**6. Conclusions**

An epic flood event occurred in southern China from 27 August to 1 September 2018, with a maximum accumulative rainfall of 1394.6 mm recorded at Gaotan station. Multi-observations including reanalysis data, soundings, gauges, disdrometers, and polarimetric radars were used to comprehensively analyze this extreme precipitation event. Based on the reanalysis and gauge data, the synoptic environment and precipitation pattern were investigated. The DSD time series, the mass weighted diameter *Dm*, and normalized intercept parameter *Nw* of Huidong and Zhuhai stations were derived to achieve a better understanding of the precipitation microphysics. It was found that the depression coupled with land–sea interaction and orographic enhancement kept providing moisture to Guangdong province, leading to the extreme rainfall on 29 at Doumen station and on 30 August at Gaotan station. Although both locations are under the same synoptic system, the DSD observed at Huidong station showed a higher number concentration at smaller drop size and lower number concentration at larger drop size compared with the Zhuhai station. This is likely due to the stronger collision caused by sea–inland orographic effect near the Huidong station, which is similar to the microphysical signatures observed by polarimetric radars at Gaotan and Doumen rain regions. Future study is needed to reveal the mechanism of the sea–inland orographic effect on the precipitation microphysics. In addition, the radar based QPE results show that the rainfall algorithms have great influence on the accuracy. Extra work is required to improve local radar rainfall estimates in order to further help with the severe weather warning operations.

**Author Contributions:** Y.M. carried out the detailed analysis. H.C. and G.N. supervised the work. Y.M. and H.C. drafted the manuscript. G.N., V.C., and Y.G. reviewed and edited the manuscript. W.Z. collected the data and provided comments on this study. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the National Natural Science Foundation of China under Grants 41705018, 41575036, and 51679119, and the National Key Research and Development Program of China under Grant 2018YFA0606002.

**Acknowledgments:** The authors would like to thank Qiulei Xia for the help with creating Figure 1. The radar and rain gauge data were provided by China Meteorological Administration (CMA).

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
