How Do the Convective and Microphysical Characteristics of Extreme Precipitation Over the Pearl River Delta at Monsoon Coast Vary With Increasing Rainfall Extremity?

Using 5-year dual-polarization radar observations, variations of convective and microphysical characteristics of extreme precipitation features (EPFs) with increasing rainfall extremity over a monsoon coastal region (Pearl River Delta; PRD) in South China are investigated through comparing three groups of EPFs (ER1, ER2, and ER3). The more extreme rainfall shows a notable increase and decrease in the fractions of "intense" convection and "weak" convection, respectively. The higher rainfall extremity is accompanied by statistically significant increases in ice and liquid water contents but a roughly equal fraction of coalescence in liquid-phase processes. While the raindrop size distributions of ER1 to ER3 similarly feature a mean size larger than "maritime-like" droplets and a concentration much higher than "continental-like" raindrops, the mean size and concentration of raindrops tend to increase slightly with the increasing rainfall extremity. Two sensitivity experiments on EFP definition confirm the robustness and representative of the above results. Extreme precipitation could induce flooding and severe hazards and may increase in the warming climate. It has recently been shown that extreme precipitation can be produced by very intense convection with presence of large solid precipitating particles such as graupel and hail, or by weak convection with much shorter vertical extension through rapid growth of many raindrops, or by moderate convection in between. However, we do not know well to what extent extreme precipitation overlaps with intense convection and how the convective and microphysical characteristics change with increasing rainfall extremity. To answer these questions, we use 5-year dual-polarization radar observations over a monsoon coastal region combined with distrometer observations, and comparatively analyze the convective and microphysical characteristics of rainfall with three different extreme levels. Results show that, with higher rainfall extremity, probability distribution of the extreme rainfall-producing convection tends to shift toward stronger convective intensity, producing larger liquid and ice water contents (significant at 0.01 confidence level) and also slightly higher concentration with larger mean size of raindrops. With more extreme rainfall, the extreme precipitation features tend to grow in horizontal size from the meso-& gamma;- to meso-& beta;-scaleOverlap between extreme precipitation and extreme convection increases substantially with more extreme rainfallEnhanced mixed-phase processes, larger liquid/ice water contents, slight changes in liquid-phase processes are with more extreme rainfall