Interannual Variability of the North American Cold Air Stream and Associated Synoptic Circulations
Interannual Variability of the North American Cold Air Stream and Associated Synoptic Circulations
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DOI：
10.1175/jcli-d-17-0104.1
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发表时间：
2017-11
影响因子：
4.9
通讯作者：
Y. Kanno;J. Walsh;T. Iwasaki
中科院分区：
文献类型：
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作者：
Y. Kanno;J. Walsh;T. Iwasaki
北半球冬季，位温低于280K的冷空气(CAM)通量在东亚和北美形成气候平均的CAM流。本文通过分析格陵兰岛和落基山脉之间60°N的CAM通量来诊断NA流的年际变化。第一个经验正交函数(EOF)表示NA流强度的变化。当第一主成分(PC1)为高正时，NA流的中心部分加强，落基山脉以东出现冷异常。同时，平流层极涡倾向于分裂或向NA移动。PC1与热带北半球模式高度相关，这意味着这种模式与NA流的强度有关。第二张EOF显示了北冰洋流向格陵兰岛或落基山脉的纵向移动。高度负的PC2导致从加拿大西部到美国中西部的冷异常。
AbstractIn boreal winter, the cold air mass (CAM) flux of air with a potential temperature below 280 K forms climatological mean CAM streams in East Asia and North America (NA). This study diagnoses the interannual variability of the NA stream by an analysis of the CAM flux across 60°N between Greenland and the Rocky Mountains. The first Empirical Orthogonal Function (EOF) represents the variations in intensity of the NA stream. When the first principal component (PC1) is highly positive, the central part of the NA stream is intensified, with cold anomalies east of the Rocky Mountains. At the same time, a stratospheric polar vortex tends to split or displace towards NA. PC1 is highly correlated with the Tropical Northern Hemisphere pattern, implying that this pattern is associated with the intensity of the NA stream. The second EOF shows a longitudinal shift of the NA stream toward Greenland or the Rocky Mountains. A highly negative PC2 results in a cold anomaly from western Canada to the Midwestern Unite...