Causes of the extreme snowfall anomaly over the northeast Tibetan plateau in early winter 2018
Causes of the extreme snowfall anomaly over the northeast Tibetan plateau in early winter 2018
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DOI：
10.1007/s00382-020-05556-0
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发表时间：
2021-01
期刊：
影响因子：
4.6
通讯作者：
Hongyan Shen;Junhu Zhao;K. Y. Cheung;Lijuan Chen;Xiaocheng Yu;Tingting Wen;Z. Gong;G. Feng
中科院分区：
文献类型：
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作者：
Hongyan Shen;Junhu Zhao;K. Y. Cheung;Lijuan Chen;Xiaocheng Yu;Tingting Wen;Z. Gong;G. Feng
2018年初冬（11 - 12月），青藏高原东北部出现了一次特大降雪过程，降雪量为1961年以来最大。有必要更好地了解这次极端降雪事件的原因并揭示其物理机制。本文分析了这次极端降雪过程的特征及其与大气环流异常和海表温度异常的可能联系。结果表明：2018年初冬，中纬度地区存在类似欧亚遥相关的环流型，西伯利亚高压周期性加强，有利于北方冷气流进入西北太平洋，为降雪提供了适宜的温度条件。(2)低纬向和中纬向水汽输送都明显大于正常，导致更多的水汽通过西部和南部边界进入NTP地区，导致自1961年以来第二高的净水汽输入，并为极端降雪创造了足够的连续水汽条件。(3)斜压性和大气环流的不稳定性，以及西北太平洋上空异常的冷暖平流和垂直运动，为这次降雪提供了动力条件。(4)在暖厄尔尼诺南方涛动（ENSO）事件和热带印度洋偶极子（IOD）海温正位相的背景下，IOD模态遥影响形成的EU型控制了横跨欧亚大陆的中纬度地区。欧亚地区EU遥相关的正异常分别引导了强水汽通过西部边界和南部边界进入NTP。此外，ENSO/IOD的影响导致北方印度洋和西北太平洋以反气旋为主，造成更多的水汽从热带地区向北输送。相应地，青藏高原东缘沿着有充足的水汽进入高原，为强降雪过程提供了水汽条件。
An extremely heavy snowfall event occurred in early winter (November–December) 2018 over the northeast of Tibetan Plateau (NTP), with snowfall amounts ranking the highest since 1961. It is necessary to better understand the causes and reveal the physical mechanism of this extreme snowfall event. In this article, the features of this extreme snowfall event and its possible linkage with atmospheric circulation anomalies, and sea surface temperature (SST) anomaly effects are analyzed. The results show that in early winter 2018, (1) there was a similar Eurasian teleconnection (EU) pattern in the mid-latitudes with a periodic strengthening of the Siberian High, which favored northern cold airflow into the NTP, providing the suitable temperature conditions for snowfall. (2) Low-latitude meridional and mid-latitude zonal water vapor transport were both significantly greater than normal, causing much more water vapor flow than normal into the NTP region through the western and southern boundaries, leading to the second highest net water vapor input since 1961 and creating sufficient continuous water vapor conditions for extreme snowfall. (3) The baroclinicity and the instability of the atmospheric circulation, accompanied by abnormal cold and warm advection and vertical movement over the NTP, provided the dynamic atmospheric conditions for the snowfall event. (4) Under the background of warm El Niño Southern Oscillation (ENSO) event and the positive phase of the Tropical Indian Ocean dipole (IOD) SST, the EU pattern initiated by the tele-influence of IOD mode dominated the midlatitude region across Eurasia continent. The positive anomalies of EU teleconnection over western Asia guided the heavy water vapor flow into the NTP through the western and southern boundaries, respectively. In addition, the effects of ENSO/IOD caused the northern Indian Ocean and northwest Pacific to be dominated by anticyclones, creating more northward water vapor transport from the tropical region. Accordingly, sufficient water vapor flowed into the NTP along the eastern edge of the Tibetan Plateau, providing the moisture conditions for the severe snowfall event.