| Air-sea fluxes of heat and moisture contain structures too small to be explicitly resolved by
global coupled atmosphere-ocean general circulation models (GCMs). In the air-sea moisture
flux, for example, small-scale precipitation structures could be caused by unresolved clouds
and small-scale evaporation structures could be caused by unresolved turbulence in the
surface wind field.
In an attempt to capture the climatic impacts of such structures, coupled GCM
experiments are performed in which the air-sea fluxes are stochastically perturbed. Stochastic
approaches are used increasingly widely by climate modellers (e.g. Palmer and Williams,
2008). The stochasticity impacts significantly upon the simulated mean climate, especially in
the tropics. A physical mechanism to explain the impacts is proposed: the ocean responds
asymmetrically to random positive and negative surface buoyancy perturbations,
systematically deepening the mixed layer, cooling the equatorial surface ocean, and
weakening the atmospheric Hadley circulation. The experiments therefore yield a new
mechanistic understanding of the detailed climatic impacts of stochastic air-sea
fluxes.
Reference
Tim Palmer and Paul Williams (Editors), Stochastic Physics and Climate Modelling, special
issue of Philosophical Transactions of the Royal Society A, 366(1875), pp 2419–2641, 2008.
http://publishing.royalsociety.org/stochastic-climate |