  Earth's atmosphere is in a state far from thermodynamic equilibrium. For
example, the large scale equator-to-pole temperature gradient is maintained by
tropical heating, polar cooling, and a midlatitude meridional eddy heat flux
predominantly driven by baroclinically unstable weather systems. Based on basic
thermodynamic principles, it can be shown that the meridional heat flux, in
combination with the meridional temperature gradient, acts to maximize entropy
production of the atmosphere. In fact, maximum entropy production (MEP) has
been successfully used to explain the observed mean state of the atmosphere and
other components of the climate system. However, one important feature of the
large scale atmospheric circulation is its often non-Gaussian variability about
the mean. This paper presents theoretical and observational evidence that some
processes in the midlatitude atmosphere are significantly non-Gaussian to
maximize entropy production. First, after introducing the basic theory, it is
shown that the skewness of sea surface winds, damped by nonlinear surface drag,
are consistent with the MEP principle. Then it is pointed out that the observed
wavenumber spectrum of long planetary waves in the midlatitudes can be roughly
explained by maximizing the meridional eddy heat flux (and related entropy
production) of unstable baroclinic Eady waves. Finally observational evidence
is presented that the meridional eddy heat flux is increased by non-Gaussian
variability in meridional wind and temperatures anomalies.
