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Optimized raindrop size distribution retrieval and quantitative rainfall estimation from polarimetric radar

Huang, Hao, Zhao, Kun, Zhang, Guifu, Hu, Dongming, Yang, Zhengwei
Journal of hydrology 2020 v.580 pp. 124248
hydrology, polarimetry, radar, rain, rain gauges, China
A variational approach for optimized drop size distribution (DSD) retrieval, attenuation correction, and rainfall estimation from polarimetric radar measurements (horizontal reflectivity factor ZH, differential reflectivity ZDR, and differential phase shift ΦDP) is proposed in this study. The spatial continuity of rain is guaranteed by introducing the radial B-spine filter and azimuthal Kalman filter, which helps to mitigate the impact of the random errors in ZDR and ΦDP. The approach is evaluated using a simulated experiment and two real cases observed by a mobile C-band and an operational S-band polarimetric radar in south China. The comparative results demonstrate that the proposed variational approach can correct attenuation more accurately than the conventional method using assumed linear relationships between specific attenuation and specific differential phase. The rainfalls derived from the DSD estimates based on this proposed approach agree well with the rain gauge measurements. It is also shown that the proposed method has a better performance than the existing variational retrieval and the composite estimator.