Dynamically consistent formulations in meteorological and air quality models for multiscale atmospheric studies. Part II: Mass conservation issues

Eulerian air quality models that require gridded meteorological inputs have to adapt to recent advances in meteorological models for fully compressible atmosphere. When the input meteorological data are recast with a robust fully compressible governing set of equations, chemistry-transport models can follow the dynamic and thermodynamic descriptions of the meteorological data closely. For evaluating mass consistency in meteorological data, one may take advantage of the characteristics of the governing set of equations applicable for a specific vertical coordinate system. This paper discusses how the data from meteorological models should be used in air quality simulations. It proposes a general methodology to conserve mass of trace species in air quality models by maintaining consistency in the wind and air density fields. Limitations of several simplifying assumptions on atmospheric dynamics are also discussed. In summary, it attempts to bridge the information gap between dynamic meteorologists and air quality modelers by highlighting the implication of using different meteorological coordinates and dynamic assumptions for air quality simulations.