CALPUFF- Air Quality modelling
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CALPUFF is an atmospheric pollution dispersion model developed in the late 1980s and adopted by the EPA for assessing long-range pollutant transport impacts. It consists of CALMET, a diagnostic meteorological model, CALPUFF, the air quality dispersion model, and CALPOST, a post-processing package. CALPUFF simulates the dispersion of point, area, and line sources over tens to hundreds of kilometers, accounting for effects like building downwash and pollutant removal processes. While more complex than some other models, it provides a powerful and flexible tool through its explicit treatment of important physical processes and integration of mesoscale meteorological data.
CALPUFF- Air Quality modelling
- 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.
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