Impacts of Asian summer monsoon on seasonal and interannual variations of aerosols over eastern China
Impacts of Asian summer monsoon on seasonal and interannual variations of aerosols over eastern China
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亚洲夏季风对中国东部气溶胶季节和年际变化的影响
DOI：
10.1029/2009jd012299
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发表时间：
2010-04-02
影响因子：
4.4
通讯作者：
Li, Jianping
中科院分区：
文献类型：
--
作者：
Zhang, Li;Liao, Hong;Li, Jianping
中国位于一个大型季风区；与亚洲夏季风相关的气象场变化可以影响中国东部气溶胶的运输、沉积和化学反应。本文应用NASA/GEOS - 4同化气象数据驱动的全球三维戈达德地球观测系统（GEOS）化学输运模型（GEOS - Chem），量化了东亚夏季风对中国东部气溶胶季节和年际变化的影响。在夏季风季，位于40°E - 135°E范围内的四条强跨赤道气流通道为中国带来了来自南半球的清洁空气。这些通道具有稀释中国东部气溶胶浓度的作用。与此同时，与夏季风相关的雨带在6 - 8月期间从中国东南部向北方移动，导致大量气溶胶湿沉降。因此，夏季中国东部气溶胶浓度最低。没有季节变化的敏感性研究表明，亚洲夏季风可以使中国东部（110°E - 120°E, 20°N - 45°N）的表层PM2.5（直径小于2.5μm的颗粒）气溶胶浓度平均降低约50-70%，因为7月的浓度与1月的浓度相比。我们还比较了1998年弱季风年和2002年强季风年的模拟pm2.5浓度，假设这两年的模拟排放量相同。由于硫酸盐、硝酸盐、铵盐、黑碳、有机碳以及亚微米矿物粉尘和海盐，1998年6 - 8月弱季风年和中国东部地区表层pm2.5平均浓度比2002年强季风年高7.06μg m−3(44.3%),pm2.5柱负荷比2002年高25.1 mg m−2（73.1%）。因此，在中国东部地区，1998 - 2002年夏季气溶胶光学深度的差值估计约为0.7。这些结果对了解中国东部气溶胶的空气质量和气候效应具有重要意义。
China is located in a large monsoon domain; variations in meteorological fields associated with the Asian summer monsoon can influence transport, deposition, and chemical reactions of aerosols over eastern China. We apply a global three‐dimensional Goddard Earth Observing System (GEOS) chemical transport model (GEOS‐Chem) driven by NASA/GEOS‐4 assimilated meteorological data to quantify the impacts of the East Asian summer monsoon on seasonal and interannual variations of aerosols over eastern China. During the summer monsoon season, four channels of strong cross‐equatorial flows located within 40°E–135°E are found to bring clean air to China from the Southern Hemisphere. These channels have the effect of diluting aerosol concentrations in eastern China. In the meantime, rain belts associated with the summer monsoon move from southeastern to northern China during June–August, leading to a large wet deposition of aerosols. As a result, aerosol concentrations over eastern China are the lowest in summer. Sensitivity studies with no seasonal variations in emissions indicate that the Asian summer monsoon can reduce surface layer PM2.5(particles with a diameter of 2.5μm or less) aerosol concentration averaged over eastern China (110°E–120°E, 20°N–45°N) by about 50–70%, as the concentration in July is compared to that in January. We also compare simulated PM2.5concentrations in the weak monsoon year of 1998 with those in the strong monsoon year of 2002, assuming same emissions in simulations for these 2 years. Accounting for sulfate, nitrate, ammonium, black carbon, organic carbon, as well as submicron mineral dust and sea salt, surface layer PM2.5concentration averaged over June–August and over eastern China is 7.06μg m−3(or 44.3%) higher in the weak monsoon year 1998 than in the strong monsoon year 2002, and the column burden of PM2.5is 25.1 mg m−2(or 73.1%) higher in 1998 than in 2002. As a result, over eastern China, the difference in summer aerosol optical depth between 1998 and 2002 is estimated to be about 0.7. These results have important implications for understanding air quality and climatic effects of aerosols in eastern China.