Lidar Monitoring of water vapor and comparison with numerical simulations.

A solar blind Raman (SBR) lidar based on a KrF excimer laser (248 nm)has been used to continuously monitor the water vapor mixing ratio in the lower troposphere and it is shown once more that the SBR lidar is a valuable tool for day and night-time studies of the fine strucure often seen in water vapour profiles. The lidar measurements of water vapour have been used to assess the performance of atmospheric boundary layer oriented mesoscale simulations. The Regional Atmospheric Modeling Systae (RAMS) has been used to simulate the circulation patterns and the planetary boundary layer structure over the Sallentum peninsula of Italy. Numerical simulations with different grid nesting, initialisation conditions and surface information details have been tested and a satisfactory agreement between experimental and numerical water vapour profiles has been observed. It is shown that the sensitivity of water vapour profiles to the mixing height and surface advection effects can be successfully used for a proper testing of models especially in coastal areas and non-homogeneous terrain.