Forced gravity wave response near the jet exit region in a linear model

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Abstract

This study investigates the propagation of gravity waves in the region of significant horizontal and vertical shear associated with a localized atmospheric jet using a linear model. Gravity waves are produced in the linear model by imposing prescribed divergence/convergence forcing of various scales near the core of an idealized local jet. The spatial structures of these forced gravity waves are nearly steady after a few inertial periods, despite the amplitudes slowly increasing with time.

Linear model simulated wave response to prescribed forcing shows limited dependence on the scales of the forcing. It is found that the wave structure (e.g. horizontal/vertical wavelengths, phases and locations) away from the forcing are largely constrained by the environmental wind shear through the wave capture mechanism. Consequently, simulated gravity wave activities have the tendency to be focused on the vicinity where the line of constant shear aspect ratio approximates to the characteristic large-scale environmental aspect ratio (f/N). Ray tracing analysis is further used to demonstrate that wave capturing is the consequence of different influences of the horizontal and vertical shears upon longer and shorter waves. Copyright © 2010 Royal Meteorological Society

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