Quantification of topographic venting of boundary layer air to the free troposphere
Quantification of topographic venting of boundary layer air to the free troposphere
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DOI：
10.5194/acp-4-497-2004
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发表时间：
2003-10
影响因子：
6.3
通讯作者：
S. Henne;M. Furger;S. Nyeki;M. Steinbacher;B. Neininger;S. Wekker;J. Dommen;N. Spichtinger;A. Stohl;A. Prévôt
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文献类型：
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作者：
S. Henne;M. Furger;S. Nyeki;M. Steinbacher;B. Neininger;S. Wekker;J. Dommen;N. Spichtinger;A. Stohl;A. Prévôt
摘要。研究了阿尔卑斯深谷上空大气边界层（ABL）向自由对流层（FT）热驱动气流的净垂直气团输出。目前，在全球化学运输模式（GCTMs）中，山地地形上方污染物的垂直出口表现不佳，需要量化。气团预算是利用在阿尔卑斯深谷获得的飞机观测资料计算的。结果表明，在良好天气条件下，平均每天垂直输出3次山谷气团。在白天，本研究调查的山谷类型可以作为一个有效的“气泵”，向上输送污染物。河谷内坡风系统对污染物的再分配起着重要作用。山区的氮氧化物排放被有效地注入到大气中。这可以提高它们的臭氧（O3）生产效率，从而影响对流层污染预算。一旦上升到阿尔卑斯山上空的FT，污染物就会被天气气流水平输送，并受到欧洲污染出口的影响。前方轨迹研究表明，在晴朗的天气条件下，阿尔卑斯山上空的气团主要有两条路径。向北移动的气团在整个对流层柱中混合，并进一步向东输送到亚洲。在地中海上空的副热带高压系统内向南下降的气团。
Abstract. Net vertical air mass export by thermally driven flows from the atmospheric boundary layer (ABL) to the free troposphere (FT) above deep Alpine valleys was investigated. The vertical export of pollutants above mountainous terrain is presently poorly represented in global chemistry transport models (GCTMs) and needs to be quantified. Air mass budgets were calculated using aircraft observations obtained in deep Alpine valleys. The results show that on average 3 times the valley air mass is exported vertically per day under fair weather conditions. During daytime the type of valleys investigated in this study can act as an efficient "air pump" that transports pollutants upward. The slope wind system within the valley plays an important role in redistributing pollutants. Nitrogen oxide emissions in mountainous regions are efficiently injected into the FT. This could enhance their ozone (O3) production efficiency and thus influences tropospheric pollution budgets. Once lifted to the FT above the Alps pollutants are transported horizontally by the synoptic flow and are subject to European pollution export. Forward trajectory studies show that under fair weather conditions two major pathways for air masses above the Alps dominate. Air masses moving north are mixed throughout the whole tropospheric column and further transported eastward towards Asia. Air masses moving south descend within the subtropical high pressure system above the Mediterranean.