Characteristics Of Summer Raindrop Size Distribution In Asia Pacific Region And Its Applications To Quantitative Rainfall Estimations

It has been adequately demonstrated that the knowledge of Raindrop size distribution(DSD)is essential for a better understanding of microphysical processes in the generation of precipitation particles as well as a fundamental quantity in radar meteorology and other remote sensing applications.Numerous studies have revealed that DSD varies among different precipitation types,different climate regimes and different terrains.Thus it is of great significance to study the DSD characteristics in some key areas.In this research,we investigated the DSD in Asia-Pacific region,where there are multiple weather systems such as Subtropical High,East Asian Summer Monsoon,Mei-Yu front,Tropical cyclones.The results can be divided into the following four parts:(1)Three subregions named south western Pacific(SWP),west western Pacific(WWP)and north western Pacific(NWP)were separated for a comparative study of the variability of DSD in Western Pacific.The DSD characteristics of six different rain rates and two rain types(convective and stratiform)were studied.Histograms of normalized intercept parameter log₁₀(N_w)and mass-weighted mean diameter D_mindicated largest log₁₀(N_w)values in WWP while largest D_mvalues in SWP,and the convective clusters in three regions could be indentified between maritime-like and continental-like.(2)Western and Eastern parts of the Monsoon rainband were separated for a comparative study of the DSD variability.,The DSD characteristics of six rain rate classes and two rain categories(convective and stratiform)were studied.The spectral width of Western part is larger than Eastern part,which is caused by the stronger convection activities in Western part.The aerosols could inhibit warm rain process while enhance cold rain process in Western part.Overall,the small and midsize drops jointly dominate the rainfall in EASM season.Western part has larger mass-weighted mean diameter D_mwhile smaller normalized intercept log₁₀(N_w)than Eastern part,and the convective clusters of Western part could be identified roughly maritime-like due to moisture transport from tropical ocean,while that of Eastern part could be identified between continental-like and maritime-like.Cross validation of GPM rainfall products are implemented based on surface disdrometer observations.DPR algorithm manifests better performance over sea than land areas of EASM rainband.(3)Observations of the DSD of typical typhoon systems over Asia-Pacific region are implemented,it is found that the precipitation of typhoon is dominated by warm cloud process.Because of the high humidity of underlying surface and the low cloud bottom,it is beneficial to the further development of warm cloud.The precipitation of typhoon is mainly composed of stratiform precipitation,but the particle number concentration of convective precipitation is greater than that of stratiform precipitation,and the content of small raindrops in stratiform rain is more than that of convective rain.Compared with monsoon precipitation,typhoon precipitation has higher droplet concentration and smaller droplet size.(4)By studying all the oceanic precipitation samples over Asia-Pacific region,the overall D_m-N_wdistribution for Asia-Pacific region satisfied...