Wave‐breaking characteristics of midlatitude blocking
Wave‐breaking characteristics of midlatitude blocking
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DOI：
10.1002/qj.990
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发表时间：
2012-07
影响因子：
8.9
通讯作者：
G. Masato;B. Hoskins;T. Woollings
中科院分区：
文献类型：
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作者：
G. Masato;B. Hoskins;T. Woollings
本文从北半球冬季中纬度阻塞的破波特征入手，分析了北半球冬季中纬度阻塞的特征。Rossby波破裂被认为是阻塞发生的关键过程，因为它提供了阻塞典型的经向反转模式的机制。设计了两个指数来检测波浪破碎的主要特征，即方向(气旋/反气旋-破碎方向或DB指数)和气团的相对贡献(暖/冷-相对强度或RI指数)。DB指数的使用区分了欧亚地区的反气旋事件和洋盆上的气旋事件。在显示气旋型的三个区域中，一个在大西洋上空，另外两个在太平洋上空。第一个位于太平洋西侧，以暖空气挤压为主，第二个位于急流出口区的北部，那里的经向θ梯度要弱得多。用RI指数检测到了两种欧洲阻塞类型，该指数区分了以暖气团和冷气团为主的病例。后一种情况尤其显示出一个结构良好的偶极子，并伴随着温度和降水的强烈异常。版权所有(C)2011皇家气象学会
In this article, Northern Hemisphere winter midlatitude blocking is analysed through its wave‐breaking characteristics. Rossby wave breaking is identified as a key process in blocking occurrence, as it provides the mechanism for the meridional reversal pattern typical of blocking. Two indices are designed to detect the major properties of wave breaking, i.e. the orientation (cyclonic/anticyclonic–direction of breaking or DB index) and the relative contribution of air masses (warm/cold–relative intensity or RI index). The use of the DB index differentiates between the anticyclonic cases over Europe and Asia and the cyclonic events over the oceanic basins. One of the three regions displaying cyclonic type was found over the Atlantic Ocean, the other two being over the Pacific Ocean. The first of these is located over the western side of the Pacific and is dominated by warm air extrusions, whereas the second is placed northward of the exit region of the jet stream, where the meridional θ gradient is much weaker. Two European blocking types have been detected using the RI index, which separates out the cases dominated by warm and cold air masses. The latter cases in particular exhibited a well‐structured dipole, with associated strong anomalies in both temperature and precipitation. Copyright © 2011 Royal Meteorological Society