Open AccessIs Blocking a Circulation Regime?
Author(s) -
Cristiana Stan,
David M. Straus
Publication year - 2007
Publication title -
monthly weather review
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.862
H-Index - 179
eISSN - 1520-0493
pISSN - 0027-0644
DOI - 10.1175/mwr3410.1
Subject(s) - blocking (statistics) , circulation (fluid dynamics) , climatology , anomaly (physics) , scale (ratio) , environmental science , potential vorticity , proxy (statistics) , vorticity , meteorology , geology , geography , mathematics , physics , statistics , vortex , mechanics , cartography , condensed matter physics
The relationship between Pacific blocking and large-scale circulation regimes is investigated. The large-scale circulation regimes are obtained by cluster analysis using the k-means method and tested against significance and reproducibility. Pacific blocking is described using two different methods. In a direct approach, blocking is described by a recently developed blocking index, which is defined in terms of potential temperature anomaly on a surface of constant potential vorticity. In an indirect approach, the occurrence of extreme events is used as a proxy for blockings. Between the two methods there is a causal relationship; the direct one is an indication of the occurrence of the blocking, while the indirect one is a measure of some of the effects caused by the blocking. The results indicate that large-scale circulation regimes are related to but not necessarily tightly coupled to blocking and weather extremes in the Pacific–North America region.