Simulation of lidar measurements of gravity waves in the mesosphere

Lidar measurements of mesospheric gravity wave characteristics are simulated using a simple numerical model. Simple theory is used to superimpose gravity wave fluctuations upon typical background densities and sodium abundances in the height range 80-100 km, which we then assume are perfectly observed by a Rayleigh and Na lidar, respectively. These lidar ''data'' are then analyzed for their gravity wave content using the standard reduction and analysis methods which are routinely applied to these data sets. Our goal is to assess whether this analysis of lidar data faithfully recovers the underlying wave field. In both quasi-monochromatic and spectral wave studies, the height range over which Na number density can be measured and the shape of the background Na profile impose a Limit on the gravity wave information which can be extracted from Na lidar data. The Limitations due to background layer shape do not exist for Rayleigh lidar measurements. The simulations reveal that quasi-monochromatic gravity waves with vertical wavelengths larger than approximately 10 km may not be reliably retrieved from Na lidar data. It is also shown that there are limitations on the accurate extraction of spectral parameters from Na lidar data due to the limited vertical extent of the mesospheric Na layer.