Persistent anomalies of the extratropical Northern Hemisphere wintertime circulation as an initiator of El Niño/Southern Oscillation events

Journal Article · 31 August 2017 · Scientific Reports

DOI: https://doi.org/10.1038/s41598-017-09580-9 · OSTI ID:1430238

Anderson, Bruce T.  ^[1]; Hassanzadeh, Pedram  ^[2]; Caballero, Rodrigo  ^[3]

---

1. Boston Univ., MA (United States). Dept. of Earth and Environment
2. Rice Univ., Houston, TX (United States). Dept. of Mechanical Engineering and Earth Science
3. Stockholm Univ. (Sweden). Dept. of Meteorology and Bolin Center for Climate Research

Climates 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 in this paper 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.

• Research Organization: Boston Univ., MA (United States)
• Sponsoring Organization: USDOE; National Science Foundation (NSF); Swedish Research Council (SRC)
• Grant/Contract Number: SC0004975
• OSTI ID: 1430238
• Journal Information: Scientific Reports, Vol. 7, Issue 1; ISSN 2045-2322
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United States
• Language: English