**Lei Ji 1, Haonan Chen 2,3,\*, Lin Li 1,4, Baojun Chen 5, Xian Xiao 1, Min Chen <sup>1</sup> and Guifu Zhang <sup>6</sup>**


Received: 12 May 2019; Accepted: 19 June 2019; Published: 21 June 2019

**Abstract:** Fourteen-month precipitation measurements from a second-generation PARSIVEL disdrometer deployed in Beijing, northern China, were analyzed to investigate the microphysical structure of raindrop size distribution and its implications on polarimetric radar applications. Rainfall types are classified and analyzed in the domain of median volume diameter *D*<sup>0</sup> and the normalized intercept parameter *Nw*. The separation line between convective and stratiform rain is almost equivalent to rain rate at 8.6 mm h−<sup>1</sup> and radar reflectivity at 36.8 dBZ. Convective rain in Beijing shows distinct seasonal variations in log10 *Nw*–*D*<sup>0</sup> domain. X-band dual-polarization variables are simulated using the *T*-matrix method to derive radar-based quantitative precipitation estimation (QPE) estimators, and rainfall products at hourly scale are evaluated for four radar QPE estimators using collocated but independent rain gauge observations. This study also combines the advantages of individual estimators based on the thresholds on polarimetric variables. Results show that the blended QPE estimator has better performance than others. The rainfall microphysical analysis presented in this study is expected to facilitate the development of a high-resolution X-band radar network for urban QPE applications.

**Keywords:** Northern China; raindrop size distribution (DSD); microphysical processes; quantitative precipitation estimation (QPE)
