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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