||National Oceanic and Atmospheric Administration, Research Triangle Park, NC. Atmospheric Sciences Modeling Div. ;Computer Sciences Corp., Research Triangle Park, NC. Applied Technology Div.;Environmental Protection Agency, Research Triangle Park, NC. Atmospheric Research and Exposure Assessment Lab.
A diagnostic version of the RADM Engineering Model, called the Sulfate Tracking Model (STM), has been developed. Like other members of the RADM Engineering Model family (Chang et al., 1990; Binkowski, et al., 1990), the STM is a sulfur and hydrogen peroxide engineering version that makes use of chemical and oxidant (other than H2O2) fields precalculated in full RADM runs to predict atmospheric SO2, SO4(2-), and H2O2 transport, transformation, and deposition. The sulfur/H2O2 engineering models accurately reproduce RADM sulfur predictions through mathematical manipulation of the sulfur chemical dynamics, for a wide range of sulfur emissions scenarios. Hydrogen peroxide fields are calculated by making the RADM-generated OH and HO2 fields available to the STM's peroxide chemical solver, which replicates the RADM's peroxide chemical solver. Therefore, the STM dynamically tracks the influence of SO2 levels on H2O2 loss. Unique to this model is its capability of separating the complete SO4(2-) fields into constituents according to the chemical processes which created them. This permits a wide variety of diagnostic studies to be performed at low cost, aiding greatly in the authors understanding of how the RADM predicts the creation, transport, and deposition of sulfate.