AN INVESTIGATION OF THE ADOM DRY DEPOSITION MODULE USING SUMMERTIME O3 MEASUREMENTS ABOVE A DECIDUOUS FOREST

The dry deposition module in the Acid Deposition and Oxidant Model (ADOM) has been isolated from the complete model to accept local meteorological measurements in order to provide local estimates of dry deposition velocities. These are compared with observed O3 data obtained during the summer of 1988 over a deciduous forest. The comparison shows that the model systematically overpredicts by about 70% the dry deposition velocity for two selected days and for the average diurnal variations, obtained from the entire observed time series for July and August of 1988. The canopy resistance, to transfer of O3, is the major contributor to the model's total resistance for O3. In addition to the possible errors due to the "Big Leaf" approximation, sensitivity studies show that key parameters for reducing the systematic bias in the model are the Leaf Area Index, as well as mesophyll, stomatal, ground and cuticle resistances. For dry deposition velocities of SO2, the model also shows sensitivity to these parameters as well as the canopy wetness. A brief discussion on some mathematical approximations in the model is provided.