A MULTILAYER MODEL FOR INFERRING DRY DEPOSITION USING STANDARD METEOROLOGICAL MEASUREMENTS

rn this paper, we describe the latest version of the dry deposition in ferential model, which is used to estimate the deposition velocities ( V-d) for SO2, O-3, HNO3, and particles with diameters less than 2 mu m . The dry deposition networks operated by the National Oceanic and Atm ospheric Administration (NOAA) and the Environmental Protection Agency (EPA) use this model to estimate dry deposition on a weekly basis. Th is model uses a multilayer approach, discretizing the vegetated canopy into 20 layers. The use of canopy radiative transfer and simple wind profile models allows for estimates of stomatal (r(s)) and leaf bounda ry layer (r(b)) resistances to be determined at each layer in the plan t canopy for both sunlit and shaded leaves. The effect of temperature, water stress, and vapor pressure deficits on the stomatal resistance (r(s)) have been included. Comparisons of modeled deposition velocitie s are made with extensive direct measurements performed at three diffe rent locations with different crops. The field experiment is discussed in some detail. Overall, modeled O-3 deposition velocities are in goo d agreement with measured values with the average mean bias for all su rfaces of the order of 0.01 cm/s or less. For SO2, mean biases range f rom -0.05 for corn to 0.15 cm/s for soybeans, while for HNO3, they ran ge from 0.09 for corn to 0.47 cm/s for pasture.