Chemical characteristics of continental outflow over the tropical South Atlantic Ocean from Brazil and Africa
Chemical characteristics of continental outflow over the tropical South Atlantic Ocean from Brazil and Africa
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巴西和非洲热带南大西洋大陆流出物的化学特征
DOI：
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发表时间：
1996
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通讯作者：
A. Bachmeier
中科院分区：
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作者：
R. Talbot;J. Bradshaw;S. Sandholm;S. Smyth;D. Blake;N. Blake;G. Sachse;J. Collins;B. Heikes;B. Anderson;G. Gregory;H. Singh;B. Lefer;A. Bachmeier
本文通过对1992年9 - 10月热带南大西洋大气环流的海洋和大陆外流分类的分析，总结了热带南大西洋大气环流的化学特征。CO和CH 3Cl之间的正相关性和最小的增强C2Cl 4和各种氯氟烃（CFC）物种的空气包裹最近平流在南大西洋盆地强烈建议对流层化学的影响，从生物质燃烧对邻近的巴西和非洲大陆地区。将南大西洋海盆0.3至12.5公里高度的老化太平洋空气与老化海洋空气的成分进行比较表明，在当地旱季，长寿物种有可能积累。这可能相当于C2 H6增加了两倍，CO增加了30%，CH 3Cl增加了10%。一氧化氮和氮氧化物显着增强（高达十亿分之一的体积（ppbv））10公里以上的高度和相关性较差的CO和CH 3Cl。此外，中值混合比的NO和NOx基本上是相同的，在老年人的海洋和大陆外流的空气质量。看来，除了生物质燃烧，闪电或再循环的活性氮可能是一个重要的氮氧化物的对流层上部的来源。甲烷表现出一个单调的增加，从1690年至1720 ppbv的老年海洋和大陆外流的空气质量与高度。对流层上部的最大混合比往往与CO，CH 3Cl和CO2相关，这表明CH 4的贡献来自自然源。我们还认为，基于CH 4/CO的比例和各种碳氢化合物和CFC物种的关系，从生物质燃烧和北方半球的输入不太可能是主要来源的CO，CH 4，和C2 H6在老化的海洋空气。城市地区的排放量似乎是必要的，至少要考虑到甲烷和碳氢化合物的分布。在非洲和南美洲大陆的对流垂直输送加上大规模的环流的有效机制，输送生物质燃烧，城市和自然排放到对流层上部的南大西洋盆地。南大西洋盆地东部的缓慢沉降可能在建立和维持该地区长寿物种的垂直分布方面发挥重要作用。对流层上部CH 3 OOH/H2 O2比值大于1的常见现象表明，降水清除有效地去除了高度水溶性气体（H2 O2，HNO 3，HCOOH和CH 3COOH）和气溶胶在大陆上空的垂直对流输送。然而，在南大西洋上空，生物质燃烧产物，特别是水溶性物质和气溶胶粒子，在6公里以下的高度经常水平喷射。
The chemical characteristics of air parcels over the tropical South Atlantic during September – October 1992 are summarized by analysis of aged marine and continental outflow classifications. Positive correlations between CO and CH3Cl and minimal enhancements of C2Cl4 and various chlorofluorocarbon (CFC) species in air parcels recently advected over the South Atlantic basin strongly suggest an impact on tropospheric chemistry from biomass burning on adjacent continental areas of Brazil and Africa. Comparison of the composition of aged Pacific air with aged marine air over the South Atlantic basin from 0.3 to 12.5 km altitude indicates potential accumulation of long-lived species during the local dry season. This may amount to enhancements of up to two-fold for C2H6, 30% for CO, and 10% for CH3Cl. Nitric oxide and NOx were significantly enhanced (up to ∼1 part per billion by volume (ppbv)) above 10 km altitude and poorly correlated with CO and CH3Cl. In addition, median mixing ratios of NO and NOx were essentially identical in aged marine and continental outflow air masses. It appears that in addition to biomass burning, lightning or recycled reactive nitrogen may be an important source of NOx to the upper troposphere. Methane exhibited a monotonic increase with altitude from ∼1690 to 1720 ppbv in both aged marine and continental outflow air masses. The largest mixing ratios in the upper troposphere were often anticorrelated with CO, CH3Cl, and CO2, suggesting CH4 contributions from natural sources. We also argue, based on CH4/CO ratios and relationships with various hydrocarbon and CFC species, that inputs from biomass burning and the northern hemisphere are unlikely to be the dominant sources of CO, CH4, and C2H6 in aged marine air. Emissions from urban areas would seem to be necessary to account for the distribution of at least CH4 and C2H6. Over the African and South American continents an efficient mechanism of convective vertical transport coupled with large-scale circulations conveys biomass burning, urban, and natural emissions to the upper troposphere over the South Atlantic basin. Slow subsidence over the eastern South Atlantic basin may play an important role in establishing and maintaining the rather uniform vertical distribution of long-lived species over this region. The common occurrence of values greater than 1 for the ratio CH3OOH/H2O2 in the upper troposphere suggests that precipitation scavenging effectively removed highly water soluble gases (H2O2, HNO3, HCOOH, and CH3COOH) and aerosols during vertical convective transport over the continents. However, horizontal injection of biomass burning products over the South Atlantic, particularly water soluble species and aerosol particles, was frequent below 6 km altitude.