfall fields ranges from 0.5 to 1.0 km. This algorithm shows improved accuracy relative to other algorithms for estimating extreme rainfall rates. We present results from a wide range of geographic settings and climates across North America (focusing on urban areas), including Baltimore, Houston, Phoenix, Kansas City, and St. Louis. Our analyses also span a broad spectrum of convective precipitation, demonstrating the widespread applicability of the KDP algorithm.