Understanding the contrasting North Atlantic Oscillation anomalies of the winters of 2010 and 2014

• Published in: Geophysical Research Letters
• Main Authors: Rivière, Gwendal, Drouard, Marie
• Other Authors: Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: storm track dynamics; North Atlantic Oscillation; Rossby wave breaking; Synoptic wave trains; Earth Science; [SDU]Sciences of the Universe [physics]; Pacific; North Atlantic; North Atlantic oscillation
• Online Access: https://hal.science/hal-04114761; https://hal.science/hal-04114761/document; https://hal.science/hal-04114761/file/Geophysical%20Research%20Letters%20-%202015%20-%20Rivi%20re%20-%20Understanding%20the%20contrasting%20North%20Atlantic%20Oscillation%20anomalies%20of%20the.pdf; https://doi.org/10.1002/2015GL065493

International audience The present study investigates the two contrasting winters of 2010 and 2014 during which the North Atlantic Oscillation (NAO) was mainly negative and positive, respectively. In the North Pacific, contrasting anomalies were also present, with a straight zonal Pacific jet in 2010 and a strong poleward deviation of the Pacific jet in its exit region in 2014. Using reanalysis data sets and adopting a nonlinear initial-value approach with a quasi-geostrophic model, we show that the Pacific-North American anomalies are responsible for shaping synoptic wave trains propagating across North America. This in turn largely determines the nature of wave breaking and the synoptic eddy feedback onto the mean flow in the North Atlantic and finally the NAO phase. In such a proposed mechanism, synoptic wave activity forms the cornerstone of the dynamical relationship between the North Pacific and North Atlantic large-scale anomalies during the contrasting winters of 2010 and 2014.