The Anomalous Merging of the African and North Atlantic Jet Streams during the Northern Hemisphere Winter of 2010

Harnik, N.; Galanti, E.; Martius, Olivia; Adam, O. (2014). The Anomalous Merging of the African and North Atlantic Jet Streams during the Northern Hemisphere Winter of 2010. Journal of Climate, 27(19), pp. 7319-7334. American Meteorological Society 10.1175/JCLI-D-13-00531.1

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The North Atlantic jet stream during winter 2010 was unusually zonal, so the typically separated Atlantic and African jets were merged into one zonal jet. Moreover, the latitude–height structure and temporal variability of the North Atlantic jet during this winter were more characteristic of the North Pacific. This work examines the possibility of a flow regime change from an eddy-driven to a mixed eddy–thermally driven jet. A monthly jet zonality index is defined, which shows that a persistent merged jet state has occurred in the past, both at the end of the 1960s and during a few sporadic months. The anomalously zonal jet is found to be associated with anomalous tropical Pacific diabatic heating and eddy anomalies similar to those found during a negative North Atlantic Oscillation (NAO) state. A Lagrangian back-trajectory diagnosis of eight winters suggests the tropical Pacific is a source of momentum to the Atlantic and African jets and that this source was stronger during the winter of 2010. The results suggest that the combination of weak eddy variance and fluxes in the North Atlantic, along with strong tropical heating, act to push the jet toward a merged eddy–thermally driven state. The authors also find significant SST anomalies in the North Atlantic, which reinforce the anomalous zonal winds, particularly in the eastern Atlantic.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Institute of Geography
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)

UniBE Contributor:

Romppainen-Martius, Olivia


500 Science > 550 Earth sciences & geology
900 History > 910 Geography & travel




American Meteorological Society




Monika Wälti-Stampfli

Date Deposited:

06 Oct 2014 15:47

Last Modified:

05 Dec 2022 14:37

Publisher DOI:





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