8.6 A Mass Consistency Method for Air Quality Modeling over Complex Terrain

摘要

The adjustment of vertical winds helps achieve mass conservation in AQMs. It yields better ozone performance when applied with more accurate vertical advection schemes such as Bott's. However, since those schemes are non-linear, an iterative solution is needed. This introduces small mass conservation errors. Recall that the mass was strictly conserved with the first-order upwind scheme. Both methods introduce trajectory deviations compared to wind fields generated by meteorological models. Therefore we developed a third method which mixes the use of vertical winds adjustment with concentration renormalization under strong vertical wind shear conditions. Recall that renormalization is not mass conservative therefore some mass conservation errors are introduced but the trajectory deviations are smaller than those seen in pure vertical wind adjustment methods.