Intercomparison and sensitivity analysis of gas-phase dry deposition schemes

Abstract

The dry deposition of gaseous species, such as ozone, sulphur dioxide and nitrogen oxides, is a major pathway in its removal from the atmosphere. Chemical Transport Models (CTM) commonly use a resistance approach to determine the deposition velocity of these gases. The objective of this study is twofold, first to compare different dry deposition schemes used in state-of-the-art CTMs, and second to evaluate the sensitivity of such schemes to key input parameters (meteorological conditions, soil type, leaf area index, reference values for non-stomatal resistances). The canopy resistance accounts for most of the resistance in deposition velocity, therefore its formulation has been used for the intercomparison in the present study. The selected schemes are based on the formulations of Wesely (Atmos Environ 23:1293–1304, 1989), Emberson et al. (Towards a model of ozone deposition and stomatal uptake over Europe, Oslo: Det Norske Meteorologiske Institutt., 2000) or Zhang et al. (Atmos Chem Phys 3:2067–2082, 2003) with subsequent modifications accounting for the effect of phenology, photoactive radiation, vapor pressure deficit and soil–water potential. The stomatal resistance is the component of the canopy resistance related to the uptake of gases by the leaves. As it is commonly calculated for ozone and then extrapolated to other gases, the parameterization for ozone has been studied. The sensitivity analyses have been carried out by modifying the input parameters shared by most of the schemes. They are related mainly to the physiology of the vegetation and the process of gas exchange at the stomata. Meteorological inputs derived from ERA5 are used in the intercomparison. The simulated ozone deposition velocities are compared with available observational data. The dry deposition schemes show strong differences in the seasonal cycle, both in the vegetated and non-vegetated land use classes. The identification of critical parameters helps constraining dry deposition schemes incorporated in atmospheric models.