Density Effects on Flux Measurements

Abstract

Dry air is the media in which the turbulent diffusion of heat, water vapor, and trace gases takes place. Trace gases, such as carbon dioxide and gaseous pollutants, are passive scalars whose diffusion and transport do not alter the dynamic properties of the diffusion media. The same cannot be said of sensible heat and water vapor, which are active scalars. The sensible heat originated from the surface causes the boundary layer to become more unstable, which in turn makes the diffusion more efficient. Conversely, evaporative cooling of the surface and latent heat released by cloud condensation aloft push the boundary layer to a more stable state. These dynamic interactions are handled by the Reynolds mean conservation equations.