Combination of Lidar and Model Data for Studying Deep Gravity Wave Propagation

Abstract

The paper presents a feasible method to complement ground-based middle atmospheric Rayleigh lidar temperature observations with numerical simulations in the lower stratosphere and troposphere to study gravity waves. Validated mesoscale numerical simulations are utilized to complement the temperature below 30-km altitude. For this purpose, high-temporal-resolution output of the numerical results was interpolated on the position of the lidar in the lee of the Scandinavian mountain range. Two wintertime cases of orographically induced gravity waves are analyzed. Wave parameters are derived using a wavelet analysis of the combined dataset throughout the entire altitude range from the troposphere to the mesosphere. Although similar in the tropospheric forcings, both cases differ in vertical propagation. The combined dataset reveals stratospheric wave breaking for one case, whereas the mountain waves in the other case could propagate up to about 40-km altitude. The lidar observations reveal an interaction of the vertically propagating gravity waves with the stratopause, leading to a stratopause descent in both cases. * Current affiliation: Deutsches Zentrum für Luft-und Raumfahrt,

Evaluation of methods for gravity wave extraction from middle-atmospheric lidar temperature measurements

“…A possible mechanism is that mountain waves with very large amplitudes become unstable at these altitudes and break. This has for example been observed by Ehard et al (2015), who detected a self-induced critical layer around 30 km altitude caused by a strong mountain wave event above northern Scandinavia.…”

“…Atmospheric gravity waves are well known to have a strong impact on the middle-atmospheric circulation (e.g., Holton and Alexander, 2000;Fritts and Alexander, 2003). By transporting energy and momentum from the lower atmosphere into the middle atmosphere, they are responsible for the formation of the cold polar summer mesopause (e.g., Lindzen, 1981).…”

On the influence of zonal gravity wave distributions on the Southern Hemisphere winter circulation

“…The large amplitudes at equatorial latitudes are caused by convection. In the Northern Hemisphere (NH) winter there is a significant orographic GW source located above Scandinavia (e.g., Ehard et al, 2016). As stated above, very intense GW activity has been found in the Southern Hemisphere (SH) to the east of the Andes mountains and the Antarctic Peninsula, which is mainly caused by topography (Eckermann et al, 1999;P.…”

Secondary Gravity Waves Generated by Breaking Mountain Waves Over Europe

“…The smaller vertical scale, at large amplitudes, lead to large vertical gradients in the wind and temperature structure of the wave, which can cause the mountain wave to break. The wave breaking creates turbulence and generates secondary acoustic‐gravity waves (Bacmeister & Schoeberl, ; Bossert et al, ; Ehard et al, ; Heale et al, ; Satomura & Sato, ; Smith et al, ; Vadas et al, ).…”