冬季东北冷涡的时空变化特征

基于1967—2017年美国环境预报中心和国家大气研究中心(NCEP/NCAR)的逐日再分析资料及英国气象局哈德来中心(Hadley Centre)的海温资料,通过计算冬季东北冷涡结构的特征指数并利用经验正交函数分解等方法,研究了冬季东北冷涡的时空变化特征及其与环流和海温变化的联系。结果表明:(1)冬季东北冷涡具有显著的年际变化与年代际变化特征,各指数年际分量的方差贡献率较大;冷涡强度与经、纬度呈正相关,且经、纬度之间呈正相关;(2)年际尺度第一模态反映了冬季东北冷涡气候平均位置以南为正(负)异常而以北为负(正)异常的南北反位相变化特征,第二模态反映了冬季东北冷涡在气候平均位置附近强度一致增强(强弱)的变化特征,而年代际尺度主要反映在第一模态,即冬季东北冷涡在气候平均位置附近强度一致增强(强弱)的变化特征;(3)北大西洋涛动(North Atlantic Oscillation, NAO)和西大西洋遥相关型(Western Atlantic, WA)的位相转换可能与年代际尺度冬季东北冷涡的强度强弱变化有关。

Temporal and spatial variation characteristics of northeast cold vortex in winter

Based on the daily reanalysis data of NCEP/NCAR and the Sea Surface Temperature (SST) data of Met Office Hadley Centre from 1967 to 2017, the characteristic index of northeast cold vortex structure in winter was calculated and the EOF decomposition method was used to study the temporal and spatial variation characteristics of northeast cold vortex in winter as well as its relationship with circulation and SST. Results show that (1) in winter, the northeast cold vortex has a significant interannual and interdecadal variation, and the interannual components of each index have a greater contribution to the variance; the intensity of cold vortex is positively correlated with latitude and longitude, and positively correlated with latitude and longitude. (2) The EOF results show that the first mode of interannual scale reflects that the northeast cold vortex in winter has a pair of North-South reverse phase characteristics of the climatic mean position with the south as a positive (negative) anomaly and the north as a negative (positive) anomaly, while the overall negative (positive) anomaly area of the second mode reflects the change of the strength of the cold vortex intensity at the average climate position. The interdecadal scale is mainly reflected in the first mode, namely, the intensity of the cold vortex intensity changes in the average position of the climate reflected by the overall negative (positive) anomaly area. (3) Further correlation analysis shows that the phase transition of the North Atlantic Oscillation (NAO) and the Western Atlantic (WA) teleconnection is related to the strength of the northeast cold vortex in winter on the interdecadal scale.