Gravity waves and forecast errors
 

Interesting paper phaps relevant to present discussions-
GEOPHYSICAL RESEARCH LETTERS, VOL. 30, NO. 24, 2255, doi:10.1029/2003GL018498, 2003
Spontaneous generation and impact of inertia-gravity waves in a stratified, two-layer shear flow
P. D. Williams and P. L. ReadT. W. N. Haine
Abstract
[1] Inertia-gravity waves exist ubiquitously throughout the stratified parts of the atmosphere and
ocean. They are generated by local velocity shears, interactions with topography, and as geostrophic
(or spontaneous) adjustment radiation. Relatively little is known about the details of their
interaction with the large-scale flow, however. We report on a joint model/laboratory study of a
flow in which inertia-gravity waves are generated as spontaneous adjustment radiation by an evolving
large-scale mode. We show that their subsequent impact upon the large-scale dynamics is generally
small. However, near a potential transition from one large-scale mode to another, in a flow which is
simultaneously baroclinically-unstable to more than one mode, the inertia-gravity waves may strongly
influence the selection of the mode which actually
occurs.
preprint online at-
http://www.jhu.edu/~eps/faculty/haine/
In essence-in a rotating,two layer,'dish pan' experiment and numerical simulations it's found that
,in certain regimes,the presence of gravity wave 'noise' can affect the mode and evolution of
'large scale' Rossby waves.The implication is that in order to properly forecast the the motion and
timing of Rossby Waves (the Long waves that control synoptic systems) it's necessary to either model
the GWs explicitly or use a nonlinear or stochastic parameterisation ie inject noise into the
model.(Prob goes against the grain for most NWP modellers).
Speculation- does the ubiquitous presence of GWs near jet streams seriously affect forecast errors
(as well as problems with initial conditions)?

--
regards,
david
(add 17 to waghorne to reply)