Recurrent Climate Winter Regimes in Reconstructed and Modeled 500 hPa Geopotential Height Fields over the North Atlantic/European sector 1659-1990
Casty C, Handorf D, Raible CC, Gonzalez-Rouco JF, Xoplaki E, Luterbacher J, Weisheimer A, Dethloff K, Wanner H
CLIMATE DYNAMICS
submitted Feb 2004


Abstract: Recurrent climate winter (DJF) regimes are examined from statistically reconstructed and modeled 500 hPa geopotential height fields over the North Atlantic/European sector for the period 1659--1990. We investigated the probability density function (PDF) of the state space spanned by the first two Empirical Orthogonal Functions (EOF) of combined winter data. Regimes are detected as patterns that correspond to areas of the state space with an unexpected high recurrence probability using a Monte Carlo (MC) approach. The reconstruction and the model reveal four recurrent climate regimes. They correspond to the two phases of the North Atlantic Oscillation (NAO) and two opposite blocking patterns. It is concluded that the reconstructed and the modeled data for this geographic sector reproduce low-frequency atmospheric variability in the form of regime-like behavior. The modeled data show higher capability in reproducing recurrent climate regimes than the reconstruction. However, there is evidence that the reconstructed data reflect past atmospheric conditions more realistic.

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Addresses:
Casty, C.,Xoplaki E., Luterbacher J., Wanner, H., Institute of Geography, University of Bern, Hallerstr. 12, CH-3012 Bern, Switzerland.
Handorf, D., Weisheimer, A., Dethloff K., Alfred Wegener Institute for Polar and Marine Research, Telegrafenberg A43, D-14473 Potsdam, Germany.
Raible C.C., Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstr. 5, CH-3012 Bern, Switzerland.
Gonzalez-Rouco, J.F., Department of Astrophysics and Atmospheric Sciences, University of Madrid, Ciudad Universitaria 28040, Spain.

Reprints (after having been accepted):
Raible CC, Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland, raible@climate.unibe.ch