CloudSat-based Precipitating And Non-precipitating Cloud Properties Over East Asian And South Asian Monsoon Area

Not only clouds are playing an important role in the energy balance,atmospheric circulation and climate changes,but also closely relevant to the precipitation mechanism and precipitation efficiency.Clouds can be generally classified as precipitating clouds(PCs)and non-precipitating clouds(non-PCs).Studying the characteristics of PCs and non-PCs,as well as their possible differences is significant to understand the precipitation mechanism and improve the climate model.As the first satellite with active millimeter-wave radar to observe and study cloud distribution,cloud vertical structure,cloud radiation characteristics and precipitation information on a global scale,Cloud Sat shows a great advantage in observing the PCs.In this thesis,three-year(Mar 2007 to Feb 2010)cloud products of Cloud Sat satellite and precipitation data of TRMM satellite were used to analyze the characteristics and differences of PCs and non-PCs over the East Asian monsoon area(EMA)and the South Asian monsoon area(SMA).A number of cloud properties of PCs and non-PCs,such as precipitation seasonality,macroscopical properties(i.e.cloud layers,cloud thickness,cloud top height,the maximum height of frozen precipitation,and cloud type),the vertical distribution of radar reflectivity,and microphysical properties of non-PCs(i.e.cloud optical thickness,effective radius,liquid water path,and ice water path),were investigated in this study.The main conclusions are as follows:(1)There was evident difference between PCs and non-PCs in occurrence frequencies,cloud thickness and cloud type over EMA and SMA.With respect to their vertical properties,PCs and non-PCs were dominated by single-layer cloud over EMA,and PC occurrence frequency decreased from May to its lowest value in September,then increased after October.However,it showed an opposite trend with a peak value in summer,and single-layer and double-layer cloud are equally important over SMA.About cloud thickness,PCs varied with seasonally significantly over EMA,with its maximum in summer and minimum in winter,but did not reflect seasonal pattern over SMA.Clouds over SMA usually developed much higher than over EMA.Cloud thickness of Non-PCs were normally blow 5 km over both EMA and SMA,but PCs can developemuch deeper.Deep convective cloud(Dc)and nimbostratus(Ns)were the main types of PCs.Ns dominated all types of PCs over EMA except for summer when Dc played a main role.In SMA,however,Dc was the main PCs type throughout the year.Non-PCs was dominated by high cloud(cirrus)and medium clouds(altostratus/altocumulus).(2)For the vertical distribution of radar reflectivity,PCs were mainly distributed below 8 km,with radar reflectivity in the range of-15~15 d Bz.Based on radar reflectivity profile,PCs radar reflectivity enhanced alone with the height initially and then gradually weakened.Furthermore,particles grew faster in SMA and their particle accumulation belt was wider compared to EMA.The vertical distribution of the PCs over EMA was similar to Ns except summer which was more like DC.While PC vertical distribution was like DC in SMA,and PCs Seasonal changes were not as significantly as EMA.Compared to PCs,non-PCs radar reflectivity is smaller and in a higher altitude.(3)There were some differences in non-PC microphysical properties between EMA and SMA.The annual average of cloud optical depth over SMA was greater than EMA with nearly 50%,but they mainly distributed below 10 over these two monsoon areas and did not exist the obvious seasonal variation.On the contrary,the effective radius,liquid and ice water path over SMA were significantly larger than EMA.In both aeras,the liquid and ice water path were concentrating in100g/m~2 and 300g/m~2,respectively.