Eulerian Grid Models

Most AQMs are based on one set of mass-conservation equations that can mathematically describe the formation, transmission, and fate of pollutants in the atmosphere. The equation, also called governing equation, usually include emission, meteorology, transportation, deposition, transformation, and chemical reaction processes. The governing equation is usually established with Eulerian approach (fixed coordinate for space), it is also called the Eulerian Grid Model. Unfortunately, this equation is too difficult to solve analytically. Instead, it is usually solved numerically, and by dividing the real-world atmosphere into smaller meshes or grids (including horizontal and vertical grids). By assuming the physical and chemical properties in each grid are homogeneous, the governing equation could be solved numerically for each grid. In this way, the distribution of air pollutant could be obtained within the calculation domain. The Eulerian grid models are usually solved directly with less assumption, therefore a lot of data and information in each grid, including pollutant emissions, meteorology, terrain, land use, solar radiation, and so on, are also necessary to conduct the simulation. The demand for computer resources is much greater than other types of AQMs.

Large Eulerian Grid Models are usually designed and developed to simulate the “real” atmosphere. Therefore, most applications are regional and urban scale air quality issues, including:

• Quantitative assessment of the air pollution control strategies on the effectiveness in improving air quality.
• Quantitative impact assessment of various emission sources on air quality.
• Cause analysis of fine suspended particles (PM_2.5)and Ozone(O₃)Pollution.
• Evaluation on the long-range trans-boundary and regional transport of pollutants.
• Estimation of the allowable emissions (holding capacity) required for total air pollution control planning.
• Quantitative evaluation of domestic cross-zone air pollution interaction.
• Quantitative impact assessment of the large pollution sources on air quality.
• Other applications: such as air quality monitoring station site selection, representative evaluation of air quality monitoring station sites, air quality forecasting system, air quality real-time early-warning system, emission estimation data evaluation, etc.