Long-range transport of Saharan dust and chemical transformations over the Eastern Mediterranean
Long-range transport of Saharan dust and chemical transformations over the Eastern Mediterranean
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DOI：
10.1016/j.atmosenv.2016.06.041
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发表时间：
2016-09-01
影响因子：
5
通讯作者：
Gerasopoulos, E.
中科院分区：
文献类型：
--
作者：
Athanasopoulou, E.;Protonotariou, A.;Gerasopoulos, E.
选取了2009年冬季、2010年深秋和2011年夏季撒哈拉沙漠沙尘暴爆发的3个不同季节（4-6天），研究了沙尘入侵东地中海（EM）的化学足迹和老化过程。应用模型系统（PMCAMx，WRF和GEOS-CHEM）和方法被认为能够再现沙尘生产，远程运输和化学转化的EM，协同使用天气模式分析，光学深度检索，后轨迹，表面和卫星气溶胶测量。沙尘负荷高，在冷期事件和轻得多，在夏季，当运输主要是在自由对流层。在所有情况下，沙尘都来自西北部和/或西撒哈拉沙漠，并从西部/西南部到达EM。敏感性试验是沙尘输送对EM上空气溶胶化学成分影响的基础，并显示出对钙的巨大影响（每日最大值2-5 μ g m（-3）的70-90%），其在地表水平的梯度沿沙尘路径每沿着100 km约为-10%。对于冷期的情况下，这个值也可以被认为是类似的灰尘消散率，因为羽垂直向下延伸到表层。有趣的是，EM上的表面颗粒硝酸盐浓度受到接近的灰尘负荷的影响，表现出最高值（高达6 μ g m（-3））和最大的灰尘分数（约100 μ g m（-3））。70%，夏季。这归因于高大气温度和日照下硝酸的形成增强，其被碳酸盐尘埃颗粒吸收，并由于海洋沉积率低和降水稀少而有效累积。发现尘埃颗粒上形成的硫酸盐微不足道（与氨和/或海盐快速反应），而当计算时空平均值时，尘埃和海盐对钠的影响大致相等。(C)2016爱思唯尔有限公司版权所有。
Three recent Saharan dust outbreaks during different seasons (4-6 days in winter of 2009, late autumn of 2010 and summer of 2011) are selected in order to study the chemical footprint and aging processes of dust intrusions over the Eastern Mediterranean (EM). The applied model system (PMCAMx, WRF and GEOS-CHEM) and methodology are found competent to reproduce dust production, long-range transport and chemical transformations over the EM, with the synergistic use of synoptic patterns analysis, optical depth retrievals, back-trajectories, surface and satellite aerosol measurements. The dust loads were high during the cold period events and much lighter during summertime, when transport was mainly in the free troposphere. In all cases, dust originated from the northwest and/or west Saharan desert and reached the EM from the west/southwest. Sensitivity runs underlie the effect of dust transport on the chemical constituents of aerosols over the EM and show a large impact on calcium (70-90% of maximum daily values 2-5 mu g m(-3)), with its gradient at surface level being around -10% per 100 km along the dust pathway. For the cold period cases, this value can also be considered analogous to the dust dissipation ratio, because the plume is vertically extended down to the surface layers. Interestingly, the surface particulate nitrate concentrations over the EM are reversely affected by the approaching dust loads, exhibiting the highest values (up to 6 mu g m(-3)) and the largest dust fraction (ca. 70%) during summertime. This is attributed to the enhanced nitric acid formation under high atmospheric temperature and insolation, its uptake onto the carbonate dust particles, and their effective accumulation, due to low deposition rates over the sea and scarce precipitation. Sulfate formation onto dust particles is found insignificant (rapid reaction with ammonia and/or sea-salt), while the influence of dust and sea-salt on sodium, when spatio-temporal averages are calculated, is approximately equal. (C) 2016 Elsevier Ltd. All rights reserved.