Foehn in the Rhine Valley as seen by a wind-profiler-RASS system and comparison with the nonhydrostatic model Meso-NH

Abstract

One of the scientific objectives of MAP (Mesoscale Alpine Programme) addressed the four-dimensional variability of the foehn flow in the Rhine Valley. Within the framework of the field program FORM (Foehn in the Rhine Valley during MAP) a unique observing network was deployed for 2.5 months. One of the ten intensive observing periods has been selected to illustrate the life cycle of a special foehn event, during which the descending of the warm foehn air and the erosion of the cold air pool was very pronounced. Thanks to the excellent resolution in time as well as in height of temperature and wind measured by a boundary layer wind profiler-RASS system it was possible to get a detailed picture of the evolution of this foehn event. Model simulations performed with the non-hydrostatic model Meso-NH are in good agreement with observations. It allows us to show the time evolution of the cold pool area along a distance of 50 km in the "Alpenrhein" Valley.