Assessing New Dry Deposition Parameterization Schemes for Incorporation into Global Atmospheric Transport Models

Abstract:

Dry deposition is a key process in atmosphere-surface exchange and is an important transmission route for atmospheric gases and aerosols to enter terrestrial and aquatic ecosystems. Vertical transport of atmospheric aerosols to Earth’s surface is governed by several processes including turbulent transfer, interception, inertial impaction, settling, diffusion, turbophoresis, thermophoresis, and electrostatic effects. In global transport models (GTMs), particle dry deposition velocity (v_d) from the lowest model layer to the surface is often parameterized using an electrical resistance analogy. This resistance analogy is widely used in a modified form to compute v_d for steady-state dry deposition flux. Recently, a mass conservative formulation of dry deposition applicable to smooth and rough surfaces was proposed. Here, we evaluate dry deposition velocities computed using five different schemes with measurement results from a variety of surfaces including bare soil, grass, and coniferous, broad-leaf, and deciduous forest canopies. Based on this assessment, we provide suggestions for optimal treatment of dry deposition processes in GTMs and evaluate implementation of new dry deposition schemes.