Aerosols from biomass burning over the tropical South Atlantic region: Distributions and impacts
Aerosols from biomass burning over the tropical South Atlantic region: Distributions and impacts
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南大西洋热带地区生物质燃烧产生的气溶胶：分布和影响
DOI：
10.1029/96jd00717
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发表时间：
1996
影响因子：
--
通讯作者：
N. Blake
中科院分区：
文献类型：
--
作者：
B. Anderson;W. Grant;G. Gregory;E. Browell;J. Collins;G. Sachse;D. Bagwell;C. Hudgins;D. Blake;N. Blake
1992年9月21日至10月26日，美国国家航空航天局（NASA）进行了全球对流层实验（GTE）赤道-大西洋附近运输和大气化学（TRACE A）考察，以调查造成季节性南大西洋对流层臭氧最大值的因素。在这些飞行中，与北半球观测和同一地区在雨季记录的测量结果相比，在热带南大西洋的偏远地区观测到的细气溶胶（0.1-3.0 μm）数量密度增加了大约10倍，在邻近的大陆地区则增加了更多。化学和气象分析以及目视观测表明，这些增强的主要来源是发生在巴西中北部和非洲东南部草原地区的生物质燃烧。在巴西和非洲，这些火灾的气溶胶(N)排放比相对于CO （dN/dCO）分别为22.5±9.7和23.6±15.1 cm−3十亿分之一体积(ppbv)−1。随后，南大西洋副热带反气旋周围的对流加上逆时针气流将这些气溶胶分布到遥远的南大西洋对流层。我们计算出，生物质燃烧产生的稀释烟雾在大陆地区平均使光学深度增加了10倍，在南大西洋中部使该参数增加了50%；这些变化对应于晴空条件下热带草原和海洋的净降温估计分别高达25和2.4 W m - 2。在海洋上空，我们的分析表明，持续存在的东大西洋海洋层积云内的CCN浓度被下沉的雾霾层夹带所改变，可能会显著增加云的反照率，从而导致额外的地表辐射冷却，其幅度可能比气溶胶颗粒本身直接消除太阳辐射所造成的冷却更大。
The NASA Global Tropospheric Experiment (GTE) Transport and Atmospheric Chemistry Near the Equator-Atlantic (TRACE A) expedition was conducted September 21 through October 26, 1992, to investigate factors responsible for creating the seasonal South Atlantic tropospheric ozone maximum. During these flights, fine aerosol (0.1–3.0 μm) number densities were observed to be enhanced roughly tenfold over remote regions of the tropical South Atlantic and greater over adjacent continental areas, relative to northern hemisphere observations and to measurements recorded in the same area during the wet season. Chemical and meteorological analyses as well as visual observations indicate that the primary source of these enhancements was biomass burning occurring within grassland regions of north central Brazil and southeastern Africa. These fires exhibited fine aerosol (N) emission ratios relative to CO (dN/dCO) of 22.5 ± 9.7 and 23.6 ± 15.1 cm−3 parts per billion by volume (ppbv)−1 over Brazil and Africa, respectively. Convection coupled with counterclockwise flow around the South Atlantic subtropical anticyclone subsequently distributed these aerosols throughout the remote South Atlantic troposphere. We calculate that dilute smoke from biomass burning produced an average tenfold enhancement in optical depth over the continental regions as well as a 50% increase in this parameter over the middle South Atlantic Ocean; these changes correspond to an estimated net cooling of up to 25 W m−2 and 2.4 W m−2 during clear-sky conditions over savannas and ocean respectively. Over the ocean our analyses suggest that modification of CCN concentrations within the persistent eastern Atlantic marine stratocumulus clouds by entrainment of subsiding haze layers could significantly increase cloud albedo resulting in an additional surface radiative cooling potentially greater in magnitude than that caused by direct extinction of solar radiation by the aerosol particles themselves.