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The weakening summer circulation in the Northern Hemisphere mid-latitudes

  • Rapid warming in the Arctic could influence mid-latitude circulation by reducing the poleward temperature gradient. The largest changes are generally expected in autumn or winter, but whether significant changes have occurred is debated. Here we report significant weakening of summer circulation detected in three key dynamical quantities: (i) the zonal-mean zonal wind, (ii) the eddy kinetic energy (EKE), and (iii) the amplitude of fast-moving Rossby waves. Weakening of the zonal wind is explained by a reduction in the poleward temperature gradient. Changes in Rossby waves and EKE are consistent with regression analyses of climate model projections and changes over the seasonal cycle. Monthly heat extremes are associated with low EKE, and thus the observed weakening might have contributed to more persistent heat waves in recent summers.

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Author:Dim CoumouORCiDGND, Jascha Lehmann, Johanna Beckmann
ISSN:0036-8075 (print)
ISSN:1095-9203 (online)
Pubmed Id:http://www.ncbi.nlm.nih.gov/pubmed?term=25765067
Parent Title (English):Science
Publisher:American Assoc. for the Advancement of Science
Place of publication:Washington
Document Type:Article
Year of first Publication:2015
Year of Completion:2015
Release Date:2017/03/27
First Page:324
Last Page:327
Funder:German Research Foundation [CO994/2-1]; German Federal Ministry of Education and Research [01LN1304A]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie
Peer Review:Referiert