Macro‐ and Microphysical Characteristics of Extreme Hourly Precipitation Over the Pearl River Delta on the Monsoon Coast (South China)

Abstract

AbstractIn this study, the Extreme Hourly Precipitation Areas (EHPAs) of three extreme levels (i.e., between the 95th and 99th percentiles, between the 99th and 99.9th percentiles, beyond the 99.9th percentile) in the Pearl River Delta over South China are identified; then the related events and associated Convective Cores (CCs) are tracked, and their macro‐and‐microphysical characteristics are analyzed using multi‐year dual‐polarization radar observations. Results show that >90% of EHPAs are smaller than 10 km2, and 65%–75% of EHPA events last only one hour. They tend to be more localized and persist longer with increasing hourly‐precipitation extremity. The EHPAs overlap with the CCs during 50%–64% of the EHPAs' life span. Their occurrence frequencies are nearly quadrupled after the monsoon onset over South China Sea (SCS), with a major (secondary) peak at about 1400 LST (0600 LST) in the diurnal variations. The CCs are non‐linear shaped with about 65% being meso‐γ‐scale and embedded within mostly meso‐β or α‐scale 20 dBZ regions. The CCs generally contain active warm‐rain processes and about 70% possess moderate‐to‐intense mixed‐phase microphysical processes. The ratios of ice water path to liquid water path are about 0.37, and coalescence dominates (about 68%) the liquid‐phase processes. The average size of raindrop is slightly larger than the “maritime‐like” regime and the average concentration is much higher than the “continental‐like” regime. These CCs' characteristics roughly resemble those of the convection producing extreme instantaneous precipitation, except for a larger horizontal scale and less evident variations with the increasing hourly‐precipitation extremity.