CP Climate of the Past CP Clim. Past 1814-9332 Copernicus Publications Göttingen, Germany 10.5194/cp-4-147-2008 Shifts in early spring wind regime in North-East Europe (1955–2007) Keevallik S. 1 Soomere T. 2 Marine Systems Institute at Tallinn University of Technology, Akadeemia tee 21, 12618, Estonia Centre for Nonlinear Studies, Institute of Cybernetics at Tallinn University of Technology, Akadeemia tee 21, 12618, Estonia 04 08 2008 4 3 147 152 Copyright: © 2008 S. Keevallik 2008 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://cp.copernicus.org/articles/4/147/2008/cp-4-147-2008.html The full text article is available as a PDF file from https://cp.copernicus.org/articles/4/147/2008/cp-4-147-2008.pdf

Changes to the winter-to-spring switch-time of the upper air flow regime at the 850 and 500 hPa levels over the north-eastern Baltic Sea are analyzed based on a data set extending from 1955 to 2007. The long-term variation of the air flow in early spring (March) exhibits multiple regime shifts. The shifts are extracted by means of a vector analysis of the monthly mean air flow and using statistical shift detection technology. In the middle of the 1960s the average air flow turned from NW (WNW) to W (WSW) at the 500 (850) hPa level. The original regime was restored in the mid-1990s. The regime shifts in the average air flow in March can be interpreted as changes in the transition time from winter to summer circulation type.

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