Analysis of the mid-latitude weather regimes in the 200-year control integration of the SINTEX model

S. Corti, S. Gualdi, A. Navarra


Recent results indicate that climate predictions require models which can simulate accurately natural circulation
regimes and their associated variability. The main purpose of this study is to investigate whether (and how) a
coupled model can simulate the real world weather regimes. A 200-year control integration of a coupled GCM
(the «SINTEX model») is considered. The output analysed consists of monthly mean values of Northern Hemisphere
extended winter (November to April) 500-hPa geopotential heights. An Empirical Orthogonal Function (EOF)
analysis is first applied in order to define a reduced phase space based on the leading modes of variability. Therefore
the principal component PDF in the reduced phase space spanned by two leading EOFs is computed. Based on a
PDF analysis in the phase space spanned by the leading EOF1 and REOF2, substantial evidence of the nongaussian
regime structure of the SINTEX northern winter circulation is found. The model Probability Density
Function (PDF) exhibits three maxima. The 500-hPa height geographical patterns of these density maxima are
strongly reminiscent of well-documented Northern Hemisphere weather regimes. This result indicates that the
SINTEX model can not only simulate the non-gaussian structure of the climatic attractor, but is also able to
reproduce the natural modes of variability of the system.


Coupled General Circulation Model;systematic error;non-linear dynamics;flow regimes

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X