Effects Of Cloud Overlapping Parameters On The Simulated Total Cloud Fraction Over The Globe And East Asian Region

Cloud overlapping parameters(Vertical decorrelation length,Lcf)from CloudSat/CALIPSO was applied into Beijing Climate Center's GCM(BCC AGCM2.0)to diagnose its impact on the simulation of globe and East Asian region cloud fraction.(1)By comparing the climate simulation results obtained by constant Lcf of 2 km with those of the above retrieved Lcf in the model without a two-parameter cloud microphysical scheme,we found that the total cloud fraction was improved obviously by the satellite-based Lcf.After using satellite-based Lcf,the climate simulation result of the total cloud fraction was improved obviously,comparing with constant Lcf of 2 km.The error of global mean total cloud fraction between simulations and CERES(Clouds and the Earth's Radiant Energy System)satellite data was decreased by 1.6%in both winter and summer,of which the positive deviation of total cloud amount at tropical convection area and the negative deviation in subtropical region were significantly reduced.These helped to simulate the energy budget differences in different regions properly.In East Asia,using the satellite-based Lcf decreased the error of average total cloud fraction to the CERES by 1.8%(1.4%)in winter(summer).(2)Comparing the simulation results of global total cloud fraction in the model with a two-parameter cloud microphysical scheme with the CERES satellite data,it has been found that the satellite-based Lcf causes some changes.In winter,there are clear positive bias in the equator field and the mid-high latitudes land,and there are significant negative deviations in the mid-latitude ocean surface.In summer,there are positive deviations in the oceans on both sides of the equator,and negative deviations occurring on the mid-latitude ocean surface,especially in the Indian Peninsula and the Indian Ocean.In winter,the positive deviations around the equator and the Somali basin have decreased,while the negative deviations over the Sea of Japan,the South Australian basin,and the Chilean Strait also show a certain degree of reduction,vice versa in the summer.For East Asia region,after introducing the satellite-based Lcf,positive deviations in the Tibetan Plateau have been significantly reduced in the winter,while negative deviations in the Sea of Japan and Sichuan Basin have also been reduced to some extent.It can be seen that after introducing the satellite-based Lcf,the simulation results of the model are shifted in the correct direction.Totally,the Lcf from CloudSat/CALIPSO satellite data can improve the simulation of total cloud fraction and thus the accuracy of radiation field.In particular,the Lcf from CloudSat/CALIPSO satellite data in the model with a two-parameter cloud microphysical scheme can reduce the error of cloud fraction and it has positive significance for improving the simulation accuracy of the radiation field.