Southward cold airmass flux associated with the East Asian winter monsoon: Diversity and impacts
Southward cold airmass flux associated with the East Asian winter monsoon: Diversity and impacts
复制标题
与东亚冬季风相关的南向冷气团通量：多样性和影响
DOI：
10.1175/jcli-d-20-0319.1
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发表时间：
2021-01
影响因子：
4.9
通讯作者：
Toshiki Iwasaki
中科院分区：
文献类型：
--
作者：
Liu Qian;Chen Guixing;Wang Lin;Yuki Kanno;Toshiki Iwasaki
冬季季风通过跨越纬度的南下冷气团通量对东亚产生强烈影响，称为冷空气爆发(CAO)。CAO在经向范围和诱发天气方面具有较高的差异性。利用1958-2016年逐日归一化的50°N和30°N冷气团通量资料，将CAO分为三类：高-中纬度事件(H-M)、高-低纬事件(H-L)和中低纬度事件(M-L)。在归一化强度方面，H-L型持续时间最长，M-L型更容易产生较强的CAO。H-L和H-M事件的特征是欧亚高纬冷气团通量的大尺度偶极子模式，前(后)事件的特征是西伯利亚上空的反气旋性环流(东北亚气旋性环流)较强。而L地震则以东北亚气旋性异常为特征，没有明显的高纬度前兆。近地面气团冷度异常以H-L事件最大，M-L事件以偏北风为主。因此，H-L事件在东亚引起了普遍的持续低温，而M-L事件则主要在低纬地区引起了急剧的降温。与MJO耦合的H-L和M-L事件均使中国南海降水增加，而H-M事件使中国南部降水增加。此外，自20世纪80年代以来，H-L和M-L事件的发生经历了一个长期的减少，这导致东亚极端寒冷地区的增温趋势比冬季中低纬平均气温的增温趋势更强。
The winter monsoon has strong impacts on East Asia via latitude-crossing southward cold airmass fluxes called cold air outbreaks (CAOs). CAOs have a high diversity in terms of meridional extent and induced weather. Using the daily cold airmass flux normalized at 50°N and 30°N during 1958–2016, we categorize the CAOs into three groups: high–middle (H–M), high–low (H–L) and middle–low (M–L) latitude events. The H–L type is found to have the longest duration, and the M–L type is prone to the strong CAOs regarding normalized intensity. The H–L and H–M events feature a large-scale dipole pattern of cold airmass flux over high-latitude Eurasia, and the former (latter) events feature relatively strong anticyclonic circulation over Siberia (cyclonic circulation over northeastern Asia). In contrast, the M–L events are characterized by a cyclonic anomaly over northeastern Asia but no obvious high-latitude precursor. The H–L events have the greatest coldness anomaly in airmasses near the surface, and the M–L events mainly feature a strong northerly wind. As a result, the H–L events induce widespread long-lasting low temperatures over East Asia, while the M–L events induce a sharp temperature drop at mainly low latitudes. Both H–L and M–L events coupling with the MJO enhance rainfall over the South China Sea, while H–M events increase rainfall over southern China. Moreover, the occurrences of H–L and M–L events experience a long-term decrease since the 1980s, which induce a stronger warming trend in the cold extremes than in the winter mean temperature at mid-low latitudes over East Asia.