Abstract
Abstract. A Doppler lidar observation of an inertio-gravity wave in the mid-latitude lower stratosphere is presented. The wave packet characteristics (vertical and horizontal wavenumbers, intrinsic and apparent frequencies) are inferred from the analysis of the hodograph of the horizontal wind fluctuations. Those parameters are used as initial conditions for the calculation of the wave packet trajectory backwards in time in the atmosphere. These calculations are realized by ray-tracing techniques, with background fields (wind and stability) provided by the European Center for Medium-Range Weather Forecasting analyses. Sensitivity tests are performed in order to estimate the robustness of the computed trajectory. It is argued that the generation of the wave has taken place in the upper troposphere, where evidence of large synoptic scale Rossby wave disturbances are found. Our results support the fact that geostrophic adjustment (and possibly shear instabilities) associated with such disturbances could be an effective mechanism for the generation of inertia-gravity waves in the mid-latitude.Key words. Meteorology and atmospheric dynamics, mesoscale meteorology, waves and tides, instruments and techniques
Highlights
In the atmosphere, gravity waves are thought to be primarily generated in the troposphere
The general concern about ozone depletion in the mid-latitudes has raised the question of the polar vortex permeability, which is generally attributed to the interaction between Rossby waves and the background flow (e.g. Waugh et al, 1994; Bowman, 1996)
At 02:00 UTC on 3 September 1997 (t0) and at an altitude of 19.5 km (z0), a wave packet, whose initial characteristics are defined in Table 1, was launched
Summary
Gravity waves are thought to be primarily generated in the troposphere. In the upper stratosphere and mesosphere, criteria of static or dynamic instability may be reached so that the waves break and deposit their momentum and energy in the background flow This force (which generally acts as a drag) is crucial in maintaining the mean thermodynamic structure of the middle atmosphere: it is considered to be the driver of the merid-. Alexander and Rosenlof (1996) stated that general circulation models (GCM) lack an accelerating force to accurately represent the stratospheric jet This force may result from the breaking of non-stationary gravity waves. Danielsen et al (1991) noted the presence of fluctuations in ozone profiles near the vortex edge, which they attributed to the effects of an inertio-gravity wave. Vertical and horizontal displacements, induced by gravity waves, may contribute to the dispersion of tracers in the mid-latitude stratosphere (the so-called “surf zone”) (e.g. Teitelbaum et al, 1994, 1996; Gibson-Wilde et al, 1997; Eckermann et al, 1998)
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