Mesoscale basin flows in the nocturnal boundary-layer: modeling and verification

During the night, in conditions of slack pressure gradients and clear skies, the boundary layer becomes shallow and strongly stably stratified. For significant orography, slope and katabatic flows setup that can be the main meteorological features during night, controlling the rate of cooling at the surface.These currents organise at the scale of the hydrographical basin, especially if the latter is relativelly small.

A mesoscale simulation for the island of Majorca in the western mediterranean sea is presented here. The vertical resolution is very high close to the ground, allowing for a good representation of the flows at the basin and the island scales, with characteristic scales of 20 and 100 km respectively. Special effort is made on the verification of the structures, through comparison with in-situ observations, but mainly to imaging obtained from the NOAA and the Meteosat-second generation satellites. This allows respectively to check the realism of the spatial structures and of the temporal evolution of the simulation.