Long‐lived Rossby wave trains as precursors to strong winter cyclones over Europe
Long‐lived Rossby wave trains as precursors to strong winter cyclones over Europe
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DOI：
10.1002/qj.2191
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发表时间：
2014-04
影响因子：
8.9
通讯作者：
V. Wirth;J. Eichhorn
中科院分区：
文献类型：
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作者：
V. Wirth;J. Eichhorn
利用45年的再分析数据，对北半球冬季强地表气旋与长寿命对流层上层罗斯比波列之间的统计联系进行了检验。选取中欧地面气压异常低于产生最低值的5%的阈值的日期。这些日期对流层上层经向风的合成（包括时间上的领先或滞后）显示出波浪列的明显迹象。复合波列存在超过两周，向东传播超过360°经度。相比之下，个别低点和高点的相速度接近于零，复合表面低点也是如此。当波列在北美东海岸传播时，有一个明显的向北移动。虽然这种复合波列在统计上是高度显著的，但在平均值上有很大的分散。定义了一个指数，用于量化任意日期对流层上层经向风型与某一超前或滞后的复合波列的相似性。如果该指数的正值较大，则几天后中欧上空出现强地面气旋的可能性增大。与先前一项关注太平洋气旋的研究相比，显示出显著的差异。
The statistical connection between strong surface cyclones over Europe and long‐lived upper‐tropospheric Rossby wave trains is examined for the Northern Hemisphere winter season using 45 years of reanalysis data. Dates are selected for which the surface pressure anomaly over Central Europe is below a threshold yielding the 5% of lowest values. Composites of upper tropospheric meridional wind for these dates (including a lead or lag in time) display clear signs of a wave train. The composite wave train lives for over two weeks and propagates eastward over more than 360° longitude. The phase speed of individual lows and highs, by contrast, is close to zero and the same is true for the composite surface low. There is a pronounced northward shift of the wave train as it propagates over the North American East coast. Although this composite wave train is statistically highly significant, there is large scatter about the mean. An index is defined that quantifies the similarity of the upper‐tropospheric meridional wind pattern for an arbitrary date with the composite wave train for a certain lead or lag. Given large positive values of the index, there is an enhanced probability of a strong surface cyclone over Central Europe a few days later. Comparison with a previous study focusing on Pacific cyclones shows noteworthy differences.