In this study, spatial and temporal variations of spring compound dry and hot events (CDHEs) over northern Asia (NA) during 1950–2020 and the related possible mechanisms are investigated on the interannual timescale. The standardized compound event indicator (SCEI) is used to represent compound dry and hot conditions over NA, which is validated by the observed summer case of CDHEs over western Russia in 2010. The first empirical orthogonal function (EOF1) mode of the SCEI over NA presents a monopole pattern, while the EOF2 mode shows an east-west dipole pattern. Possible mechanism analysis indicates that the CDHEs tend to be modulated by local high-pressure anomalies, accompanied by reduced cloud cover and more solar radiation. The high-pressure anomalies can lead to warm temperature and water vapor divergence, which synergistically contributes to the occurrence of CDHEs. Further analysis shows that the EOF1 mode is jointly affected by the Scandinavian (SCAND) pattern and the Arctic Oscillation (AO); while the EOF2 mode is influenced by the Atlantic-Eurasian (AEA) teleconnection. Moreover, the North Atlantic tripolar pattern of sea surface temperature (SST) can influence the EOF1 mode through changing the AO. And the diagonal tripolar SST pattern over the North Atlantic affects the EOF2 mode via altering the AEA pattern. The influence of the SST patterns is further confirmed by numerical experiments using the Community Atmospheric Model version CAM-5.3.

中文翻译：

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北亚春季复合干热事件年际变率的主要模式及可能的机制


本研究在年际时间尺度上研究了 1950—2020 年北亚 （NA） 春季复合干热事件 （CDHEs） 的时空变化以及相关的可能机制。标准化复合事件指标 （SCEI） 用于表示 NA 上的复合干热条件，2010 年在俄罗斯西部观察到的 CDHE 夏季病例证实了这一点。NA 上 SCEI 的第一经验正交函数 （EOF1） 模式呈现单极子模式，而 EOF2 模式显示东西向偶极子模式。可能的机制分析表明，CDHE 往往受到局部高压异常的调节，伴随着云层覆盖的减少和太阳辐射的增加。高压异常可导致温暖的温度和水蒸气发散，从而协同促进 CDHE 的发生。进一步分析表明，EOF1 模式受斯堪的纳维亚 （SCAND） 模式和北极涛动 （AO） 共同影响;而 EOF2 模式受大西洋-欧亚 （AEA） 遥相关的影响。此外，北大西洋海面温度 （SST） 的三极型型可以通过改变 AO 来影响 EOF1 模式。北大西洋上空的对角线三极 SST 模式通过改变 AEA 模式来影响 EOF2 模式。使用社区大气模型 CAM-5.3 版的数值实验进一步证实了 SST 模式的影响。