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:   Thursday, 16-Jul-15 10:21 CEST

Simulation models: CAMx

The Comprehensive Air quality Model with extensions (CAMx) is an Eulerian photochemical dispersion model that allows for an integrated one-atmosphere assessment of gaseous and particulate air pollution (ozone, PM-2.5, PM-10, air toxics, mercury) over many scales ranging from sub-urban to continental.

See also:

CAMx is an Eulerian (grid) photochemical dispersion model that allows for integrated "one-atmosphere" assessments of gaseous and particulate air pollution (ozone, particulate matter, air toxics) over spatial scales ranging from neighborhoods to continents. It is designed to unify all of the technical features required of "state-of-the-science" air quality models into a single open-source system that is computationally efficient, flexible, and publicly available. CAMx can be supplied environmental input fields from many meteorological models (specifically WRF, MM5, and RAMS are supported) and emission inputs developed using many emissions processors (SMOKE, CONCEPT, EPS, EMS).

Version 6.20 offers expanded capabilities over previous versions. Detailed information about all of these features is provided in the CAMx User's Guide (pdf).

In addition to the features it shares with most photochemical grid models, some of the most notable features of CAMx are:

  • Two-way grid nesting
  • Flexi-Nesting, which allows for reconfiguration of nested grids during a simulation
  • Multiple gas phase chemistry mechanism options (CB6, CB05, SAPRC99)
  • Multiple gas phase chemistry solver options (EBI, IEH, LSODE)
  • Advanced external photolysis model (TUV) with in-line cloud and aerosol adjustments
  • Two particle size treatments (modal and sectional)
  • Plume-in-Grid (PiG) module for sub-grid treatment of selected point sources
  • Multiple dry deposition options (Wesely89, Zhang03)
  • Probing Tools:
    • Ozone and Particulate Source Apportionment Technology (OSAT/PSAT)
    • Decoupled Direct Method (DDM/HDDM) for source sensitivity of ozone and other species
    • Multiple Process Analysis (PA) options
    • Reactive Tracer (RTRAC/RTCMC) Source Apportionment for air toxics
  • Mass conservative and consistent transport numerics:
    • Multiple horizontal advection solvers (PPM, Bott)
    • Multiple vertical diffusion methods (K-theory, ACM2)
  • Parallel processing using Open-MP on shared-memory systems
  • Parallel processing using Message Passing Interface (MPI) on distributed-memory systems

Data requirements for CAMx are described in:

Model output

CAMx produces gridded time-averaged concentration output files for each time step (usually hourly). The output can contains just surface layer fields or entire three-dimensional fields, both for the master grid, and a all fine grid nests together.

Basic physical processes

Module Physical Model Numerical Method
Horizontal advection/diffusion Eulerian continuity equation closed by K-theory Bott or PPM for advection explicit diffusion
Vertical transport/diffusion Eulerian continuity equation closed by K-theory Implicit advection and diffusion
Gas-Phase Chemistry Carbon Bond 6 (CB6) or SAPRC99 mechanisms ENVIRON CMC solver, IEH solver, or LSODE
Aerosol Chemistry Dry and aqueous inorganic and organic chemistry/thermo-dynamics; static 2-mode or evolving multi-section size models RADM-AQ, ISORROPIA, SOAP
Dry deposition Separate resistance models for gases and aerosols Deposition velocity as surface boundary condition for vertical diffusion
Wet deposition Separate scavenging models for gases and aerosols Uptake as a function of rainfall rate, cloud water content, gas solubility and diffusivity, PM size

Data Requirements


Supplied by a Meteorological Model

  • 3-Dimensional Gridded Fields:
    • Vertical Grid Structure
    • Horizontal Wind Components
    • Temperature
    • Pressure
    • Water Vapor
    • Vertical Diffusivity
    • Clouds/Rainfall
Air Quality

Obtained from Measured Ambient Data

  • Gridded Initial Concentrations
  • Gridded Boundary Concentrations
  • Time/space Constant Top Concentrations

Supplied by an Emissions Model

  • Elevated Point Sources
  • Combined Gridded Sources
    • Low-level Point
    • Mobile
    • Area/Non-road Mobile
    • Biogenic

Developed from Landuse/Landcover Maps, Drought Index Maps, Modeled or Satellite derived Snow Cover

  • Gridded Surface Characteristics

Derived from Satellite Measurements and Radiative Transfer Models

  • Atmospheric Radiative Properties
    • Gridded Haze Opacity Codes
    • Gridded Ozone Column Codes
    • Photolysis Rates Lookup Table

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