The modulation of Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation on winter Eurasian cold anomaly via the Ural blocking change
The modulation of Interdecadal Pacific Oscillation and Atlantic Multidecadal Oscillation on winter Eurasian cold anomaly via the Ural blocking change
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DOI：
10.1007/s00382-021-06119-7
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发表时间：
2021-05
期刊：
影响因子：
4.6
通讯作者：
B. Luo;D. Luo;A. Dai;I. Simmonds;Lixin Wu
中科院分区：
文献类型：
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作者：
B. Luo;D. Luo;A. Dai;I. Simmonds;Lixin Wu
观测结果表明，1965-1976年冬季欧亚寒冷异常（ECA）以欧亚大陆中部（40°-60°N, 60°-120°E）为中心，与2002-2013年相比，其向西南方向扩展的幅度更大。本文利用再分析资料分析乌拉尔阻塞（UB）与年代际太平洋涛动（IPO）和大西洋多年代际涛动（AMO）的关联，以解释1965-1976年和2002-2013年ECA的年代际变化。研究发现，1965-1976年冬季ECA与IPO负期（IPO−）和AMO负期（AMO−）相关，而2002-2013年冬季ECA与IPO−同时发生的AMO正期（AMO+）相关。与北大西洋正涛动有关的UB在IPO+和AMO−期间都相对短暂且快速逆行，但在IPO−和AMO+期间存在较长时间且表现出不同的纵向运动和位置。在IPO−期间，北大西洋中高纬度和欧亚高纬度地区受弱西风和较小的经向位涡梯度（PVy）影响，UB增长迅速，衰减缓慢，衰减阶段向西移动缓慢，导致欧亚大陆中部及其上游地区（30°-50°N, 30°-70°E）出现强烈的冷异常。由于逆行UB的缓慢衰变，AMO−具有类似的效果。而在AMO+UB期间，由于北大西洋（欧亚大陆）高纬度地区强（弱）西风和大（小）pvv的影响，UB增长缓慢，衰减迅速，呈现东移趋势，导致欧亚大陆中部及其下游地区出现强烈的冷异常。通过这些ub引起的次季节变化，年代际IPO−、AMO−和AMO+有助于解释1965-1976年和2002-2013年冬季平均ECA的年代际变化。
Observations reveal distinct interdecadal winter Eurasian cold anomaly (ECA) centered over central Eurasia (40°–60° N, 60°–120° E), with a more southwestward extension during 1965–1976 than during 2002–2013. In this paper, Ural blockings (UB) in association with the Interdecadal Pacific Oscillation (IPO) and Atlantic Multi-decadal Oscillation (AMO) are analyzed to explain the ECA’s decadal change from 1965–1976 to 2002–2013 using reanalysis data. It is found that the 1965–1976 winter ECA is associated with a negative-phase IPO (IPO−) together with negative-phase AMO (AMO−), while the 2002–2013 ECA is related to positive-phase AMO (AMO+) concurring with IPO−. UB mainly related to positive North Atlantic Oscillation is relatively short-lived and rapidly retrograde during both IPO+and AMO−, but long-lived and shows different longitudinal movements and positions during IPO−and AMO+. During IPO−, UB grows rapidly and decays slowly due to weak westerly winds and small meridional potential vorticity gradient (PVy) over North Atlantic mid-high latitudes and Eurasian high latitudes, and moves slowly westward during its decay stage, causing strong cold anomalies over central Eurasia and its upstream region (30°–50° N, 30°–70° E). AMO−has a similar effect due to the slow decay of retrograde UB. However, during AMO+UB grows slowly, decays rapidly and shows eastward movement due to strong (weak) westerly winds and large (small) PVyover North Atlantic (Eurasian) high latitudes, causing strong cold anomalies over central Eurasia and its downstream side. Through these UB-induced sub-seasonal changes, the interdecadal IPO−, AMO−and AMO+help explain the decadal variation of the winter-mean ECA from 1965–1976 to 2002–2013.