Numerical modeling study of the momentum deposition of small amplitude gravity waves in the thermosphere

The model solves the nonlinear propagation and dissipation of a GW packet from the stratosphere into the thermosphere with realistic molecular viscosity and thermal diffusivity for various Prandtl numbers. The numerical simulations are performed for GW packets with initial vertical wavelengths (z) ranging from 5 to 50 km.

We show that z decreases in time as a GW packet dissipates in the thermosphere, in agreement with the ray trace results of Vadas and Fritts (2005) (VF05). We also find good agreement for the peak height of the momentum flux (zdiss) between our simulations and VF05 for GWs with initial z 2 H in an isothermal, windless background, where H is the density scale height. We also confirm that zdiss increases with increasing Prandtl number.