Channeling and countercurrent in the upper Rhine Valley: numerical simulations.

Abstract

In the upper Rhine Valley, located in the southwest part of the Federal Republic of Germany, a pronounced channelling of the airflow was observed and occasionally also a countercurrent, although the valley is very flat and very broad (35 km) and its boundary mountains are no more than 500 m above the valley floor. Both channelling and countercurrents were simulated numerically with the nonhydrostatic mesoscale model FITNAH. These simulations were carried out for steady state conditions in a moderately stable stratified atmosphere for five different directions of the geostrophic wind (W, WNW, NW, NNW and N; the orientation of the valley is south to north). The results are shown by maps with streamlines at 30 m above ground by vertical cross sections and by three dimensional trajectories. (A)