Budgets of Water Vapor in the Unstable Boundary Layer over Rugged Terrain

Abstract

Inversion fluxes of water vapor are calculated for 11 clear days using profile data from a sequence of radio soundings over hilly terrain in the Pre-Alpine region of Switzerland. The relationships between the mixed layer and inversion layer gradients of specific humidity, and the inversion and surface fluxes of water vapor together with other turbulence parameters are investigated. The mean mixed layer gradient, ?q/?z, appears to be fairly well related to the inversion flux of water vapor, (w?q?)h, scaled with u*h or σh. The symbol u* represents the surface shear velocity, σ is a combination of u&ast and the convective velocity scale, w&ast and h the height of the mixed layer above the surface. There is also evidence that a relationship exists between the gradient in the inversion layer, (w?q?)h and an eddy diffusivity scaled as u*?h, where ?h is the thickness of the inversion layer. The atmospheric water vapor budget below the inversion, with (w?q?)h parameterized, is tested with the present data as a means of determining surface evaporation. Transport in the mixed layer appears to be more strongly affected by mechanical-type than by convective-type turbulence.