Time-frequency analysis of backscattered lidar signal to study atmosphere dynamics

Lidar is a laser beam which sends vertically monochromatic pulses into the atmosphere. The analysis of the backscattered light provides information about the vertical structure, composition and density of the atmosphere versus height. The temperature profile is deduced from the recorded density profile. Temperature perturbations are associated with gravity wave phenomena. It is now widely recognized that atmospheric gravity waves play a major role in determining the large scale circulation and structure of the middle atmosphere. The aim of the study is to identify characteristics of these particular waves (vertical wavelength, height...) above Reunion island. Different perturbation signals are analysed with an usual parametric time-frequency tool and a comparison is made for two representative periods