Evaporation and Humidity Profiles for Neutral Conditions over Rugged Hilly Terrain

Abstract

An analysis was made of vertical profiles of mean specific humidity in the hilly pre-Alpine region in Switzerland under conditions of new neutral atmospheric stability. The profile data were derived from radiosonde observations during the summer season of 1982. A logarithmic layer was found to extend from approximately 2h to 6h [where h(=95 m) is the mean height of the hills]. The zero-plane displacement height for water vapor d_0ν appeared to be close to that for momentum, i.e., about 50 m; on the other hand, the water vapor roughness height z_0ν for those ascents with a wet surface was found to be around 10 to 15 times smaller than the momentum roughness z₀(=3.8 m). The values of evaporation, deduced from the humidity profiles with the friction velocity of the corresponding velocity profiles, were very close to those measured with a lysimeter.