Vertical profiles of reflectivity over complex terrain and their impact on WSR-88D radar QPEs: case studies from the NOAA Hydrometeorological Testbed

Non-uniform vertical profile of reflectivity (VPR) is one of the major error sources in radar-based quantitative precipitation estimation (QPE). Without observations of a “true” VPR, it is difficult to quantify radar QPE uncertainties associated with non-uniform VPRs. Data collected by high-resolution precipitation profiling radars deployed along the west slope of the Sierra Nevada during the NOAA Hydrometeorological Testbed (HMT; http://hmt.noaa.gov) experiment in northern California provide a great opportunity for such studies. The two intensive operation periods to be discussed occurred over the periods 30 December 2005 to 1 January 2006, and 13 to 15 January 2006. Reflectivity observations from several WSR-88Ds (Weather Surveillance Radar -1988 Doppler) were compared with very high-resolution VPRs observed by the HMT S-band precipitation profilers. Precipitation estimates were generated from the WSR-88Ds using a variety of techniques, and the impact of non-uniform VPRs on radar precipitation estimates was analyzed. Large vertical variations of reflectivity were found in the profiling-radar VPRs. The WSR-88D radar beams are too wide to resolve such variations, especially at far ranges. Various VPR correction approaches were tested and detailed results will be presented at the conference.