The dry deposition of particles to a forest canopy: A comparison of model and experimental results

This paper evaluates estimates of the dry deposition velocity (vd) for acidifying aerosol and particles with base cations based on the model by Slinn (1982, Atmospheric Environment, 16, 1785–1794) with experimental results from experiments in the Speulder forest (The Netherlands). Results point at two dominating driving forces for particle deposition: particle size and friction velocity. Model results obtained show largely similar relations to the measurements. On average for the Speulder forest, we obtained a vd for sulphate of 1.3 ± 1.2 cm s−1 during daytime and 1.0 ± 1.4 cm s−1 during nighttime. These values are about 2–3 times larger than for other inference methods available in the literature, however, they are in line with recent observations. For base cations we estimated an average vd of 5.1 ± 3.9 cm s−1. Based on model results we propose a simplified parametrisation of vd for sulphate, nitrate, ammonium and base cation aerosol, which can be used to calculate the dry deposition of the compounds to forests on a grid scale for deposition maps. The simplified parametrisation compares favourably with the more detailed model calculations.