Convective and Microphysical Characteristics of Extreme Precipitation Revealed by Multisource Observations Over the Pearl River Delta at Monsoon Coast

Abstract

Extreme precipitation is an issue of worldwide concern, but its microphysics remain elusive. The convective and microphysical characteristics of extreme precipitation features (EPFs) in a monsoon coastal area (South China) are investigated mainly using 2‐year observations from a dual‐polarization radar and distrometers. The EPFs are accompanied by a broad range of convective intensity, and categorized into the “intense”, “moderate”, and “weak” convection accounting for 17.3%, 48.6% and 34.1% of the total population, respectively. The EPFs with weaker convection show weakened size sorting and less breakup of large raindrops, but a larger ratio of liquid water path to ice water path and more prominent coalescence warm‐rain process. All the three categories are dominated by the coalescence in the liquid‐phase processes, and have much more populous raindrops than the “continental” with a mean size larger than the “maritime” regime. These results improve our understanding of extreme precipitation from the microphysical perspective.

Extreme Precipitation Produced by Relatively Weak Convective Systems in the Tropics and Subtropics

“…Yu et al. (2022) reported that warm‐rain process is still very important in contributing to extreme precipitation in strong convective systems. Overall, the downward increase of drop size (indicated by reflectivity) below the freezing level of WeEPEs is much greater than that of InEPEs.…”

“…Some extreme rainfall events are accompanied by relatively warm cloud tops, lower radar echo tops, and little lightning activity (Gochis et al., 2015; Petersen, Carey, et al., 1999; Rasmussen & Houze, 2012; Smith et al., 2000; Tsuji et al., 2020). Also, warm‐type rain or relatively weak convection contributes a significant fraction of heavy rainfall over certain regions, for example, the Korean Peninsula (Sohn et al., 2013), Japan (Hamada & Takayabu, 2018) and Pearl River Delta in southern China (Yu et al., 2022). Such kind of storms occur over land in mid‐latitudes infrequently, but when they do occur, they can be devastating (Petersen, Carey, et al., 1999; Zipser & Liu, 2022).…”

“…Overall, strong convection contributes more than 50% of the total rainfall (Xu & Zipser, 2012) and the very rainy events (100 mm hr −1 ) over most global land areas (Wang & Tang, 2020). However, extreme convection (99.9th convective intensity) seems not a necessary condition for extreme precipitation (99.9th rainrate), and they have a relatively low overlapping fraction, for example, ∼30% over the United States and southern China (Gingrey et al., 2018; Yu et al., 2022) and mostly less than 10% over land in the tropics (Hamada et al., 2015).…”

“…On the other hand, weaker convective systems can also produce heavy precipitation through active warm‐rain processes (Hamada et al., 2015; Liu & Zipser, 2009; Sohn et al., 2013; Yu et al., 2022; Zipser & Liu, 2022) or orographic precipitation enhancement (Shige et al., 2013; Yamamoto et al., 2017). Some extreme rainfall events are accompanied by relatively warm cloud tops, lower radar echo tops, and little lightning activity (Gochis et al., 2015; Petersen, Carey, et al., 1999; Rasmussen & Houze, 2012; Smith et al., 2000; Tsuji et al., 2020).…”

Multiscale Perspectives on an Extreme Warm-Sector Rainfall Event over Coastal South China

“…The recent dual polarization upgrade of the operational weather radars in coastal South China has provided an opportunity to analyze the microphysical characteristics of precipitation over the coastal areas of South China, such as the rainband of Typhoon Nida [43], two consecutive mesoscale convective systems (MCSs) leading to a maximal rainfall accumulation of 451 mm on 11 May 2014 [29], the record-breaking rainfall event of 7 May 2017 influencing the megacity of Guangzhou [37], and an early summer event with coexisting frontal and warm-sector heavy rainfall [44]. Two case studies [29,37] and a statistical analysis focusing on extreme precipitation over coastal South China [45] consistently suggested that the extreme precipitation could be accompanied by a variety of convective intensities (i.e., the strength of mixed-phase processes) ranging from weak to intense, and has much more populous raindrops than the "continental" regime with a mean size larger than the "maritime" regime. However, the understanding of microphysical processes leading to the generation of extreme precipitation worldwide is still far from complete.…”