Three-dimensional Cloud Variations And Their Radiative Effects Based On Multiple Active And Passive Satellite Observations

Cloud are visible polymers composed of liquid or ice water and suspended in the atmosphere.It regulate the climate system by affecting solar shortwave radiative transmission,atmospheric and surface longwave radiative emission,and precipitation,dominating radiative balance,water cycle,and earth-atmosphere system interaction.The impacts of cloud on climate change are determined by both of its vertical structure and microphysical properties,which disturb the vertical radiative heating and cooling rate of the atmosphere,further affecting the regional radiation budget,precipitation process,and monsoon circulation.Previous studies mainly based on passive satellite and ground-based observations.However,vertical information about cloud and aerosol has not been adequately considered due to observation limitations.This limits the scientific understanding of the three-dimensional?3D?characteristics of aerosol-cloud changes,interactions and their climate impacts.Here,by combining active and passive satellite observations and radiative transfer model,this study investigate the mechanism of vertical aerosol-cloud interaction,3D cloud variation and its radiative influence,as well as the climate impacts?monsoon feedback?of cloud vertical structure.Further,the scientific problems of 3D aerosol-cloud-radiation-monsoon interaction and its climate impacts are discussed in detail.Therefore,this study has carried on the exploration specifically in the following aspects:?1?Vertical aerosol interaction with water cloud.Impacts of environmental conditions on vertical aerosol-cloud interaction have been not evaluated suitably,generating the significant uncertainty in the evaluation of aerosol climate effect.It is found that difference in atmospheric water vapor content,aerosol absorption level and vertical distribution determine different interaction processes,which can explain significant seasonal and regional differences over South Asia.Further,combined with active and passive multiple satellite observations,vertical water aerosol-cloud interaction result in radiative forcing of-0.34±0.40 and 1.11±0.08 W/m² during monsoon and non-monsoon seasons.?2?Vertical aerosol interaction with ice cloud.Although ice clouds are widely distributed in the upper atmosphere?about 30%?,ice cloud-aerosol interaction mechanism is still unclear due to the limited observation and understanding of ice cloud itself.Depending on the high sensitivity of the CALIPSO observation to vertical ice cloud characteristics,we find that aerosols lead to the reduction of ice cloud particles and water content in South Asia,and reaching saturation at AOD=1.Furthermore,these phenomena of ice clouds are attributed to the competition with each other through homogeneous nucleation and heterogeneous nucleation with the influence of water vapor,atmospheric stability and aerosol type.?3?Impact of 3D cloud change on the rapidly warming of the Tibetan Plateau?TP?.The warming rate of the TP has been more than three times of the global average speed in recent decades,but the specific reasons are not clear.It is found that the average low-level cloud fraction and geometric thickness decreased by about 4.2%and 130m in the past decade over the TP based on the CALIPSO and CouldSat 3D satellite observations.This change has led to an increase in instantaneous surface shortwave radiation about29.7 W/m²,which is an order of magnitude larger than that caused by CO_2.The 3D cloud variations may be the main reason,which promotes the rapidly warming of the TP.?4?Feedback of 3D cloud characteristics on monsoon.The large-scale monsoon circulation regulates the distribution,growth and phase transformation of the global cloud,but the feedback mechanism of cloud to the monsoon circulation and its climate impact remain unresolved.We found that the clouds caused atmospheric radiative heating of 1 K/d and 0.4 K/d during summer and winter over East Asia,respectively,which were mainly derived from cloud longwave radiative heating.Further,vertical cloud-induced radiative heating mainly result from high,stratiform and stratocumulus cloud systems,and is conducive to the strengthening of the East Asian monsoon circulation,promoting summer and winter winds of 1.8 m/s and 0.5 m/s,respectively.