Retrieval Of Ice Clouds Microphysical Properties At The SACOL Site

Ice cloud is one of the most widely distributed cloud types both in China and globally.Because of its unique physical and optical properties,ice cloud plays an important and special role in the radiation budget.Understanding and recognizing the microphysical properties of ice clouds is of great significance for studying the effects of ice clouds on climate change.Ka-Band Zenith Radar(KAZR),which has been deployed at the Semi-Arid Climate and Environment Observatory of Lanzhou University(SACOL)since July 2013,has been continuously operated for many years.We compare the microphysical properties(ice effective particle size(Dge)and ice water content(IWC)derived from three algorithms which are traditional algorithms(Microbase),Z-IWC-T relationship(Hogan)and KAZR-MPL retrieval algorithm.And then we compute and examine radiative fluxes using each set of cloud properties as input to a radiative transfer model,compare the top-of-atmosphere(TOA)radiative fluxes to the satellite measured to assess the impact of differences in the microphysical quantities of different ice clouds on radiation.The main conclusions are as follows:(1)The microphysical parameters of the ice cloud have obvious seasonal and daily variation characteristics.The ice water content and effective particle size in the warm season are generally higher than the cold season,and the maximum height is higher.The maximum monthly mean value of ice water content and effective particle size appeared in September,and the minimum value appeared in December.In summer,the ice water content and effective particle size in clouds were larger,and their peak positions were higher,followed by spring and autumn,and the lowest in winter.Ice clouds appear more frequently at night than in daytime.There are three peaks of ice cloud ice water content and effective particle size in one day,which are before and after sunrise,afternoon and sunset respectively.(2)The ice water content retrieved by three different inversion methods shows a unimodal distribution.The ice water content was mainly concentrated in the range of0.01-10 mg/m~3 and the corresponding ice water content in the maximum probability is basically concentrated in the vicinity of 0.1mg/m~3.However there are some differences between the data concentration degree and the peak probability of different algorithms.The effective particle size distribution obtained by the three methods is quite different.The effective particle size of the ice crystals inversion by the Microbase algorithm is unimodal,and the data is mainly concentrated in the small particle radius region of 0-100?m.The KAZR-MPL algorithm has a wider range of particle distributions,with two peaks at 40?m and 96?m,respectively.(3)Using the results of three different microphysical properties,the long and short wave radiation fluxes at the top of the atmosphere are calculated through the Fu-Liou radiation transfer model.The results show that the long-wave radiation fluxes calculated by different cloud microphysical characteristics are in good agreement with the satellite observation data.The average error is 5.04%,and the correlation coefficients are all greater than 0.6.Compared with the observed long-wave radiation,the Hogan algorithm considering the temperature effect has better simulation effect,the correlation coefficient is larger,and the root mean square error is smaller.The short-wave radiation are smaller than the observed values in the case of cloud,and the maximum error can reach 24.61%.The short-wave radiant flux simulated by the traditional empirical algorithm is closest to satellite observation,and its root mean square error is significantly reduced compared with other methods.The short-wave heating rate of ice cloud is positive,while the long-wave radiation is cooling in the upper part of the cloud and heating in the lower part of the cloud.The net cloud radiative heating rate is positive with a value of 4 W/m~2.