Multi-data Comparison And Numerical Simulation Study On The Cloud-radiation Characteristics Over Global Land Monsoon Region

The global land monsoon region is one of the most densely populated regions in the world.Limited by observation methods in the past,it is difficult to have an overall and objective study of cloud-radiation and its simulation.Therefore,using new satellite data to study the properties of clouds and their radiation in the global land monsoon region,and improving the simulating skills of climate models on the clouds,all have important significance.This paper focuses on the characteristics of clouds and radiation in the global land monsoon region.And then based on this conclusions,further evaluated the model simulation skills,especially the new version of CMIP6 model.The conclusions of the study are as follows:1.Climatic Characteristics of Cloud Radiative Forcing in Global lamd Monsoon RegionWe used different satellite products from different satellite sensors to give the characteristics of cloud-radiation in the global monsoon region The results show that,similar to the distribution of precipitation,the global monsoon region is also a large value area of cloud-radiation,and the cloud-radiation shows similar characteristics to precipitation that increase in summer and decrease in winter.Although there are some differences in the total cloud amount by different satellite data in the mean state,different satellite products can still give more consistent seasonal variability in the total cloud amount.Cloud Sat can reveal more detailed characteristics of the vertical structure of the cloud.And other satellite products can only provide the top-level information of the cloud.2.Long-term trends and interannual variability of cloud-radiation in the global land monsoon regionWe use different satellite products from different satellite data to analyze the seasonal variability and long-term trends of cloud-radiation in the global monsoon region,and the connections and differences in different sub-monsoon regions were also given.The results show that the interannual variability of the total cloud amount in the global monsoon region is uneven,and differences are found between the interannual variability distribution and the interannual variability distribution of precipitation.The interannual variability of the total cloud amount given by different satellite products has strong data dependence.For long-term trends of cloud,Satellite products show that the long-term trend of total cloud cover has an inflection point on the start of 21 st century.Prior to the 21 st century,the total cloud amount and radiative forcing in the global monsoon region showed a downward trend.After the 21 st century,the weaken trend of the total cloud amount has been suspended,and the monotonous trend of cloud amount has strong regional characteristics.3.Radiative Forcing and Cause of biaes of Clouds in the Global Monsoon Region Simulated by AMIP ModelsCombined with the previous conclusions,we used reanalysis data and satellite observation data,to study the simulation skills of cloud-radiation in three sets of Chinese climate model using AMIP experiments.And compared the data form five models of CMIP5 and CMIP6,found how the new models have improved in cloudradiation simulation,and further found the attribution of model simulation skills.The study found that: Compared with observation and reanalysis data,the simulation of cloud-radiation in each model is lower than observation,and the CMIP6 model have less improves in the simulation of cloud-radiation.It seems that the simulation biaes of the cloud vertical structure is caused by the simulation biaes of the vertical dynamic structure.Further research found that even in similar low-and middle-level dynamic structures,the models still did not give similar cloud-radiation characteristics to the reanalyzed data.4.Characteristics of stratiform Cloud over the East of Tibetan Plateau Simulated by Two Versions of the FGOALS2 Climate System ModelOn the east of Tibetan Plateau,is covered by stratiform clouds in winter time.A reasonable simulation of these clouds over the leeside of the Tibet Plateau remains a challenge for the current state-of-the art climate models.In this study,we compared the Cloud radiation forcing and other cloud properties and their radiative forcing at the top of the atmosphere from two LASG/IAP climate system models,Atmospheric Model Intercomparison Project(AMIP)of Flexible Global Ocean–Atmosphere–Land Systems2 and g2(FGOALS-s2 and FGOALS-g2),and observations from Satellite data.It was found that both models underestimated the strength of shortwave cloud forcing,cloud water path,and cloud fraction over Eastern China.Such bias in the simulation of stratiform clouds is related to weak lower tropospheric stability and insufficient lowlevel moisture.In addition,the overestimated average cloud top height in FGOALS-g2 was explained as an unrealistic updraft,which produced stronger vertical moisture transports over the east of Tibetan Plateau.