Estimates of the North Atlantic Oscillation back to 1692 using a Paris-London westerly index

Cornes, Richard C., Jones, Philip D. ORCID:, Briffa, Keith R. and Osborn, Timothy J. ORCID: (2013) Estimates of the North Atlantic Oscillation back to 1692 using a Paris-London westerly index. International Journal of Climatology, 33 (1). pp. 228-248. ISSN 1097-0088

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A westerly index for Europe is developed back to 1692 using newly recovered and corrected Mean Sea-level Pressure (MSLP) data from London and Paris. The index is compared against various instrumental and proxy indices of the North Atlantic Oscillation (NAO). In the winter, the Paris-London index depicts a spatial pattern of atmospheric circulation that is bi-modal, with centres of action that are shifted eastwards compared to the NAO. Owing to asymmetry in the NAO the Paris-London index provides a good depiction of positive NAO conditions as well as extreme negative phases of the NAO that arise from reversals of the pressure centres, but less extreme negative NAO conditions are associated with westerly index values approaching zero. The merit in using the Paris-London index lies with its consistency over time as a measure of westerly wind flow, which may not be the case with other proxy-based indices. In the summer, the Paris-London index bears a close relationship to the reconstructed high-summer NAO series of Folland et al. (2009) as well as the summer Luterbacher et al. (1999) NAO reconstruction. An important finding is that the summer NAO was highly variable during the early nineteenth century but was predominately positive on the decadal time scale during that period. Since circa 1970 the summer index has mostly been negative, indicating reduced westerlies and increased blocking conditions that are exceptional in the context of the last 250 years. Copyright © 2012 Royal Meteorological Society

Item Type: Article
Faculty \ School: Faculty of Science > School of Environmental Sciences
University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups: Faculty of Science > Research Groups > Climatic Research Unit
Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Faculty of Social Sciences > Research Centres > Water Security Research Centre
Depositing User: Users 2731 not found.
Date Deposited: 05 Mar 2012 13:29
Last Modified: 15 Jun 2023 23:35
DOI: 10.1002/joc.3416

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