The tropical and extratropical-origin summer meridional teleconnections over East Asia
The tropical and extratropical-origin summer meridional teleconnections over East Asia
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东亚热带和温带夏季经向遥相关
DOI：
10.1007/s00382-018-04610-2
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发表时间：
2019-01
期刊：
影响因子：
4.6
通讯作者：
Yang Xiu Qun
中科院分区：
文献类型：
--
作者：
Sun Xuguang;Xu Yiming;Zhang Zhiqi;Yang Xiu Qun
东亚上空纬向遥相关是东亚夏季风的主要特征之一，也是热带和热带外中高纬影响东亚夏季风的重要途径。利用1979-2016年GPCP降水资料和NCEP/NCAR再分析资料，对东亚夏季降水和纬向风异常的纬压剖面进行了多变量反演，揭示了东亚夏季EA-MT的时空结构。根据其特征和主要来源，将夏季东亚-MT的两个主导模态分别命名为“EA-TMT”和“EA-XTMT”。这两种异常都表现出较强的年际变化，并在中高纬度地区表现出西风异常随高度向北倾斜的准正压结构，相应地，显著的降水异常被限制在长江流域纬向风异常的正下方，从而有助于夏季东亚-MT的建立和维持。东亚-TMT是由北太平洋西部的异常对流活动触发并在对流层中低层向北传播的，它与东亚夏季西风急流（EASWJ）强度和YRV降水异常有密切的关系，在代表热带起源的东亚-TMT方面比东亚/太平洋和太平洋-日本遥相关型优越上级。东亚-XTMT主要发生在喀拉海东南部，在整个对流层向东南方向传播，以北亚偶极子模态为主，主要与东亚西风带位置异常有关，有利于我国东部降水异常的“南涝北旱”格局。EA-TMT与夏季热带太平洋-印度洋海温异常密切相关，并与ENSO有一定的相关性，而EA-XTMT可能与春季北极西部和巴伦支海海冰密集度异常有关。此外，EA-TMT和EA-XTMT的联合贡献对于东亚夏季风的主要变化是必不可少的，其中EA-TMT起主要作用。
The meridional teleconnection over East Asia (EA-MT) is one of the major features of East Asian summer monsoon (EASM), and it is also the important pathway for the impacts from both tropical and extratropical middle-high latitudes on the EASM. To reveal the temporal-spatial structure of summer EA-MT, multivariate EOF is applied to the latitude-pressure cross section of combined summer precipitation and zonal wind anomalies over East Asia, using GPCP precipitation and NCEP/NCAR reanalysis dataset during the period 1979–2016. Two leading modes of summer EA-MT are obtained and identified as the tropical and extratropical-origin EA-MT in terms of their specific characteristics and major sources, named “EA-TMT” and “EA-XTMT”, respectively. Both of them show strong interannual variabilities, and they demonstrate a quasi-barotropic structure of westerly wind anomalies that slightly tilts northward with height in the mid-high latitudes, and accordingly significant precipitation anomalies are constrained right underneath the anomalous zonal wind around the Yangtze River valley (YRV), which in turn helps to establish and maintain the summer EA-MT. The EA-TMT is triggered by anomalous convective activities in the western North Pacific and propagates northward in the mid-low troposphere, it has close relationship with the anomalies of East Asian summer westerly jet (EASWJ) intensity and the YRV precipitation, which is superior over the East Asia/Pacific and Pacific-Japan teleconnection patterns in representing the tropical-origin EA-MT. The EA-XTMT is however mainly initiated in the southeast of Kara Sea and propagating southeastward in the whole troposphere, it is dominated by the North Asian dipole mode and mainly related to the EASWJ position anomaly, favoring a “South Flood North Drought” pattern of precipitation anomalies over East China. Meanwhile, the EA-TMT is closely related to the summer SST anomalies in the tropical Pacific-Indian ocean and partly correlated with ENSO, whereas the EA-XTMT is possibly linked to the spring sea ice concentration anomalies in the western Arctic and Barents Sea. Furthermore, the joint contributions of EA-TMT and EA-XTMT are essential for the major variability of EASM, wherein the EA-TMT plays a primary role.
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影响因子：
3.1
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