A mechanism for moistening the lower stratosphere involving the Asian summer monsoon
A mechanism for moistening the lower stratosphere involving the Asian summer monsoon
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DOI：
10.1002/qj.1999.49712555602
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发表时间：
1999-04
影响因子：
8.9
通讯作者：
A. Dethof;A. O'Neill;J. Slingo;H. Smit
中科院分区：
文献类型：
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作者：
A. Dethof;A. O'Neill;J. Slingo;H. Smit
本研究利用欧洲中期天气预报中心（ECMWF）的再分析数据和等高线平流技术研究了对流层上层和平流层下层的水汽分布。水蒸气是主要的温室气体，了解决定其分布和运输的过程至关重要。特别令人感兴趣的是穿过对流层顶的水蒸气交换。本研究考虑了亚洲夏季风如何影响对流层上层和平流层下层的水分收支。亚洲夏季风区域被认为是深层热带以外对流层上层的重要水汽来源。季风对流湿润了位于动力对流层顶附近的高层季风反气旋区域，在那里等熵线从对流层进入平流层。等熵分析表明，该地区从对流层向平流层的输送通常被对流层顶周围的强位涡梯度所阻止。然而，中纬度天气扰动偶尔会与季风反气旋相互作用，并从其北侧拉出对流层空气细丝。这些细丝具有高湿度和低位涡度的特征，可以向北延伸，并将水汽不可逆地输送到北半球平流层下层。MOZAIC（空中客车在役飞机臭氧测量）数据被用作独立数据源来验证ECMWF分析得出的结果。
This study employs European Centre for Medium‐Range Weather Forecasts (ECMWF) re‐analysis data and the contour advection technique to investigate the water vapour distribution in the upper troposphere and lower stratosphere. Water vapour is the primary greenhouse gas and understanding the processes which determine its distribution and transport is crucial. Of special interest is the exchange of water vapour across the tropopause. This study considers how the Asian summer monsoon affects the moisture budget of the upper troposphere and lower stratosphere. The region of the Asian summer monsoon is identified as a significant moisture source for the upper troposphere outside the deep tropics. Monsoon convection moistens the region of the upper‐level monsoon anticyclone which is located close to the dynamical tropopause, where isentropes cross from the troposphere into the stratosphere. An isentropic analysis reveals that transport from the troposphere into the stratosphere in this region is normally prevented by the strong potential‐vorticity gradients around the tropopause. However, midlatitude synoptic disturbances occasionally interact with the monsoon anticyclone and pull filaments of tropospheric air from its northern flank. These filaments, characterized by high values of humidity and low values of potential vorticity, can extend far north and transport moisture irreversibly into the northern hemisphere lower stratosphere. MOZAIC (Measurement of OZone by Airbus In‐service airCraft) data are used as an independent data source to validate the results obtained from the ECMWF analyses.