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Boundary Conditions

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barronh edited this page Aug 31, 2017 · 2 revisions

Create Boundary Conditions for CMAQ

Limited area chemical transport model use boundary conditions from global models. The boundary condition file has data around the perimeter of the model domain. There are four conceptual steps to create boundary conditions from a global model:

  • Horizontal interpolation
  • Vertical interpolation
  • Metadata addition
  • Chemical translation

The most difficult by far is Chemical translation. The pncglobal2cmaq.py script attempts to make the other three easy, so that we can focus our energy on the last. The example below produces a boundary condition file for CMAQ from a GEOS-Chem ND49 output.

$ ls
METBDY3D_20160101 bc_profile_CB05.dat mappings.json ts20160101.bpch
$ pncglobal2cmaq.py --METBDY3D METBDY3D_20160101 --BCONPROFILEPATH=bc_profile_CB05.dat --mapping=mappings.json ts20160101.bpch
NO2, NO, O3, ...
$ ls
METBDY3D_20160101 bc_profile_CB05.dat mappings.json ts20160101.bpch ts20160101.bpch.BCON.nc
  • pncglobal2cmaq.py is a script included with PseudoNetCDF
  • METBDY3D_20160101 file is a CMAQ input boundary meteorology file
  • bc_profile_CB05.dat is a static profile input to CMAQ's BCON
  • mappings.json is described on its own page
  • ts20160101.bpch is a ND49 output from GEOS-Chem

In addition to the ND49 diagnostic, boundary conditions can be produce from other GEOS-Chem files and from other models. For example:

  • GEOS-Chem ND49 (e.g., ts20160101.bpch)
  • GEOS-Chem trac_avg (e.g., trac_avg.bpch)
  • RAQMS (*.nc)

The mappings.json file has all the necessary information for chemical and vertical coordinate definition. More details can be found about downloading or creating your own mappings.json.

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