南京信息工程大学孙博团队报道了欧亚大陆秋冬季降雪频率的显著年际变化和物理机制。这一研究成果于近日发表在《大气科学进展》上。

本文调查了欧亚大陆秋冬季降雪频率年际变化的主要模态，并探讨了其潜在的物理机制。

研究显示，秋季降雪频率的第一EOF模态(EOF1)为，在中西伯利亚高原(CSP)和欧洲主要表现为正异常，在中亚(CA)则相反。冬季EOF1表现为西伯利亚正异常，欧洲和东亚(EA)负异常。在秋季，EOF1与卡拉—拉普捷夫海(KLS)的海冰异常和北大西洋海表温度(SST)有关。

KLS海冰的增加可能会引起经向气温梯度和天气尺度波活动的增加，从而导致欧洲和CSP的降雪频率增加。KLS海冰异常和北大西洋SST异常的增加，既刺激了Rossby波向下游传播，又诱发了与降雪频率减少相对应的CA高异常。

相反，EOF1主要受冬季异常大气环流的影响。在北大西洋涛动(NAO)正相位，西伯利亚(欧洲)上空出现异常的深冷低压(暖高压)，从而导致西伯利亚的降雪频率增加(减少)。正NAO激发的天气尺度波活动可诱导Rossby波向下游传播，并在EA上空形成异常的上升和下降运动，从而抑制降雪。冬季的NAO可能受到印度洋偶极子和秋季巴伦支—卡拉—拉普捷夫海海冰的调制。

附：英文原文

Title: Distinct interannual variability and physical mechanisms of snowfall frequency over the Eurasian continent during autumn and winter

Author: Siyu Zhou, Bo Sun, Huijun Wang, Yi Zheng, Jiarui Cai, Huixin Li, Botao Zhou

Issue&Volume:

Abstract: This study investigated the dominant modes of interannual variability of snowfall frequency over the Eurasian continent during autumn and winter, and explored the underlying physical mechanisms. The first EOF mode (EOF1) of snowfall frequency during autumn is mainly characterized by positive anomalies over Central Siberian plateau (CSP) and Europe, and the opposite over Central Asia (CA). EOF1 during winter is characterized by positive anomalies in Siberia and negative anomalies in Europe and East Asia (EA). During autumn, EOF1 is associated with the anomalous sea ice in the Kara–Laptev seas (KLS) and sea surface temperature (SST) over the North Atlantic. Increased sea ice in the KLS may cause increased meridional air temperature gradient resulting in increased synoptic–scale wave activity, thereby inducing increased snowfall frequency over Europe and CSP. Anomalous increased sea ice in the KLS and SST in North Atlantic may both stimulate downstream propagation of Rossby waves and induce anomalous high in CA corresponding to decreased snowfall frequency. In contrast, EOF1 is mainly affected by the anomalous atmospheric circulation during winter. In the positive phase of the North Atlantic Oscillation (NAO), anomalous deep cold low (warm high) occurs over Siberia (Europe), and hence increased (decreased) snowfall frequency over Siberia (Europe). The synoptic-scale wave activity excited by the positive NAO can induce Rossby wave propagating downstream and contribute to anomalous high and descending motion over EA, which may inhibit snowfall. The NAO in winter may be modulated by the Indian Ocean dipole and sea ice in Barents-Kara-Laptev Seas in autumn.

DOI: 10.1007/s00376-024-3327-3

Source: http://www.iapjournals.ac.cn/aas/en/article/doi/10.1007/s00376-024-3327-3viewType=HTML