Lidar observation of gravity and tidal waves in the stratosphere and mesosphere

Abstract

Lidar measurements of atmospheric density and temperature in the altitude range 30‐to 80 km have been performed during the last 2 years from the Observatory of Haute‐Provence (latitude 44°N, longitude, 6°E). The potential of this technique for studying the middle atmospheric structure is presented and preliminary results on wave propagation are discussed. It is shown that wave‐like structures are observed systematically in this height range. Fourier analysis indicates that most of the energy is transported by waves of vertical wavelengths on the order of 8 to 15 km. The amplitude of the density variations is shown to follow a ρ −l/2 law up to 70 km. The characteristics of the observed density waves suggest that they are caused by a superposition of internal gravity waves propagating upward from the troposphere and a diurnal tide component in the range 30–50 km. Such waves are able to induce quite significant perturbations in atmospheric density and therefore temperature on an hourly basis. The Lidar technique is able to monitor those variations for the first time from a ground station operating continuously.