Analysis Of Convective And Microphysical Characteristics Of Extreme Precipitation With Increasing Rainfall Extremity Over The Pearl River Delta

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-yr dualpolarization radar observations,variations of convective and microphysical characteristics of extreme precipitation features(EPFs)with increasing rainfall extremity over a monsoon coastal region 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” convectionand “weak”convection,respectively,while that of the “moderate” convection remains about 50%.The higher rainfall extremity is accompanied by statistically significant increases in ice and liquid water contents,indicates a slight increase in the contribution of mixed-phase and ice-phase microphysical processes to the increasing rainfall extremity.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 with the increasing rainfall extremity.To ensure that the conclusion is robust,two sensitivity experiments are added.Sensitivity experiments on the definition of EPFs including thresholds in selecting area of composite radar reflectivity and connected pixes of extreme rain rates lead to changes on the EPFs’ sizes and the fraction of convection with different intensities.But the general conclusions remain unchanged and robust.