CALPUFF

CALPUFF is an advanced Lagrangian puff dispersion model developed by Exponent (formerly Earth Tech). It is used for assessing the effects of air pollutant releases on air quality and visibility. The model is designated by the U.S. Environmental Protection Agency (EPA) as a preferred model for long-range transport (beyond 50 km) and for use on a case-by-case basis for near-field applications in complex terrain and coastal areas.

CALPUFF is a multi-layer, multi-species non-steady-state Gaussian puff model that simulates the effects of time- and space-varying meteorological conditions on pollutant transport, transformation, and removal. It incorporates algorithms for near-source effects, complex terrain influences, overwater transport, and wet and dry removal.

The model system consists of three main components:

• CALMET: A diagnostic 3-dimensional meteorological model that develops hourly wind and temperature fields using available meteorological observations and geophysical data. It includes a terrain processing module and options for including gridded prognostic model output.

• CALPUFF: The air dispersion model itself, which uses the meteorological fields from CALMET to simulate the advection, diffusion, and transformation of pollutants released into the atmosphere.

• CALPOST: A post-processing program that calculates concentrations and deposition fluxes from the CALPUFF output. It also provides options for visibility impact assessments.

CALPUFF is often applied in regulatory permitting processes, environmental impact assessments, and emergency response planning. It can be used to model a wide range of sources, including point sources (e.g., stacks), area sources (e.g., surface emissions), and volume sources (e.g., storage piles). The model has been extensively peer-reviewed and validated against field measurements.