Radar and Disdrometer Observations of Topographical Effects on the Melting Layer and Resultant RSD

Commonly used techniques to measure precipitation are often challenging in mountainous regions where topographical enhancement can cause highly variable precipitation patterns. Although space-based radars, such as the Dual-frequency Precipitation Radar onboard the Global Precipitation Measurement (GPM) mission core satellite, provide an ideal vantage point for mapping precipitation in such regions, the complexity of the terrain often prohibits retrieval of precipitation near the surface. Hence to help determine the variability of precipitation within this lower part of the atmospheric column we investigate vertical profiles of precipitation obtained from dual-polarimetric radar RHI scans and disdrometers deployed during GPM Ground Validation (GV) field campaigns on the Olympic Peninsula and the southern Appalachian Mountains. From these measurements we compare characteristics of the raindrop size distribution (RSD) and the melting layer at different topographical elevations and for these two very different climate types. Indeed, topography influences the size and concentration of raindrops, but the melting layer can provide an additional constraint for retrieving the RSD in complex terrain where the DPR has difficulty resolving the rain signal.