MODELING SULFUR-DIOXIDE CONCENTRATIONS IN MT-RAINIER AREA DURING PREVENT

The MATHEW/ADPIC models (a diagnostic wind model and a particle model) which were developed at Lawrence Livermore National Laboratory, were used to compute SO2 concentrations in the Mt Rainier area during PREVE NT (Pacific Northwest Regional Visibility Experiment Using Natural Tra cers, June to September 1990). The modeled concentrations were compare d to measured concentrations at two sampling locations (Tahoma Woods a nd Paradise near Mt Rainier) which are located in a valley. The SO2 so urces considered are located along the Puget Sound (Everett, Seattle a nd Tacoma area) and south of it. New formulations were included in the models for the oxidation of SO2 and the interpolation of the wind fie ld. Because of the paucity of the meteorological data near the samplin g points, an estimation was made of the wind values in the valley, bas ed on the phenomena of wind channeling, mountain and valley winds, and historical wind observations near Mt Rainier. The models were run for several non-rainy days during the PREVENT period when large SO2 conce ntrations were observed, and for other special cases. Out of 14 days f or which the emissions of the previous night were taken into account, for 12 days the ratio of the modeled to the measured SO2 concentration s at Tahoma Woods during the daytime, was in the interval 0.45-2.00, c onsidered a good agreement. However, the agreement at Tahoma Woods dur ing the night, and at Paradise during the day and the night, were not as good. It seems that the wind Bow near Tahoma Woods under the stable conditions at night, and near the steep terrain of Paradise, were not modeled correctly, with the limited input of available meteorological observations.