Asymmetric Modulation of ENSO Teleconnections by the Interdecadal Pacific Oscillation
Asymmetric Modulation of ENSO Teleconnections by the Interdecadal Pacific Oscillation
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DOI：
10.1175/jcli-d-17-0663.1
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发表时间：
2018-09-01
影响因子：
4.9
通讯作者：
Timm, Oliver Elison
中科院分区：
文献类型：
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作者：
Dong, Bo;Dai, Aiguo;Timm, Oliver Elison
ENSO的远程影响随着年代际太平洋涛动（IPO）的不同阶段而变化。本文分析了1920年至2014年的观测和再分析数据，提出了IPO对ENSO遥相关调制的全球综合，然后进行了建模研究。回归的地面空气温度T，降水P，大气环流IPO和ENSO指数显示ENSO和IPO遥相关区域T和P的空间格局，幅度和季节性方面的实质性差异。IPO对ENSO遥相关的调制作用随IPO和ENSO位相的不同而不对称变化。对于一个给定的ENSO位相，IPO的调制在其两个位相之间是不对称的;对于一个给定的IPO SST异常，其影响取决于它是否叠加在厄尔尼诺、拉尼娜或中性ENSO上。IPO调制与大气对热带SST异常的响应有关，表现在低纬的Hadley环流和步行者环流以及热带外的Rossby波列，包括北方半球的太平洋-北美（PNA）型。一组数值试验进一步表明，非线性Clausius-Clapeyron关系引起的非对称调制，使得大气环流对同样的IPO引起的SST距平的响应在暖期大于冷期，且对暖期的响应大于冷期的响应。这种不对称性主要取决于热带太平洋平均状态和热带海温异常，其次是热带外海温异常。
Remote influences of ENSO are known to vary with different phases of the interdecadal Pacific oscillation (IPO). Here, observational and reanalysis data from 1920 to 2014 are analyzed to present a global synthesis of the IPO's modulation on ENSO teleconnections, followed by a modeling investigation. Regressions of surface air temperature T, precipitation P, and atmospheric circulations upon IPO and ENSO indices reveal substantial differences between ENSO and IPO teleconnections to regional T and P in terms of spatial pattern, magnitude, and seasonality. The IPO's modulation on ENSO teleconnections asymmetrically varies with both IPO and ENSO phases. For a given ENSO phase, IPO's modulations are not symmetric between its two phases; for a given IPO SST anomaly, its influence depends on whether it is superimposed on El Nino, La Nina, or neutral ENSO. The IPO modulations are linked to the atmospheric response to tropical SST anomalies, manifested in the local Hadley circulation and the local Walker circulation at low latitudes and the Rossby wave train in the extratropics, including the Pacific-North American (PNA) pattern in the Northern Hemisphere. A set of numerical experiments using CAM5 forced with different combinations of the IPO- and ENSO-related SSTs further shows that the asymmetric modulation arises from the nonlinear Clausius-Clapeyron relation, so that the atmospheric circulation response to the same IPO-induced SST departure is larger during a warm rather than a cold ENSO phase, and the response to a warm IPO state is larger than that to a cold IPO state. The asymmetry depends primarily on the tropical Pacific mean state and tropical SST anomalies and secondarily on extratropical SST anomalies.