Cooling by melting precipitation in Alpine valleys: An idealized numerical modelling study

Abstract

Cooling by melting precipitation in Alpine valleys is investigated. In this case, the latent heat required for melting the falling snow is continuously removed from the valley air until the snowline reaches the valley bottom. Numerical simulations with a highly idealized two-dimensional model indicate an even smaller volume effect, which might be partly due to numerical inaccuracies. We also examined the impact of an air-mass exchange between the upper part of the valley atmosphere and the environment. Our results also suggest that resolving the turbulent eddies that form below the melting layer is important for realizing the volume effect, which implies that mesoscale numerical models with parametrized turbulence will systematically underestimate the cooling effect in Alpine valleys.