BREEZE Software and Data / Trinity Consultants

BREEZE Met Data Facilitates Long Range Dispersion Modeling


Courtesy of Courtesy of BREEZE Software and Data / Trinity Consultants

U.S. EPA requires that facilities located within 200 km of Class I areas or others with visibility degradation issues conduct long-range dispersion modeling studies. CALPUFF, an EPA-approved model for long-range transport modeling, is a non-Gaussian, non-steady state, puff model that operates in a Lagrangian framework, unlike the Eulerian approach used by Gaussian dispersion models. The extensive hourly meteorological data, or met data, required for this approach makes a CALPUFF modeling analysis more sophisticated than ISCST3 or even AERMOD modeling. Preparation of the CALPUFF-ready met data file requires the use of the CALMET preprocessing system. Populating the CALMET system with met data and generating the necessary information can take as long or longer than an entire modeling project using the currently approved short-range dispersion models. A typical modeling domain can encompass many meteorological stations, and each additional station increases the amount of time required to process the data. Trinity's BREEZE software group has extensive experience processing data for use with the ISC, AERMOD, and ADMS dispersion modeling systems. These data are produced in accordance with EPA guidelines for filling missing observations and other quality assurance procedures. BREEZE software staff can provide the amalgam of met data that CALMET requires, including surface data, upper air sounding data, precipitation data, gridded terrain and land use data, and prognostic model output data used to generate a 3-D wind field over the entire modeling domain. In scenarios involving facilities located near a body of water, CALMET also processes buoy data to account for the ambient air/sea temperature differential. Trinity has a wealth of experience in generating all of these sophisticated files. The BREEZE meteorological data group already has a substantial database of surface and upper air files and can obtain the remaining data within the timeframe of the project. The importance of having access to met data becomes more evident as the dispersion modeling community seeks ways to improve the accuracy of models while preserving the conservative approach necessitated by environmental regulations. Theoretical improvements in these models are taking place in the meteorological algorithms, which places a premium on fully understanding the atmosphere, as CALMET requires modelers to make assumptions about what processes to include. CALPUFF modeling analyses are a significant undertaking, and the BREEZE meteorological data group has the ability to help facilitate that process.

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