The weakening summer circulation in the Northern Hemisphere mid-latitudes
The weakening summer circulation in the Northern Hemisphere mid-latitudes
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DOI：
10.1126/science.1261768
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发表时间：
2015-04-17
期刊：
影响因子：
56.9
通讯作者：
Beckmann, Johanna
中科院分区：
文献类型：
--
作者：
Coumou, Dim;Lehmann, Jascha;Beckmann, Johanna
北极的快速变暖可能会通过减少向极地的温度梯度来影响中纬度环流。最大的变化通常预计在秋季或冬季，但是否发生了重大变化仍有争议。在这里，我们报告显着减弱的夏季环流检测三个关键的动力学量：（i）纬向平均纬向风，（ii）涡动动能（EKE），（iii）快速移动的Rossby波的振幅。纬向风减弱的原因是向极方向温度梯度减小。Rossby波和EKE的变化与气候模式预测的回归分析和季节周期的变化是一致的。每月的极端高温与低EKE有关，因此观察到的减弱可能导致最近夏季更持久的热浪。
Rapid warming in the Arctic could influence mid-latitude circulation by reducing the poleward temperature gradient. The largest changes are generally expected in autumn or winter, but whether significant changes have occurred is debated. Here we report significant weakening of summer circulation detected in three key dynamical quantities: (i) the zonal-mean zonal wind, (ii) the eddy kinetic energy (EKE), and (iii) the amplitude of fast-moving Rossby waves. Weakening of the zonal wind is explained by a reduction in the poleward temperature gradient. Changes in Rossby waves and EKE are consistent with regression analyses of climate model projections and changes over the seasonal cycle. Monthly heat extremes are associated with low EKE, and thus the observed weakening might have contributed to more persistent heat waves in recent summers.