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. References
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