An Analytical Dispersion Model for Sources in the Atmospheric Surface Layer with Dry Deposition to the Ground Surface

Abstract

ABSTRACTThis study presents a dispersion model based on an analytical solution of two-dimensional advection-diffusion equation to simulate the crosswind integrated concentration in the bounded atmospheric boundary layer. The dispersion model considers the power law profiles of wind speed and vertical eddy diffusion coefficient and deposition velocity at the ground surface. A closed form analytical solution of the advection-diffusion equation for these parameterizations of wind and eddy diffusivity was derived by considering the deposition through lower boundary condition at the ground surface. A sensitivity analysis of the dispersion model for ground level concentrations with varying deposition velocities at the ground surface was performed. Hanford diffusion experiment for a depositing tracer was used to evaluate the dispersion model in stable condition. Model was evaluated by accounting both deposition and non-deposition at the ground surface. The simulated concentrations from the proposed dispersion model with dry deposition are in good agreement with those observed and the model predicts ~72% cases within a factor of two. It was shown that the consideration of no-deposition condition in the model for a depositing tracer gives rise to a larger over-prediction to the observations in comparison to with deposition.