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Advances in Meteorology
Volume 2011 (2011), Article ID 717812, 11 pages
http://dx.doi.org/10.1155/2011/717812
Research Article

Blocking Detection Based on Synoptic Filters

Meteorologisches Institut, KlimaCampus, University of Hamburg, Grindelberg 5, 20144 Hamburg, Germany

Received 26 December 2010; Revised 1 March 2011; Accepted 21 March 2011

Academic Editor: Hann-Ming Henry Juang

Copyright © 2011 Bernd Schalge et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The Tibaldi-Molteni blocking index is supplemented by additional filter criteria to eliminate cut-off lows and subsynoptic structures. We introduce three blocking filters and analyse their sensitivities: (i) a quantile filter requiring a minimum geopotential height anomaly to reject cut-off lows, (ii) an extent filter to extract scales above a minimum zonal width, and (iii) a persistence filter to extract events with a minimum duration. Practical filter application is analysed in two case studies and the blocking climatologies for the Northern and the Southern Hemisphere.