Spatio-temporal Variations Of Aerosol Properties And Its Relationship With Cloud Parameters Over East China During 2000-2016

Cloud and aerosol are the important part of the gas system and plays an important role in the radiation budget.The Changes in aerosols and associated radiative forcing,and their impact on the climate system have been highly valued by the scientific community in the recent years due their large uncertainty factor.In recent decades,the rapid development of social economy in East China,aerosol particles emissions and production of secondary aerosol pollutants by photochemical reactions are also increasing,caused serious environmental and climate problems.Hence,it is important to study the temporal and spatial distribution of aerosols in this region,and understand the-aerosol-cloud interactions.In the present study,we examined the spatial and temporal variations in aerosol optical depth(AOD)at 550 nm and its relationship with various cloud parameters derived from the Moderate resolution Imaging Spectroradiometer(MODIS)sensor onboard Terra satellite over East China during 2000-2016.The detection results indicate that the pollution situation is more serious in the northern East China.High-value center appeared in Shandong Province and AOD value has been higher than 1.0.The Angstrom exponent that increases with AOD is opposite;to what would be the case if swelling of particles due to hygroscopic growth near cloudy areas played a major role in the MODIS data.We then analyzed the relationships between AOD and other cloud parameters,namely water vapor(WV),cloud effective radius(CER),cloud fraction(CF),cloud top temperature(CTT),and cloud top pressure(CTP).In the spatial correlation analysis,the correlation of AOD and CTP is similar with the changes of AOD and CTT and the correlation is negative in most regions.The spatial correlation between AOD-CER and AOD-CF meets the first indirect effect.The correlation coefficient is between-0.2-0.0.In the other regions,there was a counter-indirect indirect effect with a correlation coefficient of 0.6-0.8.This may be due to supersaturated aerosol particles in the atmosphere.In the temporal correlation analysis,AOD has increased over a period of 16 years.When it increases to 0.7,aerosol particles begin to compete for water vapor,and the large reduction of small cloud droplets allows the cloud to develop better,WV decreases,CER and CF increase,and CTP and CTT decrease simultaneously.During the year,the highest AOD value appeared in June,and November was the lowest in the whole year.During this process,monsoon and meteorological elements played a crucial role.It was found that May was a time node.Prior to May,AOD was negatively correlated with WV,CER,and CF,and positively correlated with CTP and CTT.After May,the phenomenon was just the opposite.