Reflectivity Uncertainties and their Impact on Raindrop Size Distribution Parameters Retrieved from Vertically Pointing Doppler Profiling Radars

Vertically pointing profiling radars (profilers) observe the vertical structure of precipitating cloud systems as they pass directly overhead. Profilers are part of the instrument suite used in NASA Precipitation Measurement Mission (PMM) Ground Validation (GV) field campaigns to identify and diagnose the reflectivity vertical structure during convective and stratiform rain regimes. The raindrop size distribution (RDSD) throughout the rain column can be estimated from collocated profilers operating at 50- and 920-MHz as was the case near Darwin, Australia, during the Tropical Warm Pool International Cloud Experiment (TWPICE). But the accuracy of RDSD rainfall parameters (e.g., median raindrop diameter and rainfall rate) is dependent on the reflectivity uncertainty. This study investigates the reflectivity uncertainty of vertically pointing profiling radars by examining the power fluctuations of the observed Doppler velocity power spectra. These power fluctuations directly contribute to the reflectivity uncertainty and provide measurement error inputs for optimal estimation retrieval methods that generate RDSD rainfall parameters with uncertainties. Using observations collected during TWPICE, it was determined that reflectivity uncertainties decrease with increasing dwell period. The rainfall reflectivity uncertainty decreased from about 0.25 to 0.1 dBZ as the dwell period increased from 9- to 60-seconds. A poster will be presented at the conference that shows that the decrease in retrieved RDSD rainfall parameter uncertainties is dependent on the reflectivity uncertainty as well as the shape of the raindrop size distribution.