Identification

Title

Impact of Ural blocking on winter warm Arctic-cold Eurasian anomalies. Part II: The link to the North Atlantic Oscillation

Abstract

In Part I of this study, the Ural blocking (UB)-induced amplification role of winter warm Arctic–cold Eurasian (WACE) anomalies has been examined. It was found that the long-lived UB together with the positive North Atlantic Oscillation (NAO+) significantly contributes to the amplification of the WACE pattern. The present study examines how the UB variability affects quasi-biweekly WACE (QB-WACE) anomalies and depends on the NAO+ and North Atlantic conditions by classifying the UB based on a case study of a cold event that occurred over southern China in January 2008. A composite analysis during 1979-2013 shows that the QB-WACE anomalies associated with the UB that often occur with the NAO+ are strong and influenced by the North Atlantic jet (NAJ) and zonal wind strengths over Eurasia. For NAO+-related UB, the QB-WACE anomaly depends strongly on the location of UB, and the UB anomalies lag the NAO+ by approximately 4-7 days. The strength of the NAJ determines whether the combined NAO+ and UB anomalies exhibit a negative East Atlantic/West Russia (EA/WR-) pattern, while the region of weak zonal winds over Eurasia and the zonal extent of the NAJ dominate the location of UB. For southward-, eastward-, and westward-displaced UBs associated with a strong NAJ, the NAO+ favors the UB with a southward-displaced QB-WACE anomaly through wave train propagation like an EA/WR- pattern. Eastward- and southward-displaced UB anomalies induce similarly displaced cold anomalies with intrusion into southern China. However, for a northward-displaced UB, this happens without pronounced EA/WR− patterns because of a weak NAJ and is accompanied by a northward-displaced QB-WACE anomaly.

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document

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http://n2t.net/ark:/85065/d7c82bwv

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eng

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geoscientificInformation

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publication

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2016-01-01T00:00:00Z

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2016-06-01T00:00:00Z

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Copyright 2016 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.

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OpenSky Support

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UCAR/NCAR - Library

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PO Box 3000

Boulder

80307-3000

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opensky@ucar.edu

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http://opensky.ucar.edu/

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