Parameterization of the effects of vertically propagating gravity waves for thermosphere general circulation models: Sensitivity study

Abstract

[1] A parameterization of gravity wave (GW) drag, suitable for implementation into general circulation models (GCMs) extending into the thermosphere is presented. Unlike existing schemes, the parameterization systematically accounts for wave dissipation in the upper atmosphere due to molecular viscosity, thermal conduction, ion friction, and radiative damping in the form of the Newtonian cooling. This is in addition to using the commonly employed breaking/saturation schemes, based on either linear Hodges-Lindzen instability criteria or its nonlinear extension to multipleharmonic spectra. The scheme was evaluated in a series of tests of increasing complexity. In the thermosphere, the simulations suggest that the dissipation competes with the instability caused by amplitude growth, and can seriously alter GW propagation and the associated wave drag. Above the mesopause the GW drag is generally created by harmonics with fast horizontal phase velocities, which under favorable conditions can propagate into the F 2 layer. The effects of thermospheric dissipation are more complex than a simple exponential decay of GW fluxes above certain levels. We examine the sensitivity of the GW drag profiles to the variations of the source spectra typically employed in GCMs. These results suggest that GWs can provide strong coupling between the meteorological events in the lower atmosphere and the circulation well above the middle atmosphere.

El Niño influence on the mesosphere/lower thermosphere circulation at midlatitudes as seen by a VHF meteor radar at Collm (51.3 ° N, 13 ° E)

“…Gravity waves in the middle atmosphere are parameterized based on an updated linear Lindzen (1981) scheme. For the thermosphere, an approach after Yigit et al (2008) is chosen, which especially accounts for the conditions in the thermosphere such as molecular viscosity, thermal conduction, ion friction, and radiative damping in the form of the Newtonian cooling. Thermosphere results are, however, not considered here.…”

A dominant acoustic-gravity mode in the polar thermosphere

“…Using an extended gravity wave scheme (Yigit et al, 2008) that accounts for realistic wave propagation and dissipation showed that lower atmospheric gravity waves propagate into the thermosphere and affect the general circulation of the high-latitude thermosphere under various conditions (Yigit et al, 2009(Yigit et al, , 2012(Yigit et al, , 2014. Also, numerical simulations suggest that gravity waves propagate from the surface to the thermosphere (Hickey et al, 2009(Hickey et al, , 2010.…”

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

“…If its amplitude is large enough, it may first undergo wavebreaking (Fritts and Lund, 2011) or wave-wave interactions (Yigit et al, 2008(Yigit et al, , 2009). These processes result in momentum and energy deposition in the thermosphere, which can result in a change in the background neutral wind and temperature (VF06; Becker and Fritts, 2006;Yigit et al, 2008Yigit et al, , 2009Fujiwara, 2008, 2009;Vadas andLiu, 2009, 2011;Yigit and Medvedev, 2010).…”

“…These processes result in momentum and energy deposition in the thermosphere, which can result in a change in the background neutral wind and temperature (VF06; Becker and Fritts, 2006;Yigit et al, 2008Yigit et al, , 2009Fujiwara, 2008, 2009;Vadas andLiu, 2009, 2011;Yigit and Medvedev, 2010). Such GWs can also affect the ionosphere (e.g., Klostermeyer, 1972;Hocke and Schlegel, 1996;Hickey et al, 2009Hickey et al, , 2010.…”