A new relation between surface flux and mean vertical concentration profiles of heavy particles in the atmospheric surface layer

The Monin-Obukhov similarity theory (MOST) is the usual framework to relate mean vertical profile and surface flux of variables in the atmospheric surface layer (ASL). It is largely used in parameterizations of mean velocity, temperature and passive scalar concentration. In this work, we propose a new relation between surface flux and mean vertical concentration profiles of heavy particles (such as dust, drifting snow, pollen grains, etc.) in the ASL. The relation includes effects of particle settling velocity and atmospheric stability, and it can be considered an extension of MOST to concentration of settling particles. The model recovers the appropriate limits when settling velocity vanishes and when the atmosphere is neutrally stratified. To assess model capabilities, a suite of Large-Eddy Simulation (LES) runs were performed including dust transport in neutral and unstable atmospheric stratification. Simulations were done for particles with diameter ranging from 1 to 30 μm and density of 2650 km/m³, corresponding to a ratio between settling velocity and friction velocity w_s/u_* varying from 0.0002 to 0.3. Application of the new model in estimating surface fluxes from mean concentration profiles obtained in field experiments are discussed. In addition, an important application of the new model is the estimation of deposition velocity, required in the parameterization of dust deposition in weather and climate models. When compared with the current model used for deposition velocity of aerosols in climate models, the velocity is as much as 23% smaller.