Status

As a first step towards the implementation of chemistry into WRF, "The Workshop on Modeling Chemistry in Cloud and Mesoscale Models" was held at NCAR on 6-8 March 2000  The goal of this workshop was produce  a community assessment of approaches and methodologies used for chemistry modeling in cloud and mesoscale models.

In 2002, a first version of WRF/Chem was made available as an "online" (or "inline") model.  In this form, the model is consistent, with all transport done by the meteorology model.  The same vertical and horizontal coordinates are used (no horizontal or vertical interpolation), the same physics parameterization utilized for subgrid scale transport, and no interpolation in time is performed.  This allows for easy handling from a data management standpoint, and is also the most efficient with regard to overall CPU costs.  WRF grid-scale transport of all species is conducted, with subgrid-scale transport by turbulence and convection.  Grid-scale advection in the mass coordinate WRF is mass and scalar conserving.

Presently, an improved version of WRF/Chem exists (version 3.0 released on 4 April 2008) as an "online" with an �offline� version of the model currently in development testing (see future plans). 

 

The Chemistry Package consists of the following components:

• Dry deposition, coupled with the soil/vegetation scheme.
• Aqueous phase chemistry coupled to some of the microphysics and aerosol schemes.
• Four choices for biogenic emissions:
• No biogenic emissions.
• Online calculation of biogenic emissions (as in Simpson, et al. 1995 and Guenther et al. 1994) includes emissions of isoprene, monoterpenes, and nitrogen emissions by soil.
• Online modification of user specified biogenic emissions - such as the EPA Biogenic Emissions Inventory System (BEIS) version 3.13. The user must provide the emissions data for their own domain in the proper WRF data file format.
• Online calculation of biogenic emissions using the MEGAN v2.04 biogenic emissions routine.
• Two choices for anthropogenic emissions:
• No anthropogenic emissions.
• User specified Anthropogenic emissions - such as those available from the EPA NEI-99 data inventory. The user must provide the emissions data for their own domain in the proper WRF data file format. To help a user understand the process, emissions data sets and a program is available to generate anthropogenic emissions for your domain, but care should be taken in its use as the underlying assumptions in the program might not be valid for a user's particular case.
• Two choices for gas-phase chemical reaction calculations.
• The RADM2 chemical mechanism.
• The CBM-Z mechanism.
• Several choices for gas-phase chemical reaction calculations through the use of the Kinetic Pre-Processor, or KPP. The equation files (using Rosenbrock type solvers) currently available are for:
• The RADM2 chemical mechanism.
• The RACM mechanism.
• The RACM-MIM mechanism.
• The CB4 mechanism (experimental).
• The NMHC9 mechanism (experimental).
• The SAPRC-99 mechanism.
• Three choices for Photolysis schemes:
• Madronich scheme coupled with hydrometeors, aerosols and convective parameterizations.
• Fast-J Photolysis scheme coupled with hydrometeors, aerosols and convective parameterizations.
• FTUV scheme scheme coupled with hydrometeors, aerosols and convective parameterizations.
• Several choices for aerosol schemes:
• The Modal Aerosol Dynamics Model for Europe - MADE/SORGAM
• The Model for Simulating Aerosol Interactions and Chemistry (MOSAIC - 4 or 8 bins) sectional model aerosol parameterization
• The GOCART aerosol model (experimental). aerosol parameterization
• A tracer transport option in which the chemical mechanism, deposition, etc. has been turned off. The user must provide the emissions data for their own domain in the proper WRF data file format for this option.

 

Current WRF version is 3.4.

 

Possible applications of the current modeling system:

• Prediction and simulation of weather, or regional or local climate
• Coupled weather prediction/dispersion model to simulate release and transport of constituents
• Coupled weather/dispersion/air quality model with full interaction of chemical species with prediction of O₃ and UV radiation, as well as PM

 

 

Model Evaluation

Future Plans

WRF/chem FAQs

Real-time Air Quality Forecasts from WRF/CHEM

Publications related to WRF/Chem

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