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Browsing Mechanical Engineering Publications by Author "Anderson, Bruce T."
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Item Persistent anomalies of the extratropical Northern Hemisphere wintertime circulation as an initiator of El Niño/Southern Oscillation events(Springer Nature, 2017) Anderson, Bruce T.; Hassanzadeh, Pedram; Caballero, RodrigoClimates across both hemispheres are strongly influenced by tropical Pacific variability associated with the El Niño/Southern Oscillation (ENSO). Conversely, extratropical variability also can affect the tropics. In particular, seasonal-mean alterations of near-surface winds associated with the North Pacific Oscillation (NPO) serve as a significant extratropical forcing agent of ENSO. However, it is still unclear what dynamical processes give rise to year-to-year shifts in these long-lived NPO anomalies. Here we show that intraseasonal variability in boreal winter pressure patterns over the Central North Pacific (CNP) imparts a significant signature upon the seasonal-mean circulations characteristic of the NPO. Further we show that the seasonal-mean signature results in part from year-to-year variations in persistent, quasi-stationary low-pressure intrusions into the subtropics of the CNP, accompanied by the establishment of persistent, quasi-stationary high-pressure anomalies over high latitudes of the CNP. Overall, we find that the frequency of these persistent extratropical anomalies (PEAs) during a given winter serves as a key modulator of intraseasonal variability in extratropical North Pacific circulations and, through their influence on the seasonal-mean circulations in and around the southern lobe of the NPO, the state of the equatorial Pacific 9–12 months later.