Interaction entre la couche limite d'Ekman sous un ecoulement de maree et une couche limite contiere, et instabilites barotropes

Strong tidal currents generate in coastal waters a number of phenomena which are not taken into account by mesoscale modelling. These are related to: the Coriolis effects on horizontal turbulence; the bottom boundary layer effect modified by the rotation of the earth and depth variations. Schematic experiments to demonstrate these effects have been done on the large rotating table in Grenoble. We describe the experiments and the preliminary results obtained with permanent and alternative currents. The experiments were conducted along the wall of a horizontal flat-bottom cylindrical rotating tank, respecting the Froude, Ekman and Rossby similitudes

Physical modelling of baroclinic development in the lee of the Alps

When baroclinic development is triggered by an obstacle, like an extended mountain range, the so-called lee, or secondary cyclogenesis can develop. The presence of the obstacle exerts a blocking effect on the lower layers of the impinging airflow, forcing them to go round its borders and reach the lee region with a delay. Blocking and delay are both responsible for the initial pressure decrease downwind of the mountain and for the subsequent proper downstream baroclinic development. According to this rather simple scheme, a cyclogenesis episode in the lee of the Alps was simulated in a hydraulic turntable. The results of these experiments showed a good agreement, both from a qualitative and quantitative point of view, with the analysis of an episode of lee cyclogenesis coupled to a cold outbreak in the Mediterranean, which actually occured in Southern Europe downstream of the Alps

Physical modelling of baroclinic development in the lee of the Alps

When baroclinic development is triggered by an obstacle, like an extended mountain range, the so-called lee, or secondary cyclogenesis can develop. The presence of the obstacle exerts a blocking effect on the lower layers of the impinging airflow, forcing them to go round its borders and reach the lee region with a delay. Blocking and delay are both responsible for the initial pressure decrease downwind of the mountain and for the subsequent proper downstream baroclinic development. According to this rather simple scheme, a cyclogenesis episode in the lee of the Alps was simulated in a hydraulic turntable. The results of these experiments showed a good agreement, both from a qualitative and quantitative point of view, with the analysis of an episode of lee cyclogenesis coupled to a cold outbreak in the Mediterranean, which actually occured in Southern Europe downstream of the Alps