Recurrent climate winter regimes in reconstructed and modelled 500 hPa geopotential height fields over the North Atlantic/European sector 1659-1990

Recurrent climate winter regimes are examined from statistically reconstructed and modelled 500 hPa geopotential height fields over the North Atlantic/ European sector for the period 1659-1990. We investigate the probability density function of the state space spanned by the first two empirical orthogonal functions 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 approach. The reconstruction and the model reveal four recurrent climate regimes. They correspond to the two phases of the North Atlantic Oscillation and two opposite blocking patterns. Complemented by the investigation of the temporal evolution of the climate regimes this leads to the conclusion that the reconstructed and the modelled data for this geographic sector reproduce low-frequency atmospheric variability in the form of regime-like behaviour. The overall evidence for recurrent climate regimes is higher for the model than for the reconstruction. However, comparisons with independent data sources for the period 1659-1990 revealed a more realistic temporal evolution of the regimes for the reconstructed data.