9:30 AM - 9:45 AM
[ACG46-21] DSD database for the GPM/DPR precipitation retrieval algorithm
Keywords:GPM, DPR, drop size distribution
In the precipitation retrieval algorithm of the Dual-frequency Precipitation Radar (DPR) of the Global Precipitation Measurement (GPM) mission core satellite, the relation between the mass-weighted mean drop size (Dm) and R (R-Dm relation) is used. As both R and Dm are independent of radar frequency, R-Dm relation is useful in the dual-frequency algorithm and it may be extended for other radar measurements.
The standard R-Dm relation in the DPR algorithm was derived from Z-R relation which Kozu et al. (2009) proposed based on precipitation measurements in Tropics. It may not be appropriate and need to be modified for mid- and high-latitude precipitation within the DPR coverage.
In the DPR algorithm, at each pixel, R-Dm relation is modified by the Surface Reference Technique (SRT), while the SRT does not work well for light precipitation. However, dual-frequency measurements make it possible to adjust R-Dm relation for light precipitation.
The figure shows estimates of R and Dm for over-land convective precipitation cases by single-frequency (SF) algorithm (Fig. a) and dual-frequency (DF) algorithm (Fig. b) in the version-4 DPR algorithm. For weak precipitation, SF algorithm mostly follows the standard R-Dm relation, but DF algorithm gives larger Dm estimates.
Based on DF estimates, optical R-Dm relations are calculated for seasons and regions. They are summarized as DSD database. The new R-Dm relations are used for SF algorithm in the version-5 DPR algorithm (Fig. c). As a result, SF and DF algorithms give closer Dm for weak precipitation. As the next step, the DSD database needs to be validated and improved with ground-based measurements.