About

Description

SCIPUFF is an atmospheric dispersion model with a wide range of application.  The turbulent diffusion parameterization is based on second-order turbulence closure theory, which relates the dispersion rate to velocity fluctuation statistics.  In addition to the average concentration value, the closure model provides a prediction of the statistical variance in the concentration field resulting from the random fluctuations in the wind field.  The variance is used to estimate a probability distribution for the predicted value.

SCIPUFF uses a collection of Gaussian puffs to represent an arbitrary three-dimensional, time-dependent concentration field, and incorporates an efficient scheme for splitting and merging puffs.  Wind shear effects are accurately modeled, and puffs are split when they grow too large for single point meteorology to be representative.  These techniques allow the puff model to describe complex flow effects on dispersion, such as terrain-driven circulations.

SCIPUFF has been developed with a flexible interface, to describe many types of source geometry and material properties.  The model also uses several types of meteorological input, including surface and upper air observations or three-dimensional grid data.  Planetary boundary layer turbulence is represented explicitly in terms of surface heat flux and shear stress using parameterized profile shapes.

The principal enhancements to Version 2.8 (Sykes et al., 2014) are the capability to assimilate meteorological observations into numerical weather prediction fields and an improved secondary evaporation model that accounts for a range of droplet sizes on the surface.

History

SCIPUFF was initially developed for modeling power plant plumes[1] with funding from Electric Power Research Institute. The model was incorporated as the core transport and dispersion model for DoD’s HPAC model in 1995. SCIPUFF was approved as an alternative model for Appendix W by EPA in 1998. Over the years, numerous enhancements have been made to the model, such as the inclusion of gas phase, aqueous phase and aerosol chemistry for SCICHEM, using mesoscale meteorology fields in native coordinates, reading WRF output files directly and source estimation using an adjoint model. The model is capable of transporting gases, liquid and particles and includes dynamic effects associated with buoyant and dense gases. It can be used for a variety of release types such as instantaneous, continuous, moving, jet, stack or point sources. Some of the other models that use SCIPUFF as the transport and dispersion model or sub-grid model are Joint Effects Model (JEM), Maritime Security Risk Analysis (MSRAM), CMAQ-APT and CHIMERE Plume-in-Grid model.

SCIPUFF has been extensively used and validated for various short range (up to 50 km) and long range (up to 3000 km) dispersion studies over the years. Some of the long range experiments that were studied using the SCIPUFF model are Across North America Tracer Experiment (ANATEX) study[2], European Tracer Experiment (ETEX) study[3] and Cross Appalachian Tracer Experiment (CAPTEX) study[4].

References
[1] Sykes, R.I., W.S. Lewellen and S.F. Parker. 1985. A Gaussian Plume Model of Atmospheric Dispersion Based on Second-Order Closure, J. Climate and Appl. Met, 25, 322-331
[2] Sykes, R.I., S.F. Parker, and D.S. Henn. 1993. Numerical Simulation of ANATEX Tracer Data Using a Turbulent Closure Model for Long-Range Dispersion, J. Appl. Met, 32, 929-947
[3] Mosca, S., G. Graziani, W. Klug, R. Bellasio and R. Bianconi (1997), “ATMES-II – Evaluation of long-range disperions models using 1st ETEX release data: Volume 1”, JRC-Environment Institute.
[4] Lee Jared A., L. Joel Peltier, Sue Ellen Haupt, John C. Wyngaard, David R. Stauffer, and Aijun Deng, 2009: Improving SCIPUFF Dispersion Forecasts with NWP Ensembles. J. Appl. Meteor. Climatol., 48, 2305–2319