Microphysical and Polarimetric Radar Signatures of an Epic Flood Event in Southern China

Yu Ma,Yabin Gou,V Chandrasekar,Haonan Chen,Wenjuan Zhang,Guangheng Ni

doi:10.3390/rs12172772

Abstract

An extremely heavy rainfall event hit Guangdong province, China, from 27 August to 1 September 2018. There were two different extreme rain regions, respectively, at the Pearl River estuary and eastern Guangdong, and a record-breaking daily precipitation of 1056.7 mm was observed at Gaotan station on 30 August. This paper utilizes a suite of observations from soundings, a gauge network, disdrometers, and polarimetric radars to gain insights to the two rainfall centers. The large-scale meteorological forcing, rainfall patterns, and microphysical processes, as well as radar-based precipitation signatures are investigated. It is concluded that a west-moving monsoon depression played a critical role in sustaining the moisture supply to the two extreme rain regions, and the combined orographic enhancement further contributed to the torrential rainfall over Gaotan station. The raindrop size distributions (DSD) observed at Zhuhai and Huidong stations, as well as the observed polarimetric radar signatures indicate that the rainfall at Doumen region was characterized by larger raindrops but a lower number concentration compared with that at Gaotan region. In addition, the dual-polarization radars are used to quantify precipitation intensity during this extreme event, providing timely information for flood warning and emergency management decision-making.

Highlights

Torrential rainfall events are one of the most severe disasters around the world [1,2]
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
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

Summary

Introduction

Torrential rainfall events are one of the most severe disasters around the world [1,2]. The extreme rainfall and induced floods, landslides, debris flows gravely threaten life and property. The precipitation microphysics such as raindrop size distribution (DSD) serves as a fundamental bridge in deriving radar quantitative precipitation estimation (QPE) algorithms, which is critical for improving the accuracy of precipitation estimation and predictions [3,4]. A better understanding of precipitation microphysics and accurate quantitative precipitation estimation for extreme rain are important for flood warning and emergency management decision-making. A record-breaking daily precipitation of 1056.7 mm was observed at Gaotan station on 30 August This heavy rainfall caused catastrophic floods in many cities such as Huizhou, Shantou, Zhuhai, affecting more than 1 million people, causing directed financial losses around USD 144 million (https://www.thepaper.cn/newsDetail_forward_2404157). A recent study has shown that extreme precipitation shows an increasing trend in south China during the last several decades [9], which highlights the importance of accurate precipitation measurement and modeling

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