Quantitative Inter-Comparison Between GPM Dual-Frequency Precipitation Radar Observations and Polarimetric Ground Radar Measurements

Abstract

The dual-frequency precipitation radar, also known as DPR, on board the Global Precipitation Measurement (GPM) mission Core Observatory is capable of taking measurements simultaneously at both the frequency channel of 13.6 GHz (Ku-band) and 35.5 GHz (Ka-band). Since the DPR is limited to operate only on single polarization, most of the retrievals are based on back scattered power measured by the radar. Accurate retrieval of rainfall rate and various microphysical properties requires minimizing the uncertainties in reflectivity measurements. In this study, GPM-DPRs simultaneous observations are evaluated quantitatively against measurements from well calibrated dual polarization ground radars. It is bit of a challenge to compare the space and ground radar's observations. Owing to their difference in viewing geometry, alignment and resolution volume it is difficult to perform a quantitative comparison on a point by point basis. To this end, a volume matching technique is applied to align and resample the data to a common grid. Comparison studies of measurements such as radar reflectivity and radar rainfall rate are performed. As a result of this comparison, the GPM-DPR's attenuation correction algorithm is also assessed. Finally the errors in DPR measurements are quantified and presented in terms of statistical scores.