United States Environmental Protection Agency Atmospheric Sciences Research Laboratory Research Triangle Park NC 27711 Research and Development EPA/600/S8-87/046 Dec. 1987 Project Summary User's Guide for RAM- Second Edition Joseph A. Catalano, D. Bruce Turner, and Joan H. Novak RAM is an air quality model based on the Gaussian-plume simplification of the diffusion equation which assumes time independence in the input meteorology and concentration. The model is primarily used to deter- mine short-term (one hour to one day) concentrations from point and area sources. A maximum of 250 point sources and 100 area sources can be considereed to yield pollutant concen- trations at a maximum of 180 recep- tors. The simulation is done using hourly meteorological data for periods ranging from one hour to one year. A default option is available in the model for regulatory applications. Use of this option automatically sets certain parameters to preassigned values for consistency with the ' 'Guideline on Air Quality Models (Revised)" (EPA, 1986). This Project Summary was devel- oped by EPA's Atmospheric Sciences Research Laboratory. Research Trian- gle Park, NC. to announce key findings of the research project that is fully documented in a separate report of the same title (see Project Report ordering information at back). The RAM algorithm is a Gaussian- plume dispersion model that calculates short-term pollutant concentrations from multiple point and/or area sources at a user-specified receptor grid in level or gently rolling terrain. Pollutants consi- dered are relatively non-reactive, such as sulfur dioxide and suspended particu- lates. Both urban and rural situations can be simulated. In the rural mode, the model uses the Pasquill-Gifford disper- sion parameters; in the urban mode. those proposed by Briggs based on the work of Pooler-McElroy are used. Plume rise is calculated following the methods of Briggs and both buoyancy rise and momentum rise are included. For point sources, concentrations are determined using distance crosswind and distance upwind from the receptor to each source. For area sources, the narrow plume simplification of Gifford and Hanna is used with the modification that the area sources are not at ground level, but have an effective height. Inputs to the model are a set of options selected by the user, source parameters, meteorological data, and receptor infor- mation. Using the hourly meteorology, concentrations are calculated for recep- tor locations either specified by the user or generated by the program. Emissions and source parameters for point or area sources are required inputs. The meteo- rological data base, and hence the simulation, can vary from one hour to one year. Concentrations for 5 averaging periods can be computed. For long-term runs such as a year, a high-five tabu- lation can be obtained to determine the highest and second highest concentra- tions at each receptor for each of five averaging periods. Receptors can be specified by the user or they can be generated by the program. If they are input by the user, receptor name as well as coordinates may be provided on input. For model execution, the user specifies parameters and options needed for the application. Requried parameters are type of pollutant, number of sources, averaging periods), power-law wind- profile exponents, and whether the urban or rural mode is to be used. Options are included for the treatment of stack-tip ------- downwash, gradual plume rise, and buoyancy-induced dispersion. The user also specifies types of sources and those that are significant, receptor configura- tion, characteristics of emission sources, and meteorological inputs. Whether the run is part of a segmented run, outputs desired, and use of the default feature are also specified by the user. The default feature sets parameters and options for regulatory application; final plume rise and momentum plume rise are used as are buoyancy-induced dispersion and stack-tip downwash. Calm wind condi- tions are treated following the "Calms Processor (CALMPRO) User's Guide." Both point and area sources are considered by the model. Their particu- lars can be included in the run stream or they can be read from disk or tape files. Source coordinates and parameters must be given, as well as emisison rates. A total of 250 point sources and 100 area sources are permitted. Of these, up to 25 point sources and 10 area sources can be labeled significant to obtain their contribution at a receptor separately. As with the data on emissions, the meteorology can be read as part of the input stream, from a file processed by the program RAMMET, or from a file having the format of RAMMET. Surface parameters and mixing height must be present for each simulation hour; the meteorological file is of a variable length from one hour to one year. Receptors can be specified by the user or they can be generated by the model. If they are input by the user, receptor name as well as coordinates may be provided. If generated by the program, the user selects whether a polar coor- dinate grid of 180 receptors (36 radials by 5 distances) or a honeycomb receptor configuration is desired. Also, when significant sources are specified, the model selects two receptors downwind of each source where maxima are likely to occur. A total of 180 receptors are permitted. On output, the model produces printed and disk or tape files. The printed output lists the options and source information including a ranking according to source height; those selected by the user as significant are properly identified. Recep- tors are next listed with their appropriate coordinates. This is followed by the meteorological parameters as input by the user. Model-calculated concentra- tions are tabulated by receptor. Various other output files can be obtained. Joseph Catalano is with Aerocomp, Inc.. Costa Mesa, CA 92626; the EPA authors Bruce Turner (also the EPA Project Officer, see below) and Joan Novak are with the Atmospheric Sciences Research Laboratory, Research Triangle Park, NC 27711. The complete report, entitled "User's Guide for RAM—Second Edition," fOrder No. PB 88-113 261/AS; Cost: $25.95. subject to change) will be available only from: _^ National Technical Information Service ', '- 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Atmospheric Sciences Research Laboratory U.S. Environmental Protection Agency Research Triangle Park. NC27711 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 Official Business Penalty for Private Use $300 EPA/600/S8-87/046 ------- |