Disentangling Turbulent Gas Diffusion from Non-diffusive Transport in the Boundary Layer

Abstract An analysis based on the law of linear momentum conservation demonstrates unequivocally that mass fraction is scalar whose gradient determines gas diffusion, both molecular and turbulent. It illustrates sizeable errors in previous micrometeorological definitions turbulent flux fluctuations other scalars such as mixing ratio or density. In deference to law, we put forth a new definition for flux. Net transport then defined sum this with systematic by mean flow. This latter, non-diffusive due net upward boundary-layer momentum, Stefan flow forced evaporation, which dominant surface exchange. A comparison traditional methodology shows exact agreement between two methods regarding flux, but novelty partitioning according distinct physical mechanisms. The seen be non-negligible general, dominate under certain conditions, broad implications meteorology.