人为气溶胶的直接辐射效应及其对南亚冬季风的影响

运用区域气候模式RegCM4.0(Regional Climate Model Verson 4.0)耦合入一个化学过程,对硫酸盐、黑碳、有机碳这3种人为气溶胶的时空分布特征和直接辐射效应进行了数值模拟,进而研究了气溶胶对南亚冬季风的影响。结果表明:光学厚度和地表短波辐射强迫的时空变化可能主要受硫酸盐气溶胶的影响。在南亚夏季风向冬季风转换时期和南亚冬季风盛行时期,大气层顶和地表的负短波辐射强迫分布与气溶胶分布基本一致,地表辐射强迫强度绝对值比大气层顶辐射强迫强度绝对值大得多。相关分析和合成分析表明:在南亚夏季风向冬季风转换时期和南亚冬季风盛行时期,南亚人为气溶胶主要分布区中的气溶胶柱浓度含量与南亚冬季风的建立和强度有反相关关系。这与气溶胶吸收太阳辐射,从而引起气温和位势高度的变化有关。

Direct Radiative Effects of Anthropogenic Aerosols and Their Effects on the South Asian Winter Monsoon

The spatial-temporal distribution and direct radiative effect of three anthropogenic aerosols (sulfate, black carbon, and organic carbon) were simulated by using the regional climate model RegCM4.0 (Regional Climate Model verson 4.0) coupled with a chemistry module. Results from our investigation of the effect of aerosols on the South Asian winter monsoon show that the temporal and spatial changes in optical depth and surface short wave radiative forcing may be caused primarily by the sulfate aerosol. In the transition period between the South Asian summer and winter monsoons and during the prevailing South Asian winter monsoon, the distributions of negative short wave radiative forcing at the top of the atmosphere and at the surface are nearly consistent with the distribution of the aerosols. The absolute value of the intensity of the radiative forcing at the surface is much greater than its intensity at the top of the atmosphere. Correlation and composite analyses show that the aerosols' column burdens in the main distribution area of anthropogenic aerosols in South Asia is negatively correlated with the onset and intensity of the South Asian winter monsoon in the transition period between the South Asian summer and winter monsoons and during the prevailing South Asian winter monsoon. These effects may be attributed to the fact that aerosols absorb solar radiation, thereby inducing the changes in temperature and geopotential height.