气溶胶影响亚洲夏季风机理的数值研究

利用NCEP/NCAR （National Centers for Environmental Prediction/National Center for Atmospheric Research）2001-2010年再分析资料，检验了全球气候系统模式CESM中大气模块CAM （Community Atmosphere Model）对亚洲夏季风和大气热源的模拟能力。结果显示，模式可以再现亚洲夏季风和大气热源的主要特征。通过敏感试验探讨人为气溶胶影响亚洲夏季风的机理，分析、讨论了气溶胶引起的非均匀加热的变化对辐散风和无辐散风强度的影响，在机理上解释了亚洲夏季风减弱的原因。结果表明，人为气溶胶浓度的升高使东亚夏季风强度在中国东南地区、中南半岛北部和印度半岛北部减弱。而中国东南部季风的减弱促使中国内陆降水减少，沿海降水增多。进一步分析人为气溶胶浓度升高的作用发现，其改变了大气热源的分布，造成阿拉伯海、孟加拉湾和中国南海大气热源增强，中国东部地区和中南半岛大气热源减弱，其中气溶胶通过影响凝结潜热来改变大气热源，主要是对对流过程的影响。此外，大气热源分布的变化改变了季风区的热力结构，使中国东南地区、中南半岛北部的加热减弱，从而减少了全位能的产生，使得全位能向辐散风的转换减小，辐散风减弱；同时，中国东南部、中南半岛北部季风由于辐散风向无辐散风转换的减弱，无辐散风减弱，最终导致了夏季风强度的减弱。而且，人为气溶胶对亚洲夏季风的影响主要通过大气热力和动力过程的响应产生作用。

A numerical study of the mechanism of aerosols' effect on Asian summer monsoon

In this paper, we use the NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) 2001-2010 reanalysis data to evaluate the simulation capability of atmospheric module CAM (Community Atmosphere Model) in the global climate system model CESM for Asian summer monsoon and atmospheric heat sources. The results show that the model can reproduce the main features of the Asian summer monsoon and atmospheric heat sources. The mechanism of aerosol climate effects on the Asian summer monsoon is investigated by sensitive experiments. By analyzing the influence of the inhomogeneous heating changes induced by aerosols on the divergent wind and rotational wind components, the reason for the Asian summer monsoon weakening is explained. The results indicate that the increase in anthropogenic aerosols weakens the Asian summer monsoon in southeastern China, northern Indochina Peninsula and Indian peninsula. The weakened monsoon in southeastern China has led to decrease in inland precipitation and increase in coastal precipitation. Further analysis finds that the anthropogenic aerosols increases result in changes in atmospheric heat sources, which enhance in the Arabian Sea, the Bay of Bengal and the South China Sea and weaken in the eastern China and Indochina peninsula. The aerosols mainly change the atmospheric heat source by affecting latent heat. The changes in latent heat are largely affected by convection process. On the other hand, the changes in atmospheric heat sources alter the thermal structure over the monsoon region and weaken atmospheric heat sources in southeastern China and northern Indochina Peninsula. The weakened atmospheric heat sources reduce the generation of the total potential energy and subsequent transform from total potential energy to divergent winds, resulting in weakened divergent winds. At the same time, the transform from divergent winds to rotational winds decreases in southeastern China and northern Indochina peninsula, which eventually leads to the weakening of the summer monsoon. Moreover, anthropogenic aerosols affect the Asian summer monsoon mainly through affecting atmospheric heat sources and dynamic processes.