The sensitivity of modeled SO2 fluxes and profiles to stomatal and boundary layer resistances

A higher-order closure model for canopy/surface exchange is presented and applied to an oak-hickory forest to model SO₂ deposition for typical summertime conditions. The model is then used as a tool to investigate the sensitivity of modeled fluxes (the deposition velocity) and concentration profiles to the parameters used to compute the leaf boundary layer and stomatal resistances. Both the deposition velocity and concentration profiles show little sensitivity to variations in the leaf boundary-layer resistance (r _b) since it generally comprises only a small fraction of the total resistance to diffusion from the air to the sub-stomatal cavity. The deposition velocity (V _d ) is more sensitive to variations in the minimum stomatal resistance (r _s ,min) and light response coefficient (β) than r _b .It was found that 50% variations in β give a maximum difference of 0.2 cm s^?1 in V _d while 30% variations in r _s , min produce a maximum difference of near 0.3 cm s^?1.