中南半岛及南海海域烟雾混合层积云的微观特性研究

Microscopic Properties of Smoke Polluted Stratocumulus over Indo-China Peninsula and the South China Sea

中南半岛地区生物物质燃烧活动使其成为东南亚烟雾气溶胶的高值区,排放的烟雾可以传播到南海海域,影响当地层积云的微观特性和降水活动,进而对气候产生影响。本文利用2007—2019年CALIPSO和CloudSat卫星数据筛选了190个烟雾气溶胶与层积云混合的个例,其中中南半岛等陆地上空(代表陆地)的烟雾混合层积云为88个,南海海域(代表海洋)的烟雾混合层积云为102个。基于个例的研究发现:相对于海洋上的烟雾混合层积云,陆地上的烟雾混合层积云中云的液态粒子数浓度(Number concentration of liquid water drops,LNC)、液态粒子有效半径(Geometric mean radius of liquid water drops,LER)和液态水含量(Liquid water content,LWC)的值都更高。与清洁层积云相比,烟雾气溶胶主要通过半直接效应影响海洋上的层积云,而主要作为云凝结核(Cloud condensation nuclei,CCN)通过间接效应影响陆地上的层积云。当气溶胶光学厚度(Aerosol optical depth,AOD)≤0.6时,海洋上烟雾混合层积云内Twomey效应发挥主导作用,而陆地上烟雾混合层积云内反Twomey效应发挥主导作用;当AOD处于0.6~1.2时,烟雾混合层积云的半直接效应发挥主导作用。本文的研究对中南半岛和南海海域的气溶胶与云的相互作用机制有重要参考意义,并为改进模式结果提供理论支持。

The biomass burning in Indochina Peninsula makes it a high value area of smoke aerosol in Southeast Asia.The emitted smoke can spread to the South China Sea,affecting the microphysical properties of local stratocumulus and precipitation activities,and then affecting the climate.Using CALIPSO and CloudSat satellite data from 2007 to 2019,this paper screens 190 cases of smoke aerosol mixing with stratocumulus,including 88 over Indo-China Peninsula(representing continental)and 102 over the South China Sea(representing marine).Based on the case study,it is found that in contrast to the marine smoke polluted stratocumulus,the number concentration of liquid water drops(LNC),geometric mean radius of liquid water drops(LER)and liquid water content(LWC)in continental smoke polluted stratocumulus are all higher.Compared with clean stratocumulus,smoke aerosol affects marine stratocumulus mainly through semi-direct effect,while smoke aerosol affects continental stratocumulus mainly through indirect effect as cloud condensation nuclei(CCN).When Aerosol Optical Depth(AOD)≤0.6,the Twomey effect plays a dominant role in marine smoke polluted stratocumulus,while the anti-Twomey effect plays a dominant role in continental smoke polluted stratocumulus.When AOD is between 0.6 and 1.2,the semi-direct effect of smoke polluted stratocumulus plays a dominant role.This study has important reference significance for the mechanism of aerosol-cloud interaction over Indochina Peninsula and the South China Sea,and provides theoretical support for the improvement of model results.