air quality assessment & management
Reference and User Manual
AirWare   On-line Reference Manual
  Release Level 7.0
  Revision Level beta
  Release Date 2015 03

Last modified on:   Saturday, 5-Dec-15 11:08 CET

CAMx sub-domains, nesting:

CAMx incorporates two-way grid nesting (up to four levels), which means that pollutant concentration information propagates into and out of all grid nests during model integration. Any number of grid nests can be specified in a single run, where horizontal grid spacing can vary from one grid nest to another (note that vertical grid structures must be consistent among all grids).
CAMc User Guide V6-20, p 67ff

From the CAMx scenario page, the button "Domain" leads to a description and editor of the current domain/subdomain structure. Domains can be added (selected from the model domain OBJECT CLASS) or deleted, and their resolution set, subject to the rules listed below; for any violations of the nesting rules, and appropriate error message is shown:

The following rules and constraints apply:

  1. The ratio of master grid cell size to nested grid cell size must be an integer (e.g., a “meshing factor” of 3 means that 3 nested cells span the distance of 1 master cell, resulting in an area of 9 nested cells per master cell);
  2. For telescoping grids (a nested grid containing an even finer grid), the cell size of the finest grid must be a common denominator for all parent grids above it (e.g., a 36-12-4 km or 36-12-2 km arrangement is allowed, but a 36-12-9 km is not);
  3. The restriction in (2) above does not apply to parallel nested grids of the same generation (e.g., 4 km and 5 km grids can be located in different areas of a master grid provided that the master cell size is some multiple of 20 km);
  4. Nested grids cannot overlap, although they may share a common lateral boundary or edge;
  5. Nested grids cannot extend into a lateral boundary, or non-modeled, area of the master grid;
  6. CAMx is currently configured to allow four “generations” of nests (e.g., four levels of telescoping grids); this can be extended in the code if more than four levels of nests are required;
  7. The total vertical depth of each nested grid must exactly match the depth of the master grid, and nested grid vertical layer structures must be consistent with the master grid in terms of the number of layers and their thicknesses;

CAMc User Guide V6-20, p 68ff

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