A new parameterization of particle dry deposition over rough surfaces

Abstract

Abstract. In existing particle dry deposition schemes, the effects of gravity and surface roughness elements on particle motion are often poorly represented. In this study, we propose a new scheme to overcome such deficiencies. Particle deposition velocity is a function of aerodynamic, surfacecollection and gravitational resistances. In this study, the effect of gravitation settling is treated analytically. More importantly, the new scheme takes into consideration the impacts of roughness elements on turbulent particle diffusion and surface particle collection. A relationship between aerodynamic and surface-collection processes is established by using an analogy between drag partition and depositionflux partition. The scheme is then tested against a windtunnel data set for four different surfaces and a good agreement between the scheme predictions and the observations is found. The sensitivity of the scheme to the input parameters is tested. Important factors which affect particle deposition in different particle size ranges are identified. The scheme shows good capacity for modeling particle deposition over rough surfaces.

Evaluation of five dry particle deposition parameterizations for incorporation into atmospheric transport models

“…where C B and n B are empirical parameter functions of flow regimes and are given by Zhang and Shao (2014).…”

“…2.5 Zhang and Shao (2014) (ZS14) scheme Zhang and Shao (2014) used an analytical solution of the steady-state flux equation to derive an expression to compute dry deposition velocity V d as…”

“…The gravitational resistance term R g is calculated as R g = 1/V g . The parameterization of the surface resistance term R s is given by Zhang and Shao (2014) as follows:…”

“…The largest discrepancy was observed for particle sizes of 0.3 to approximately 5.0 µm. Studies also suggest that in many dry deposition parameterizations, the largest uncertainty exists for 0.1-1.0 µm particles because of the differing treatments of some key particle deposition processes such as Brownian diffusion (Van Aalst, 1986;Petroff and Zhang, 2010;Zhang and Shao, 2014).…”

“…In the present study, five dry deposition parameterizations, developed by Zhang et al (2001), Petroff and Zhang (2010), Kouznetsov and Sofiev (2012), Zhang and He (2014), and Zhang and Shao (2014), are selected for an intercomparison of performance in terms of accuracy, uncertainty, and sensitivity. Throughout this paper, these models are referred to as Z01, PZ10, KS12, ZH14, and ZS14, respectively.…”