Abstract：
A declining trend in Indian summer monsoon precipitation (ISMP) in the latter half of the 20th century is a scientifically challenging and societally relevant research issue. Heavy aerosol loading over India is one of the key factors in modulating the ISMP. Using the state-of-the-state-of-the-art chemistry-climate model, ECHAM6-HAMMOZ, the impacts of South Asian anthropogenic sulfate aerosols on the Indian summer monsoon precipitation were investigated against: (1) 2010 La Niña (excess monsoon), (2) 2015 El Niño (deficit monsoon) in comparison to (3) normal monsoon 2016. Sensitivity simulations were designed with 48% enhancement in South Asian SO2 emissions based on a trend estimated from Ozone Monitoring Instrument (OMI) satellite observations during 2006-2017. The model simulations showed that sulfate aerosols reduce ISMP by 27.5%-43.3 %, while simulations without sulfate loading enhanced ISMP by 23% in 2010 La Niña and reduction by 35% in 2015 El Niño. This paper reports that sulfate aerosols loading over India reduce precipitation by aerosol-induced direct and indirect effects by inducing atmospheric cooling, weakening in the convection, and reduction in moisture transport to Indian landmass. This paper emphasizes the necessity of alternate use of energy to reduce sulfate aerosol emissions to solve water issues in South Asia.
摘要：
20世纪下半叶印度夏季风降水（ISMP）的下降趋势是一个具有科学挑战性且与社会相关的研究问题。印度上空的大量气溶胶负荷是调节ISMP的关键因素之一。使用最先进的化学气候模型，ECHAM6-HAMMOZ,南亚人为硫酸盐气溶胶对印度夏季风降水的影响进行了调查：（1）2010拉尼娜（过量季风），（2）2015年厄尔尼诺（赤字季风）与（3）2016年正常季风相比。根据2006-2017年臭氧监测仪（OMI）卫星观测的趋势，设计了敏感性模拟，南亚SO2排放量增加了48％。模型模拟表明，硫酸盐气溶胶可降低ISMP27.5%-43.3%，虽然没有硫酸盐负荷的模拟使2010年拉尼娜的ISMP增加了23%，2015年厄尔尼诺减少了35%。本文报道，印度上空的硫酸盐气溶胶负荷通过诱导大气冷却，通过气溶胶诱导的直接和间接效应减少了降水，在对流中减弱，并减少了向印度陆地的水分输送。本文强调了交替使用能源以减少硫酸盐气溶胶排放的必要性，以解决南亚的水问题。
