Microphysical Characteristics And Radiation Effects Of Different Cloud Types In East Asia

Clouds is one of the largest uncertainties to impact energy budget of earth-atmosphere system.it is also one of the main sources to be responsible for the uncertainties in weather and climate forecasting.Different cloud types with different macro and microphysical characteristics exhibit completely different radiation effects.The difference of radiation effects among different cloud types mainly depends on their microphysical characteristics and vertical structures.Therefore,based on the active satellite Cloud Sat/CALIPSO products and using RRTM and WRF models,we systematically carried out the related research work on the influence of cloud microphysical characteristics on cloud radiation effect.The research results are able not only to improve the current understanding of the microphysical characteristics and radiation effects of different cloud types,but also to provide the necessary research basis for further understanding the cloud-radiation feedback mechanism,It can also help to improve the cloud microphysical parameterize scheme in models.Specific contents and major conclusions are summarized as follows:Cloud water content(CWC),cloud liquid effective radius(LER),ice particle effective radius(IER)are extracted from Cloud Sat/CALIPSO Rail-by-Rail Cloud Classification Products(2B-CLDCLASS-LIDAR)and Microphysical Information Products(2B-CWC-RVOD)from 2007 to 2010,and these main microphysics characteristics of different cloud types are analyzed in East Asia.It is found that the vertical distribution of microphysical parameters of the same cloud type has no difference between the ocean and the land,but the magnitude is slightly larger over the ocean than over the land.The vertical distribution characteristics of CWC in different cloud types are basically the same,increasing first and then decreasing with height,but the probability distribution spectrum of CWC varies significantly with different cloud types,which the probability distribution spectrum of Cumulus is the widest(0-1000 mg.m^-3).IER varies greatly in vertical direction in different cloud types.The IER probability distributions of Nimbostratus,deep convective cloud and Cumulus are the widest(0-150?m)and Cirrus is the narrowest(35-100?m).The vertical distribution characteristics of LER in different cloud types are basically the same.The LER range of all cloud types is between 0-25?m,in which the probability distribution spectra of Altostratus,Cumulus,Nimbostratus and deep convective cloud are unimodal symmetrical.Using RRTM single-column radiation transfer model,the effects of different cloud microphysical changes on cloud radiation effects were studied through control variables method,and the single-column radiation effects of different types of clouds were quantitatively evaluated.The results show that the changes of cloud microphysical parameters mainly affect the solar shortwave radiation,while the infrared longwave radiation effects mainly depend on the cloud top height(temperature).The increase of effective radius and ice component in cloud water content results in the decrease of the absolute value of cloud shortwave radiation forcing,while the increase of cloud liquid water(ice)results in the increases of the absolute value of cloud shortwave radiation forcing.The influence of variations in cloud microphysical characteristics on the solar shortwave radiation forcing at the top of the atmosphere is greater than that on the surface.The solar shortwave radiation forcing of different cloud types at the top of the atmosphere has a consistent correspondence with cloud water paths.The larger the cloud water paths is,the greater the absolute value of the shortwave radiation forcing;While the infrared longwave radiation forcing at the top of the atmosphere corresponds to the cloud top height,the higher the cloud top height is,the greater the longwave radiation forcing.Based on the WRF model,two different methods of calculating the effective radius of cloud microphysical parameters are compared in a case study of heavy precipitation occurring in northeastern China in August 2012.The influence of different effective radius of hydrometeors on precipitation forecast is further analyzed.The results show that the effective radius of hydrometeors needs to be calculated accurately when the cloud microphysics scheme is coupled with the radiation parameterization scheme.Different effective radius can affect the radiation flux,especially the shortwave radiation flux.The variation of radiation flux affects the heating rate,causing change of regional precipitation.The overall geographical distribution of forecasted 24-hour cumulative rainfall is unaffected,but its rainfall changes.Compared with the method of simple calculating the effective radius as a function of temperature and underlying surface type,the precipitation forecasted by considering the characteristics of hydrometeors is more consistent with the observed results,indicating that the radiation transfer process has a certain effect on short-term precipitation.A more reasonable method of calculating effective radius can improve the ability of the model to surface precipitation forecast.