The atmospheric boundary-layer structure within a cold air outbreak: Comparison of in situ, lidar and satellite measurements with three-dimensional simulations

A cold-air outbreak over the Mediterranean, associated with a Tramontane ev ent, has been simulated with the atmospheric non-hydrostatic model Mese-NH using a horizontal resolution of 2 km. Results are compared with in situ ai rcraft, airborne lidar and satellite measurements. On average, the mean and turbulent parameters simulated in the surface layer and mixed layer compar ed well with in situ measurements. The model was able to reproduce accurate ly the Foehn effect in the wake of Cape Creus, as well as the occurence of rolls in the coastal region in connection with cloud streets observed with AVHRR. Over the sea, the threshold value of turbulent kinetic energy defini ng the height of the atmospheric boundary-layer top in the model (defined a s 25% of the maximum turbulent kinetic energy in the profile) enables the s imulated atmospheric boundary-layer height to match the one retrieved from lidar measurements. Nevertheless, the model did not handle very well the ab rupt gradients of all meteorological parameters observed at the top of the atmospheric boundary-layer. Reasons for this are investigated.