Seasonal characteristics of tropical marine boundary layer air measured at the Cape Verde Atmospheric Observatory
Seasonal characteristics of tropical marine boundary layer air measured at the Cape Verde Atmospheric Observatory
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DOI：
10.1007/s10874-011-9206-1
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发表时间：
2010-12-01
影响因子：
2
通讯作者：
Wallace, D. W. R.
中科院分区：
文献类型：
--
作者：
Carpenter, L. J.;Fleming, Z. L.;Wallace, D. W. R.
对热带大气的观测对于了解空气质量、大气氧化能力和气候的全球变化至关重要，但在热带地区进行长期观测的人员不足。前三年全球气象组织/全球大气观测网佛得角大气观测站Humberto Duarte Fonseca提供的气象、痕量气体和微粒数据（2006年10月至2009年9月）（CVAO; 16 A度51' N，24 A度52' W），沿着的起源和路径的空气质量到达站使用NAME扩散模型和模拟的灰尘沉积使用COSMO-MUSCAT灰尘模型。观测结果表明，撒哈拉沙漠的沙尘在冬季有很强的影响，超微米气溶胶和铁铝微粒的影响最大。沙尘模式的结果匹配的大小和每日变化的沙尘事件，但在该地区的CVAO低估了测量的气溶胶光学厚度（AOT），因为其他气溶胶的贡献。NAME模型还捕捉到了沙尘事件，使人们相信它有能力正确识别该地区的气团来源和路径。对收集的粉尘样品的溶解实验表明，可溶性铁和铝之间的相关性很强，测得的溶解度在高大气粉尘浓度较低。CVAO的精细模式气溶胶含有大量的非海盐成分，包括二羧酸、甲磺酸和脂肪胺，所有这些都被认为是海洋来源的。海洋的影响也很明显，全年存在的碘和一氧化溴（IO和BrO），与IO建议主要局限于表面几百米，但BrO以及混合在边界层。增强的CO2和CH 4和贫氧浓度是附近的西北非洲沿海上升流地区海气交换的标志。远距离迁移导致源自北美的空气中臭氧-3和人为非甲烷碳氢化合物的水平普遍较高。臭氧/一氧化碳比率在相对新鲜的欧洲空气中最高（高达0.42）。在空气中严重影响撒哈拉沙漠的灰尘的O-3/CO比低至0.13，可能表明O-3吸收灰尘。氮氧化物（NOx和NOy）在冬季的浓度通常较高，而空气质量的来源主要来自非洲。春季/夏季OH和HO 2的最大浓度分别为9 × 10（6）分子cm（-3）和6 × 10（8）分子cm（-3），表明该地点的光化学活性很高。主要光解源后，在这个地区的HOx预算的最重要的控制IO和BrO化学，丰富的甲醛，和吸收HOx气溶胶。
Observations of the tropical atmosphere are fundamental to the understanding of global changes in air quality, atmospheric oxidation capacity and climate, yet the tropics are under-populated with long-term measurements. The first three years (October 2006-September 2009) of meteorological, trace gas and particulate data from the global WMO/Global Atmospheric Watch (GAW) Cape Verde Atmospheric Observatory Humberto Duarte Fonseca (CVAO; 16A degrees 51' N, 24A degrees 52' W) are presented, along with a characterisation of the origin and pathways of air masses arriving at the station using the NAME dispersion model and simulations of dust deposition using the COSMO-MUSCAT dust model. The observations show a strong influence from Saharan dust in winter with a maximum in super-micron aerosol and particulate iron and aluminium. The dust model results match the magnitude and daily variations of dust events, but in the region of the CVAO underestimate the measured aerosol optical thickness (AOT) because of contributions from other aerosol. The NAME model also captured the dust events, giving confidence in its ability to correctly identify air mass origins and pathways in this region. Dissolution experiments on collected dust samples showed a strong correlation between soluble Fe and Al and measured solubilities were lower at high atmospheric dust concentrations. Fine mode aerosol at the CVAO contains a significant fraction of non-sea salt components including dicarboxylic acids, methanesulfonic acid and aliphatic amines, all believed to be of oceanic origin. A marine influence is also apparent in the year-round presence of iodine and bromine monoxide (IO and BrO), with IO suggested to be confined mainly to the surface few hundred metres but BrO well mixed in the boundary layer. Enhanced CO2 and CH4 and depleted oxygen concentrations are markers for air-sea exchange over the nearby northwest African coastal upwelling area. Long-range transport results in generally higher levels of O-3 and anthropogenic non-methane hydrocarbons (NMHC) in air originating from North America. Ozone/CO ratios were highest (up to 0.42) in relatively fresh European air masses. In air heavily influenced by Saharan dust the O-3/CO ratio was as low as 0.13, possibly indicating O-3 uptake to dust. Nitrogen oxides (NOx and NOy) show generally higher concentrations in winter when air mass origins are predominantly from Africa. High photochemical activity at the site is shown by maximum spring/summer concentrations of OH and HO2 of 9 x 10(6) molecule cm(-3) and 6 x 10(8) molecule cm(-3), respectively. After the primary photolysis source, the most important controls on the HOx budget in this region are IO and BrO chemistry, the abundance of HCHO, and uptake of HOx to aerosol.