Atmospheric brown clouds: Hemispherical and regional variations in long-range transport, absorption, and radiative forcing
Atmospheric brown clouds: Hemispherical and regional variations in long-range transport, absorption, and radiative forcing
复制标题
DOI：
10.1029/2006jd008124
复制
发表时间：
2007-10-23
影响因子：
4.4
通讯作者：
Yoon, S. C.
中科院分区：
文献类型：
--
作者：
Ramanathan, V.;Li, F.;Yoon, S. C.
该研究利用卫星观测、全球同化气溶胶数据集、大气褐云观测站、蒙特卡罗气溶胶云辐射模式和区域化学传输模式（STEM-2K）来表征褐云的空间范围、区域和特大城市的大气褐云热点、化学成分和直接辐射强迫。它介绍了印度-亚洲-太平洋地区ABC观测站气溶胶观测和强迫的第一个年度周期。东亚、印度-恒河平原、印度尼西亚地区、南部非洲和亚马逊河流域是以人为气溶胶光学厚度（AOD）大于0.3和吸收AOD > 0.03为标准的区域热点。在这些热点以及在其他受污染的海洋区域，EC质量超过0.5 μ g m（-3），OC质量超过2 mg m（-）3，硫酸盐质量超过10 mg m（-3），从表面到3 km。棕色云也有很强的季节依赖性。在热带地区，季节依赖性是由旱季（北方热带地区为12月至2月，南半球热带地区为6月至8月）的污染积累造成的。在热带以外的地区，污染在夏季达到高峰。褐云问题并不局限于热带地区。在美国东半部和西欧，AOD超过0.2，吸收AOD超过0.02。棕色云也延伸到西太平洋，印度洋到达南纬60度和大西洋东部。中国和美国的SO2排放总量最大，而德国和英国的单位面积SO2排放量最大。EC和OC排放总量最大的是中国，而单位面积OC排放量最大的是印度。结果表明，印度和德国上空的TOA直接强迫最大。区域热点地区的地面年-日平均变暗量在-10 W m（-2）量级，特大城市热点地区的地面年-日平均变暗量在-20 W m（-2）量级。
The study uses satellite observations, global assimilated aerosol data sets, Atmospheric Brown Clouds (ABC) observatories, a Monte Carlo aerosol-cloud-radiation model and a regional chemical transport model (STEM-2K) to characterize the spatial extent of brown clouds, regional and megacity ABC hot spots, chemical composition and the direct radiative forcing. It presents the first annual cycle of aerosol observations and forcing from the ABC observatories in the Indo-Asia-Pacific regions. East Asia, Indo-Gangetic Plains, Indonesian region, southern Africa and the Amazon basin are the regional hot spots defined by the criteria that anthropogenic aerosol optical depths (AODs) should exceed 0.3 and absorbing AOD > 0.03. Over these hot spots, as well as in other polluted oceanic regions, the EC mass exceeds 0.5 mu g m(-3), the OC mass exceeds 2 mg m(-)3 and sulfate mass exceeds 10 mg m -3 from the surface to 3 km. The brown clouds also have strong seasonal dependence. In the tropics the seasonal dependence is driven by pollution accumulating during the dry seasons, December to February in Northern Hemisphere tropics and June to August in Southern Hemisphere tropics. In the extratropics the pollution peaks during the summer. The brown cloud problem is not restricted to the tropical regions. Over the eastern half of US and western Europe the AODs exceeds 0.2 and absorption AODs exceed 0.02. Brown clouds also extend well into the western Pacific Ocean, the Indian Ocean reaching as far south as 60 degrees S and the eastern Atlantic Ocean. The largest total SO2 emission occurs over China and US, while SO2 emission per unit surface area is maximum over Germany and England. The largest total EC and OC emissions occur over China, but the largest OC emission per unit surface area occur over India. As a result, the maximum negative annual mean TOA direct forcing is over India and Germany. The surface annual-diurnal mean dimming over the regional hot spots is of the order of -10 W m(-2) and -20 W m(-2) over megacity hotpots.