Multi-decadal aerosol variations from 1980 to 2009: a perspective from observations and a global model
Multi-decadal aerosol variations from 1980 to 2009: a perspective from observations and a global model
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DOI：
10.5194/acp-14-3657-2014
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发表时间：
2014-01-01
影响因子：
6.3
通讯作者：
Zhao, X. -P.
中科院分区：
文献类型：
--
作者：
Chin, Mian;Diehl, T.;Zhao, X. -P.
利用戈达德化学气溶胶辐射和传输 (GOCART) 模型以及多个卫星传感器和可用地面网络的观测结果，分析了 1980 年至 2009 年不同陆地和海洋区域的气溶胶变化和趋势。排除火山影响较大的时间段，污染土地区域的气溶胶光学深度（AOD）和表面浓度通常随人为排放而变化，但这种关联的程度可能会因自然气溶胶（尤其是灰尘）的存在而减弱。在这项研究的 30 年期间，气溶胶水平下降幅度最大的是欧洲，其中 AOD 平均下降了 40-60%，表面硫酸盐浓度下降了 3-4 倍。相比之下，东亚和南亚的AOD有所增加，但亚洲沙尘气溶胶水平相对较高，降低了AOD与污染物排放趋势之间的相关性。在主要沙尘源区，模型分析表明，撒哈拉和萨赫勒地区沙尘排放量变化主要受近地表风速变化驱动，而中亚地区沙尘排放量变化主要受地表湿度变化影响。北大西洋热带沙尘流出区以及巴巴多斯和迈阿密接收点沙尘的减少趋势与北大西洋海面温度的升高密切相关。这种温度升高可能会导致北非上空风速的降低，从而减少粉尘排放，以及热带北大西洋上空降水的增加，从而增强运输过程中的除尘效果。尽管一些主要大陆源区存在显着趋势，但模型计算的全球年平均AOD显示过去三十年陆地和海洋变化不大，因为不同陆地区域的相反趋势在全球平均中相互抵消，而大片公海的变化可以忽略不计。这凸显了对气溶胶及其气候影响进行区域尺度评估的必要性，因为全球尺度的平均值可能会掩盖重要的区域变化。
Aerosol variations and trends over different land and ocean regions from 1980 to 2009 are analyzed with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and observations from multiple satellite sensors and available ground-based networks. Excluding time periods with large volcanic influence, aerosol optical depth (AOD) and surface concentration over polluted land regions generally vary with anthropogenic emissions, but the magnitude of this association can be dampened by the presence of natural aerosols, especially dust. Over the 30-year period in this study, the largest reduction in aerosol levels occurs over Europe, where AOD has decreased by 40-60% on average and surface sulfate concentrations have declined by a factor of up to 3-4. In contrast, East Asia and South Asia show AOD increases, but the relatively high level of dust aerosols in Asia reduces the correlation between AOD and pollutant emission trends. Over major dust source regions, model analysis indicates that the change of dust emissions over the Sahara and Sahel has been predominantly driven by the change of near-surface wind speed, but over Central Asia it has been largely influenced by the change of the surface wetness. The decreasing dust trend in the North African dust outflow region of the tropical North Atlantic and the receptor sites of Barbados and Miami is closely associated with an increase of the sea surface temperature in the North Atlantic. This temperature increase may drive the decrease of the wind velocity over North Africa, which reduces the dust emission, and the increase of precipitation over the tropical North Atlantic, which enhances dust removal during transport. Despite significant trends over some major continental source regions, the model-calculated global annual average AOD shows little change over land and ocean in the past three decades, because opposite trends in different land regions cancel each other out in the global average, and changes over large open oceans are negligible. This highlights the necessity for regional-scale assessment of aerosols and their climate impacts, as global-scale average values can obscure important regional changes.