The Characteristics Of Ice Clouds Distribution And The Relationship With Aerosols Over China Region Based On MODIS And CALIOP

The role of ice clouds in radiative forcing and climate change is still very uncertain.In the current study of global climate change,the ice cloud radiative forcing effect is an urgent problem.Studies have shown that aerosols can become ice nuclei,provide favorable conditions for the occurrence and development of ice clouds,and have an impact on their radiation characteristics,but the specific mechanisms still need further study.The use of satellite data can detect the characteristics of ice clouds over a long time.With the growing maturity of satellite observation methods,it has become possible to study the effects of aerosols on ice clouds.Therefore,in order to study the influence of aerosols on ice clouds,we first calculated the distribution characteristics and changing trends of ice clouds in China for 15 years.From January 2002 to December 2016,we used the Terra MODIS level III atmosphere data.The product data(MOD08_M3)performed the horizontal distribution and seasonal variation of ice cloud probability,effective particle radius,optical thickness,and ice-level cloud water path in China(72°E-136°E,0°N-550°N).Then,this article uses the MODIS sensor air quality data product(MYD08_M3)equipped on the Aqua satellite from January 2007 to December 2016 to study the horizontal distribution characteristics of ice cloud parameters and aerosol optical thickness in China and calculate their Pearson correlations.Coefficients and selected areas of high aerosol optical thickness:northwestern regions and northern regions are discussed.Finally,using the aerosol data of the CALIPSO satellite from January 2007 to December 2016,we verified the occurrence frequency of aerosols with ice heights above 5 km.It was found that although the aerosol optical thickness in North China is larger,it is higher than 5 km.Aerosols mainly distribute in the northeast region,while in northern China there are less high aerosols,further illustrating the effects of aerosols on ice clouds.The main findings are as follows:(1)In terms of the distribution of ice clouds in China,the horizontal distribution and seasonal variation of ice cloud characteristics are related to the occurrence of East Asian monsoon and strong convective weather.During the fifteen years,the probability of occurrence of ice clouds showed an upward trend,and the seasonal variation law was obvious.High-value areas appeared in the northeast of the Qinghai-Tibet Plateau;the horizontal distribution of ice-particles' effective particle radius gradually increased from southwest to northeast,and ice clouds were effective for fifteen years.The particle radius shows a decreasing trend,but it appears seasonally at higher latitudes.The optical thickness of ice clouds is roughly the same as the horizontal and seasonal variations of ice-water pathways,showing a decreasing trend from southeast to northwest.The overall seasonal variation is obvious.There is no obvious increase in the decreasing trend.(2)In terms of the relationship between ice clouds and aerosols in China,the optical thickness of aerosols is positively correlated with the probability of occurrence of ice clouds,negatively correlated with the effective particle radius of ice clouds.This article focuses on the relationship between ice clouds and aerosols in two typical regions in the northwest and northern regions.The optical thickness of aerosols in the Tarim Basin and the Qaidam Basin in northwestern China shows a significant positive correlation with the probability of occurrence of ice clouds,and there is a significant negative correlation with the effective radius of ice clouds.The major areas related to aerosols and ice clouds in northern China are concentrated in the northeastern region.The correlation of optical thickness,ice-level cloud-water path and aerosol optical thickness of ice clouds in the northwest and north regions shows that negative correlations in the desert region have positive correlations in areas with better water vapor conditions,suggesting that aerosols have an effect on ice.The influence of the cloud optical thickness and the ice-level cloud-water path is related to the water vapor and the thermal conditions of the underlying surface.