On the extratropical influence of variations of the upper tropospheric equatorial zonal mean zonal wind during boreal winter.

Gollan, Gereon and Greatbatch, Richard John (2015) On the extratropical influence of variations of the upper tropospheric equatorial zonal mean zonal wind during boreal winter. Open Access Journal of Climate, 28 (1). pp. 168-185. DOI 10.1175/JCLI-D-14-00185.1.

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Variations in the global tropospheric zonal mean zonal wind ([U]) during boreal winter are investigated using Rotated Empirical Orthogonal Functions applied to monthly means. The first two modes correspond to the Northern and Southern Annular Mode and modes 3 and 4 represent variability in the tropics. One is related to El Niño Southern Oscillation and the other has variability that is highly correlated with the time series of [U] at 150 hPa between 5°N and 5°S ([U150]E) and is related to activity of the Madden-Julian Oscillation. The extratropical response to [U150]E is investigated using linear regressions of 500 hPa geopotential height onto the [U150]E time series. We make use of reanalysis data and of the ensemble mean output from a relaxation experiment using the European Center for Medium Range Weather Forecasts model in which the tropical atmosphere is relaxed towards reanalysis data. The regression analysis reveals that a shift of the Aleutian low and a wave train across the North Atlantic are associated with [U150]E. We find that the subtropical waveguides and the link between the North Pacific and North Atlantic are stronger during the easterly phase of [U150]E. The wave train over the North Atlantic is associated with Rossby wave sources over the subtropical North Pacific and North America. Finally, we show that a linear combination of both [U150]E and the Quasi Biennial Oscillation in the lower stratosphere can explain the circulation anomalies of the anomalously cold European winter of 1962/63 when both were in an extreme easterly phase.

Document Type: Article
Additional Information: WOS:000347061200010
Keywords: Madden-Julian oscillation, Quasibiennial oscillation, Rossby waves, Stationary waves, Teleconnections, Seasonal forecasting; ISOLAA, SPP 1158 Antarktisforschung
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1175/JCLI-D-14-00185.1
ISSN: 0894-8755
Projects: ISOLAA, SPP Antarktisforschung, ISOLAA, SPP 1158 Antarktisforschung
Date Deposited: 03 Dec 2014 09:30
Last Modified: 01 Jan 2018 00:38
URI: http://oceanrep.geomar.de/id/eprint/26112

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