A feature‐based metric of the waviness of the wintertime, Northern Hemisphere polar, and subtropical jets is developed and applied to three different reanalysis data sets. The analysis first identifies a “core isertel” along which the circulation per unit length is maximized in the separate polar (315:330K) and subtropical (340:355K) jet isentropic layers. Since the core isertel is, by design, an analytical proxy for the respective jet cores, the waviness of each jet is derived by calculating a hemispheric average of the meridional displacements of the core isertel from its equivalent latitude—the southern extent of a polar cap whose area is equal to the area enclosed by the core isertel. Analysis of the seasonal average waviness over the time series of the various data sets reveals that both jets have become systematically wavier while exhibiting no trends in their average speeds. The waviness of each jet evolves fairly independently of the other in most cold seasons and the slow northward creep of the polar jet is statistically significant. Finally, comparison of the composites of the waviest and least wavy seasons for each species reveals that such interannual variability is manifest in familiar large‐scale circulation anomalies.

中文翻译：

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北半球冬季极地和亚热带喷气波度的最新趋势

开发了一种基于特征的冬季起伏，北半球极地和亚热带急流的度量，并将其应用于三个不同的再分析数据集。该分析首先确定一个“核心isteltel”，在单独的极性（315：330K）和亚热带（340：355K）射流等熵层中，每单位长度的循环量最大。由于核心isertel在设计上是各个射流核心的分析替代品，因此通过从等效纬度（即极地盖的南部范围）计算核心isertel的子午线位移的半球平均值，可以得出每个射流的波纹度其面积等于核心isertel包围的面积。对各种数据集的时间序列上的季节性平均起伏度的分析表明，这两种喷气机已经系统地起伏，而它们的平均速度没有任何趋势。在大多数寒冷季节中，每架喷气机的波纹都与另一架喷气机相当独立地演变，并且极地喷气机向北缓慢的蠕变在统计上是显着的。最后，对每个物种的最短和最短波浪季节的合成进行比较后发现，这种年际变化在熟悉的大规模环流异常中很明显。