Simulation of non-hydrostatic gravity wave propagation in the upper atmosphere

Abstract

Abstract. The high-frequency and small horizontal scale gravity waves may be reflected and ducted in non-hydrostatic simulations, but usually propagate vertically in hydrostatic models. To examine gravity wave propagation, a preliminary study has been conducted with a global ionospherethermosphere model (GITM), which is a non-hydrostatic general circulation model for the upper atmosphere. GITM has been run regionally with a horizontal resolution of 0.2 • long × 0.2 • lat to resolve the gravity wave with wavelength of 250 km. A cosine wave oscillation with amplitude of 30 m s −1 has been applied to the zonal wind at the low boundary, and both high-frequency and low-frequency waves have been tested. In the high-frequency case, the gravity wave stays below 200 km, which indicates that the wave is reflected or ducted in propagation. The results are consistent with the theoretical analysis from the dispersion relationship when the wavelength is larger than the cutoff wavelength for the non-hydrostatic situation. However, the low-frequency wave propagates to the high altitudes during the whole simulation period, and the amplitude increases with height. This study shows that the non-hydrostatic model successfully reproduces the high-frequency gravity wave dissipation.

Thermospheric mass density: A review

“…This implies that the hydrostatic assumption (which precludes such waves) can underestimate the upper thermospheric density response to rapid changes in energy input. The hydrostatic assumption also alters the dispersion relation for high-frequency gravity waves with horizontal wavelengths less than 4πH, where H is the scale height (Akmaev, 2011, section 4.5;Deng and Ridley, 2014b). Deng et al (2008b) pointed out the importance of accounting for height-dependent gravity in thermospheric models, given that gravitational acceleration decreases by about 10% between 100 and 400 km.…”

“…Sources are similar to those of gravity waves: wind/topography interaction in the troposphere (Walterscheid and Hickey, 2005), interfering ocean waves (Rind, 1977), seismic activity, and localized auroral heating in the high-latitude thermosphere (Wilson, 2012;Pasko, 2012;Deng and Ridley, 2014b). Rind (1977) estimated that 0.2 Hz ocean-generated waves deposit about as much energy into the thermosphere as gravity waves do.…”

“…The waves propagated from the source to the thermosphere in about 30 min, where they caused density perturbations of up to 11%. Deng and Ridley (2014b) found that disturbances produced by Joule heating near 130 km altitude can propagate rapidly upward in the form of an acoustic wave and result in upper thermospheric density enhancements of ~50%.…”

Effects of Energetic Electron and Proton Precipitations on Thermospheric Nitric Oxide Cooling During Shock‐Led Interplanetary Coronal Mass Ejections

“…Global Ionosphere-Thermosphere Model (GITM; Ridley et al, 2006) is a three-dimensional global circulation model for the upper atmosphere. Different from most of the conventional circulation models, GITM relaxes the hydrostatic assumption, has flexible grid resolutions, and short time steps of~2 s. These features make, for example, realization of acoustic-gravity waves (Deng et al, 2008;Deng & Ridley, 2014;Lin et al, 2017;Lin, Deng, & Ridley, 2018), possible. A new photochemistry module was added to GITM for better accounting for the production of NO via meta-state of nitrogen and secondary electrons/photoelectrons to investigate the sensitivity of the global NO cooling power at various solar and geomagnetic activity levels (Lin, Deng, Venkataramani, et al, 2018).…”

A study of the nonlinear response of the upper atmosphere to episodic and stochastic acoustic‐gravity wave forcing

“…Using its neutral atmospheric output to drive a self‐consistent ionosphere model, Zettergren and Snively [, ] have also investigated the ionospheric response to acoustic waves generated by sources of different spatial and temporal scales. The necessity of including compressibility in the GW calculation without hydrostatic assumption is also demonstrated by the GCM results [ Deng et al ., ; Deng and Ridley , ]. Meanwhile, hemispheric coupling of the ionospheric response to lower atmospheric perturbations is observed in the SAMI3 (Sami3 is Also a Model of the Ionosphere) simulations [ Huba et al ., ].…”