Effects Of Synoptic Weather Patterns And Pollution On Microphysical Characteristics Of Precipitation In East And South China During Warm Season

Raindrop size distribution(DSD)is the basic microscopic physical properties of precipitation.Revealing the characteristics of Raindrop spectra in the eastern and southern coastal areas of China plays an important role in understanding the microphysical process of rainfall,improving the radar quantitative precipitation estimation and improving the microphysical parameterization scheme of the model.In this paper,the data from a two-dimensional video disdrometer(2DVD),a vertically pointing micro rain radar(MRR),and PM10 were collected during the OPACC 2014-2017 field campaign and the Cooperative Observation Test of South China monsoon/Typhoon heavy precipitation 2016-2017 field campaign.Combined with the principal component analysis method of oblique rotation T mode,the DSD characteristics of falling water of different weather types were studied,and the influence of air pollution on precipitation was discussed.Firstly,the observed rainfall is classified into convective,stratiform and shallow precipitation types,and the difference in microphysical statistical characteristics of precipitation between East and South China in warm season is analyzed quantitatively,revealing that the overall raindrop concentration in South China in convective precipitation is higher than that in East China,and stratiform precipitation in South China is composed of large particles with higher concentration.On this basis,the daily average 850 hPa height field of the 2014-2017 04-09 is divided into 5 circulation types objectively,revealing that the characteristics of raindrop spectrum under different weather types were greatly different,which were affected by factors such as water vapor and unstable energy.The first three type corresponds to the pre-Meiyu(Type 1),Meiyu(Type 2),post-Meiyu(Type 3)in East China,respectively corresponds to Pre-flood season in South China.Type fourth and fifth corresponds to WPSH(Type 4)and Typhoon(Type 5).It is found that relative humidity and convection instability have significant influence on precipitation,in which the high relative humidity in the WPSH weather pattern in East China affects the shallow precipitation and brings more small raindrops.During Meiyu and pre-Meiyu,the convection instability is weak and the concentration of large raindrops is low in East China.Finally,the distribution of particle pollution concentration in East and South China is classified by air quality observation data,and the statistical characteristics of precipitation DSD under different pollution concentrations are analyzed.The findings suggest that enhanced aerosol concentrations reduce the mean size of cloud droplets,suppressing coalescence,permitting more freezing of cloud droplets and associated latent heat release above the 0? isotherm,and enhancing the growth of large hail and cold-rain processes in convective precipitation.This is now known as the aerosol invigoration effect.The aerosol effect on stratiform precipitation is more complex.In the small particle size scale(<3 mm),enhanced aerosol concentrations can also suppress warm rain processes by reducing particle sizes and causing a narrow droplet spectrum that inhibits collision and coalescence processes.In the large particle size scale(>3 mm),aerosol invigorate stratiform precipitation from low pollution to high.The stratiform precipitation invigoration effect occur in the large particle size scale(>3 mm)from low pollution to moderate pollution.If the aerosol concentration is higher than moderate pollution,stratiform precipitation is reduced.The enhanced aerosol concentration inhibited the occurrence of precipitation and delayed the time of precipitation due to the competing results of aerosol radiation effects and microphysical effects.