Local mean state changes due to gravity wave breaking modulated by the diurnal tide

Abstract

Abstract. During gravity wave breaking, heating rates are determined by wave advection, turbulent diffusion, and turbulence dissipative heating. A series of numerical experiments show that the total heating rates can be larg (--• +10 Kh -1) and can cause large local temperature changes. The wave advection causes dynamical cooling in most of the wave breaking region, consistent with previous studies. Nonuniform vertical turbulent diffusion causes strong transient heating in the lower part of the wave breaking region and cooling above. The dissipative heating rate is relatively small compared with those due to the dynamical cooling and turbulent diffusion. In these numerical experiments, zonal wind and temperature perturbations of the diurnal tide and the zonal mean zonal wind and temperature compose the background state for the computation. This is used to examine the idea that temperature inversions, often observed in the mesosphere, are related to the gravity wave and tidal wave interactions. The simulation results show that the large temperature changes in this process can form temperature inversion layers that progress downward with a speed similar to that of a diurnal tide phase speed, which clearly suggests the tidal modulation of the gravity wave and mean flow interactions. Such a process is dependent on season and latitude, because the background state stability varies with season and latitude. The development of the temperature inversion is also affected by the gravity wave characteristics. It is also shown that the local mean wind, wind shear, and chemical species can undergo large changes accompanying the temperature inversion.

Statistical characteristics of PMWE observations by the EISCAT VHF radar

“…Lidar observations at mid-latitudes by Whiteway et al (1995); Thomas et al (1996); Liu et al (2004) and high-latitudes by Cutler et al (2001); Duck and Greene (2004); Collins et al (2011) have shown that MILs are often associated with turbulence activity which is reflected in the lidar temperature measurements as an adiabatic lapse rate on top of the inversion layers. On the other hand, numerical simulations by Liu et al (2000) showed that vigorous turbulence is required to change the thermal structure to the shape associated with temperature inversions. Also, Thomas et al (1996) found a connection between MILs observed with Rayleigh lidar and winter radar echoes observed by their VHF radar, and concluded that the reason was strong turbulence activity.…”

Simultaneous observations of a Mesospheric Inversion Layer and turbulence during the ECOMA-2010 rocket campaign

“…Numerous observations show that temperature inversions are often associated with a near adiabatic lapse rates above the inversion layer (Whiteway et al, 1995;Duck et al, 2001), which is clearly indicative of turbulence activity in those regions. However, numerical simulations showed that only vigorous turbulence revealing heating rates of ∼ 10 K h −1 is capable of producing temperature inversions (Liu et al, 2000). Such strong turbulence, however, has rarely been observed (see, e.g., Lübken, 1997;Lübken et al, 2002) in contrast to the temperature inversion layers, which are common phenomena.…”

Observations and Modeling of the Upper Mesosphere: Mesopause Characteristics, Inversion Layers, and Bores

“…This is important for several reasons, among which are the fact that a large-scale TIL may comprise a stable duct for longdistance propagation of gravity waves, and/or support mesospheric undular bores . This may also shed some light on the role of gravity waves in producing TILs [Huang et al, 1998;Liu et al, 2000]. We therefore sought layers that were similar in amplitude and altitude within sequences of consecutive events.…”