Influence Of Different Ice Crystals Scattering Models On Retrieval Of Ice Cloud Parameters And Estimation Of Surface Shortwave Radiation

The cloud plays an important role in the global energy and water cycle,and is an indispensable part of the earth-atmospheric system.From the global scale,cloud cover and some insignificant changes in cloud optical and microphysical parameters may have a significant impact on the climate system.Therefore,the study of spatial and temporal distribution characteristics of cloud,cloud optical and microphysical parameters has great significance to the correct understanding of cloud radiation properties,and the impact on surface radiation and climate change.We could use satellite remote sensing to know spatial and temporal distribution characteristics of cloud,and combined with radiative transmission theory to retrieval the cloud optical and microphysical parameters.However,the retrieval accuracy of ice cloud and multi-layer cloud by using remote sensing still has great uncertainty.This will lead to subsequent errors in estimating surface solar radiation.In this paper,using the optical and microphysical parameters(optical thickness,particle radius,etc.)of the Himawari-8 cloud product during December 2016-November 2017,we extracted the full-range ice cloud and multi-layer cloud parameters.At the same time,we analyze their spatial and temporal distribution characteristics.According to the analysis,the average monthly cloud cover of ice cloud and multi-layer cloud ranged from large to small in summer,winter,spring and autumn.The occurrence frequency of ice cloud is highest in the range of 10oN~10oS,and most of the areas can be more than 45%.The occurrence frequency of multi-layer cloud is highest near the equator,with most of the area between 25%and 35%.In order to grasp the influence of different ice crystal models on the retrieval of single-layer ice cloud and double-layer cloud parameters and the estimation of surface short-wave radiation,the RSTAR radiative transfer model is used as analyze the ice crystal model,satellite observed radiance and surface short-wave radiation.The sensitivity of different cloud parameters,solar zenith angles,and satellite observed angles are also analyzed.On this basis,based on the double layer cloud cover condition observed by CALIPSO,a look-up table method(LUT)is used to estimate the retrieval error of cloud parameters by the double-layer clouds with different phase and ice crystal models,and to estimate the radiation of the short-wave radiation on the surface.The main conclusions are as follows:(1)Under the assumption of a single ice cloud,the calculated radiance of different cloud phases decreases with the increase of the solar zenith angle,while the surface short-wave radiation decreases rapidly and increases with the increase of surface albedo.The radiance calculated by different ice crystal models decreases with the increase of the solar zenith angle,and increases with the increase of the satellite zenith angle.The surface shortwave radiation decreases sharply with the increase of the solar zenith angle.The radiance of water cloud calculated with different effective particle radius increases with the increase of optical thickness,while the d surface short-wave radiation decreases.(2)Under the assumption of a double-layer cloud,for the same radiance observed by the satellite:When the ice crystal model is spherical,the optical thickness difference between the water cloud and the ice cloud obtained by the retrieval is small,so that the calculated surface short-wave radiation difference is also small.The relative error is 1.91%;When the ice crystal model is hexagonal,the optical thickness difference between the water cloud and the ice cloud is very large.When the radiance is 214.1 W/m~2.?m.sr,the maximum relative error is 56.31%.To explore the influence of different ice crystal models on the retrieval of cloud parameters and estimation of surface short-wave radiation,which helps to deepen our understanding of the role of cloud in the global climate change.Accurately grasping the retrieval error caused by the double-layer is also the same.At the same time,our research can provide reference for improving the algorithm of satellite retrieval of cloud parameters.