Characterizing ENSO Coupled Variability and Its Impact on North American Seasonal Precipitation and Temperature Journal of Climate

Two questions are addressed in this paper: whether ENSO can be adequately characterized by simple, seasonally invariant indices and whether the time series of a single component—SST or OLR—provides a sufficiently complete representation of ENSO for the purpose of quantifying U.S. climate impacts. Here, ENSO is defined as the leading mode of seasonally varying canonical correlation analysis (CCA) between anomalies of tropical Pacific SST and outgoing longwave radiation (OLR). The CCA reveals that the strongest regions of coupling are mostly invariant as a function of season and correspond to an OLR region located in the central Pacific Ocean (CP-OLR) and an SST region in the eastern Pacific that coincides with the Niño-3 region. In a linear context, the authors explore whether the use of a combined index of these SST and OLR regions explains additional variance of North American temperature and precipitation anomalies beyond that described by using a single index alone. Certain seasons and regions benefit from the use of a combined index. In particular, a combined index describes more variability in winter/spring precipitation and summer temperature. Grant no. NA12OAR4310082

本文旨在解答两个核心问题：其一，能否通过简单的季节不变指数充分表征厄尔尼诺-南方涛动（ENSO）；其二，针对量化美国气候影响的研究目标，仅采用海表温度（SST）或向外长波辐射（OLR）单一分量的时间序列，是否足以完整表征ENSO。
本文将ENSO定义为热带太平洋SST异常与向外长波辐射（OLR）异常之间的季节变化型典型相关分析（CCA）的第一主导模态。典型相关分析结果显示，耦合作用最强的区域基本不随季节变化，对应位于太平洋中部的OLR区域（CP-OLR）以及与尼诺3（Niño-3）区域重合的东太平洋SST区域。
在线性分析框架下，作者探究了相较于仅使用单一指数，采用上述SST与OLR区域的复合指数，能否额外解释北美气温与降水异常的更多方差。
部分季节与区域可从复合指数的应用中获益，具体而言，复合指数可更充分地刻画冬/春季降水与夏季气温的变异性。
资助编号：NA12OAR4310082