Increased Arctic influence on the midlatitude flow during Scandinavian Blocking episodes
Increased Arctic influence on the midlatitude flow during Scandinavian Blocking episodes
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斯堪的纳维亚阻塞期间北极对中纬度气流的影响增加
DOI：
10.1002/qj.3673
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
T. Jung
中科院分区：
文献类型：
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作者：
J. Day;I. Sandu;L. Magnusson;M. Rodwell;H. Lawrence;N. Bormann;T. Jung
最近的研究表明，北极遥相关在与中期天气预报相关的时间尺度上影响中纬度地区的天气。在这项研究中，我们使用了几种数值实验方法与最先进的全球业务数值天气预报系统，以进一步研究这一想法。聚焦于北方冬季，我们调查北极对中纬度天气的影响，以及当前北极观测系统对中纬度中期天气预报技能的影响是否在某些流态中更为明显。使用所谓的观测系统实验，我们证明，从数据同化系统中删除现场或卫星观测，用于创建预报的初始条件，恶化了中纬度天气预报技能的中期，特别是在北方亚洲。这种恶化在斯堪的纳维亚阻塞事件期间是最大的，在此期间：（a）由于该地区斜压性的增加，欧洲北极地区的误差增长增强，（B）高振幅行星波允许误差从北极传播到中纬度地区。斯堪的纳维亚阻塞在调节北极对中纬度地区的影响方面所发挥的重要作用，也在松弛实验中得到证实，并通过ERA5再分析和再预报的诊断分析。
Recent studies have suggested that Arctic teleconnections affect the weather of the midlatitudes on time‐scales relevant for medium‐range weather forecasting. In this study, we use several numerical experimentation approaches with a state‐of‐the‐art global operational numerical weather prediction system to investigate this idea further. Focusing on boreal winter, we investigate whether the influence of the Arctic on midlatitude weather, and the impact of the current Arctic observing system on the skill of medium‐range weather forecasts in the midlatitudes is more pronounced in certain flow regimes. Using so‐called Observing System Experiments, we demonstrate that removing in situ or satellite observations from the data assimilation system, used to create the initial conditions for the forecasts, deteriorates midlatitude synoptic forecast skill in the medium‐range, particularly over northern Asia. This deterioration is largest during Scandinavian Blocking episodes, during which: (a) error growth is enhanced in the European‐Arctic, as a result of increased baroclinicity in the region, and (b) high‐amplitude planetary waves allow errors to propagate from the Arctic into midlatitudes. The important role played by Scandinavian Blocking, in modulating the influence of the Arctic on midlatitudes, is also corroborated in relaxation experiments, and through a diagnostic analysis of the ERA5 reanalysis and reforecasts.