A method for evaluating the modes of variability in general circulation models

Simon Grainger, Carsten S Frederiksen, Xiaogu Zheng


The seasonal mean of an atmospheric climate variable is considered to be a statistical random variable with two components: a slow component related to slowly varying forcing from external and internal atmospheric sources (time scale of a season or more), and an intraseasonal component related to forcing from weather variability with time scale less than a season. Here, a method is proposed to compare the modes of variability obtained from eigenvalue decomposition of the slow and intraseasonal covariance matrices estimated from reanalysis data with modes of variability estimated from a set of coupled general circulation models. As an example, the method is applied to the Southern Hemisphere summer 500hPa geopotential height for the period 1951--2000. The method is applicable to many other atmospheric climate variables and datasets.

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DOI: http://dx.doi.org/10.21914/anziamj.v50i0.1431

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