Combined Impacts of PDO and Two Types of La Nina on Climate Anomalies in Europe
Combined Impacts of PDO and Two Types of La Nina on Climate Anomalies in Europe
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PDO和两类拉尼娜现象对欧洲气候异常的综合影响
DOI：
10.1175/jcli-d-16-0376.1
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发表时间：
2017-05-01
影响因子：
4.9
通讯作者：
Graf, Hans-F.
中科院分区：
文献类型：
--
作者：
Ding, Shuoyi;Chen, Wen;Graf, Hans-F.
研究了太平洋年代际振荡（PDO）和两类拉尼娜现象对欧洲气候异常的联合影响。特别是，负PDO相位和两种不同类型的拉尼娜事件的组合有利于强而显着的北大西洋涛动（NAO）模式异常与相反的极性。对于中太平洋拉尼娜事件，可以检测到明显的正NAO信号，并伴随着正的地面气温异常和欧洲降水异常的偶极结构。此外，还形成了一个典型的负太平洋-北美（PNA）遥相关型，其中包括美国东南部的高压异常，这可能通过加强斜压性和局地涡动-平均流相互作用而有助于NAO异常的发展和维持。然而，对于东太平洋拉尼娜，在高纬地区可以观察到一个纬向波列，这与典型的PNA结构有很大的不同。在这里，一个异常的反气旋在格陵兰岛南部支持一个负NAO模式，通过当地涡平均流相互作用和相关的涡度平流。因此，反SAT和降水异常发生在欧洲。进一步的分析表明，北太平洋波列和天气涡与平均流的相互作用对NAO异常位相的形成起着重要作用。CP型和EP型拉尼娜事件的波列不同，可能是由于不同类型的海温异常以及相应的对流层上层背景西风异常所引起的异常对流的位置和强度不同所致。
Combined impacts of the Pacific decadal oscillation (PDO) and two types of La Nina on climate anomalies in Europe are studied. Particularly, the conjunction of the negative PDO phase and two different types of La Nina events favors strong and significant North Atlantic Oscillation (NAO) pattern anomalies with opposite polarity. For the central Pacific (CP) La Nina, a clear positive NAO signal can be detected, which is accompanied by positive surface air temperature (SAT) anomaly and a dipolar structure of precipitation anomalies in Europe. In addition, a typical negative Pacific-North America (PNA) teleconnection pattern forms, including a high pressure anomaly over the southeastern United States, which may contribute to the development and maintenance of the NAO anomaly by strengthening the baroclinicity and the local eddy-mean flow interaction. However, for the eastern Pacific (EP) La Nina, a zonal wave train in the high latitudes can be observed, which is quite different from the typical PNA structure. Here, an anomalous anticyclone over southern Greenland supports a negative NAO pattern through the local eddy-mean flow interaction and the associated vorticity advection. Hence, reversed SAT and precipitation anomalies occur over Europe. Further analyses indicate that the wave trains emanating from the North Pacific and the synoptic eddy-mean flow interaction play essential roles in forming the anomalous NAO phases. The different wave trains for the CP and EP La Nina events may be attributed to the differences in the location and intensity of anomalous convection induced by different types of SST anomaly as well as by the corresponding background westerly wind anomalies in the upper troposphere.