2. CALPUFF
CALPUFF is an advanced, integrated Gaussian puff modeling system
for the simulation of atmospheric pollution dispersion distributed by
the Atmospheric Studies Group at TRC Solutions.
The model has been adopted by the United States Environmental
Protection Agency (EPA) in its Guideline on Air Quality Models as
a preferred model for assessing long range transport of pollutants and
their impacts on Federal Class I areas and on a case-by-case basis for
certain near-field applications involving complex meteorological
conditions.
It is maintained by the model developers and distributed by TRC.
3. The integrated modeling system consists of three main components
and a set of preprocessing and post processing programs.
The main components of the modeling system are CALMET (a
diagnostic 3-dimensional meteorological model), CALPUFF (an air
quality dispersion model), and CALPOST (a post processing package).
Each of these programs has a graphical user interface(GUI).
The CALPUFF model is designed to simulate the dispersion of
buoyant, puff or continuous point and area pollution sources as well as
the dispersion of buoyant, continuous line sources.
The model also includes algorithms for handling the effect of
downwash by nearby buildings in the path of the pollution plumes.
4. History of Calpuff
The CALPUFF model was originally developed by the Sigma Research
Corporation (SRC) in the late 1980s under contract with the California Air
Resources Board (CARB) and it was first issued in about 1990.
The Sigma Research Corporation subsequently became part of Earth Tech,
Inc. After the US EPA designated CALPUFF as a preferred model in
their Guideline on Air Quality Models, Earth Tech served as the designated
distributor of the model.
In April 2006, ownership of the model switched from Earth Tech to the
TRC Environmental Corporation, who are currently (August 2013)
responsible for maintaining and distributing the model.
5. Applications
CALPUFF is a multi-layer, multi-species non-steady-state puff dispersion
model that simulates the effects of time- and space-varying meteorological
conditions on pollution transport, transformation and removal.
CALPUFF can be applied on scales of tens to hundreds of kilometers.
It includes algorithms for subgrid scale effects (such as terrain
impingement), as well as, longer range effects (such as pollutant removal
due to wet scavenging and dry deposition, chemical transformation, and
visibility effects of particulate matter concentrations).
6. Technical Background
The model is programmed to simulate continuous puffs of pollutants
being emitted from a source into the ambient wind flow.
As the wind flow changes from hour to hour, the path each puff takes
changes to the new wind flow direction.
Puff diffusion is Gaussian and concentrations are based on the
contributions of each puff as it passes over or near a receptor point.
For these tests, CALPUFF was set to emit 99 puffs per hour(default).
A sufficiently large number of puffs is necessary to adequately
reproduce the plume solution at near-field receptors.
7. Merits
CALPUFF explicitly treats virtually all of the important physical
processes affecting transport ,diffusion, deposition, and transformation.
The three most important areas of improvement are:
a) the wind field representation provided by CALMET and the explicit
integration of mesoscale model outputs,
b) the explicit treatment of terrain effects, both in the wind-field model
and the dispersion model, and
c) a comprehensive treatment of near-field effects, including building
effects.
It provides users with a more powerful, flexible, and realistic simulation
tool.
8. Merits
It enables more in-depth outputs and analyses, especially in terms of
wind distribution (on the surface under study and at higher
elevations).
In cases of emission events or complaints (peak or stagnation periods)
Calpuff gives a more detailed output.
Better handling of low wind speed cases, stagnation, coastal, complex
terrain and flow reversals.
9. Demerits
The disadvantages of CALPUFF are primarily its increased complexity.
More data, decisions, and calculation time required.
At times, a less realistic assessment of impacts within short distances
(<50km)than that of models such as AERMOD.
