Surface anticyclones connected to the ridge of an upper-tropospheric Rossby wave are the main dynamical drivers of mid-latitude summer heatwaves. It is, however, unclear to what extent an anomalously low zonal phase speed of the wave in the upper troposphere is necessary for persistent temperature extremes at the surface. Here, we use spectral decomposition to separate fast and slow synoptic-scale waves. A composite analysis of ERA5 reanalysis data reveals that, while in some regions heatwaves become more frequent during episodes of weak or no phase propagation, temperature extremes in other regions are commonly associated with more rapidly eastward propagating Rossby waves. Reflected in the mean heatwave duration as well, this relationship is possibly linked to a longitudinal phase preference of slow and fast waves or a meridional storm track shift. These findings open up new questions about the influence of mid-latitude dynamics on temperature extremes.

中文翻译：

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热浪位置变化与罗斯贝波相速度的关系


与对流层上层罗斯贝波脊相连的表面反气旋是中纬度夏季热浪的主要动力驱动因素。然而，目前尚不清楚对流层上层波的异常低纬向相速度在多大程度上对于地表持续极端温度是必要的。在这里，我们使用谱分解来分离快速和慢速的天气尺度波。 ERA5再分析数据的综合分析表明，虽然在某些地区热浪在弱相传播或无相传播期间变得更加频繁，但其他地区的极端温度通常与更快地向东传播的罗斯贝波有关。这种关系也反映在平均热浪持续时间上，可能与慢波和快波的纵向相位偏好或经向风暴路径移动有关。这些发现提出了有关中纬度动力学对极端温度影响的新问题。