Dynamic characteristics of snowfall particles in atmospheric turbulent boundary layer and its effect on dust wet deposition

Abstract. Wet deposition by snowfall refers to the scavenging of atmospheric dust by snow particles. Existing models only consider vertical scavenging in quiescent atmosphere, neglecting the complex vertical and horizontal motion of snowfall particles induced by turbulence in the actual atmosphere boundary layer, affecting the accurate estimation of wet deposition flux. However, precise quantitative analysis of dust collection mechanism during snow particle setting remains lacking under turbulence. Therefore, we employ the Euler-Lagrange numerical method to simulate and analyze snow particles dynamic characteristics and dust collection in turbulent boundary layers. It is shown that increasing friction velocity (u_*) alters the dominant factors controlling the relative motion between snow particles and air. The transition occurs at a critical dimensionless parameter α_d = V_t/κu_* = 0.2 (V_t is the terminal settling velocity of snow particles, and κ = 0.4 is the von Kármán constant). When α_d>0.2, the vertical relative motion dominates, and its dominance strengthens with increasing α_d; when α_d<0.2, the horizontal relative motion becomes predominant. This change in dynamic characteristics significantly enhances total dust collection capacity and shifts the dominant collection mechanism from vertical to horizontal: for α_d≥1, vertical collection accounts for over 75% of the total, while under horizontal dominance, its contribution exceed 50%. The results show that neglecting horizontal collection underestimates wet deposition flux. Thus, we establish a quantitative wet deposition model, providing a theoretical basis for snowfall particle collection mechanisms under turbulent, with significant applications for predicting atmospheric dust wet deposition and artificial dust removal.