Varying Partitioning of Surface Turbulent Fluxes Regulates Temperature‐Humidity Dissimilarity in the Convective Atmospheric Boundary Layer

Abstract

AbstractExperimental evidence shows that temperature‐humidity () similarity in the atmospheric surface layer (ASL) is reduced as Bowen ratio () increases over land. However, underlying physical mechanisms remain not well understood. With large‐eddy simulations, dissimilarity is investigated in the steady‐state, convective boundary layer (CBL) over homogeneous landscape with varying . As increases from 0.4 to 2.0, the entrainment ratio for slightly decreases but that for q largely increases. As a result, local production of humidity variance is substantially enhanced in the upper CBL and transported to the lower CBL by vigorous large eddies, contributing significantly to nonlocal fraction. However, the increased temperature variance in the ASL associated with strong heat flux is larger than that transported from the upper CBL. Such asymmetry in vertical diffusion induced by varying partitioning of surface fluxes strongly regulates dissimilarity even under perfect conditions valid for Monin‐Obukhov similarity theory.