Vertical distribution of gravity wave potential energy from long-term Rayleigh lidar data at a northern middle-latitude site

International audienceIn this paper, we use the Rayleigh lidar in order to give an overview of the gravity wave activity at a northern middle latitude station, at Haute-Provence Observatory (43.93°N, 5.71°E). In order to have access to perturbations with short time and vertical scales, at least in a statistical sense, we analyse raw lidar signals with a variance method. 16 years of lidar datasets are analyzed in this study. The results of the variability, climatology and seasonal changes are reported. We observe night-to-night variability in gravity wave potential energy, which follow a log-normal distribution with a standard deviation ranging between 0.50 to 0.58 (base 10 logarithm). A monthly distribution of gravity waves is also obtained in the upper stratosphere and mesosphere. In the 30-50 km altitude range (the upper stratosphere), an annual cycle is clearly found with a maximum in winter and a minimum in summer. An annual cycle in the lower mesosphere is also observed with maximum in winter. In the upper mesosphere, a semi-annual cycle is found at ~75 km. At this altitude, the maximum gravity wave activity occurs in winter and in summer. A more pronounced summer maximum is observed (+25%). The summer maximum at OHP in the upper mesosphere is probably due to oblique propagation. Looking at the seasonally averaged profiles, it is possible to observe the preferential altitudes of energy dissipation. Gravity waves are dissipating above ~70 km during all seasons, but there is relatively little dissipation at lower altitudes