Airflow within major Alpine river valleys under heavy rainfall

This study documents the airflow within major Alpine river valleys in the presence of precipitation. The analysis seeks a conceptual understanding of the effect of rain on the valley flow. Ground-based and airborne Doppler radar and surface data from the Mesoscale Alpine Programme show that during persistent rainy periods the subsidence caused by melting and evaporation of precipitation particles contributes to the formation of a down-valley flow. This down-valley flow opposes moist southerly flow aloft, which is lifted over the topographic barrier and in which precipitation particles are formed.