[Stoch] Paper on stochastic Gravity Waves parameterization

LOTT Francois flott at lmd.ens.fr
Wed Jun 6 06:48:55 MDT 2012

Dear colleagues,

here is one paper on gravity waves parameterization
I would like to circulate in our stochastic community!

Best regards,

Francois Lott

A stochastic parameterization of non-orographic gravity waves: Formalism 
and impact on the equatorial stratosphere

F. Lott, L. Guez, and P. Maury

A formalism is proposed to represent a broadband spectrum of Gravity 
Waves (GWs) via the superposition of a large ensemble of statistically 
independent monochromatic ones. To produce this large ensemble at a 
reasonable numerical cost, we use the fact that the life cycles of the 
waves needed to be parameterized in General Circulation Models (GCMs) 
have time scales that largely exceed the time step of the model. We can 
therefore launch few waves with characteristics chosen randomly at each 
time step, and make them having an effect on a longer time scale by 
applying an AR1 relation between the gravity waves drag at a given time 
and that at the next time step. The stochastic GW parameterization is 
applied to a GCM in the tropics, and its additional drag causes a 
realistic Quasi-Biennial Oscillation (QBO). The more realistic wind 
structure also results in a better representation of the large scale 
equatorial waves, like the Rossby Gravity Waves (RGWs) with periods 
around 4--5 day.


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