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TRAQS User Guide Page 125 9. AERMOD OPTIONS Under the TRAQS main window, press the AERMOD Options button to have access to the input data for the AERMOD air quality analysis. 9.1. AERMOD â CONTROL PATHWAY The Control Pathway tab of the AERMOD Options window contains the following options: AERMOD Options - Control Pathway tab
TRAQS User Guide Page 126 Options Under this section, the following options are available: ï¬ Title: Specify here a description for your TRAQS AERMOD project (optional). ï¬ FASTALL Run Option (Non-Regulatory Option): This option reduces AERMOD model run times. FASTALL is a non-default AERMOD option and therefore it is recommended that you check with your regulatory body to see if this option can be used for your analysis. Re- sults obtained using the DEFAULT options against the ones obtained by the use of the FAST- ALL option have shown a slight overprediction of about 1.02%. Review the "Addendum- Userâs Guide for the AMS/EPA Regulatory Model â AERMOD" (U.S. EPA 2011a) for more infor- mation. ï¬ CO 1-Hour to 8-Hour Persistence Factor (default = 0.7): The Carbon Monoxide (CO) NAAQS consists of both 1-hour and 8-hour standards. The 1992 CO Guideline recommends a default persistence factor of 0.7 to convert peak 1-hour predicted concentrations to peak 8- hour estimations. Averaging Period (Not Available for Selection on the Interface) Averaging periods will be automatically setup for you depending of the NAAQS pollutant being model. See table below for supported pollutants, averaging periods, and high values: Pollutant Averaging Periods CO 1-HR and 8-HR (2nd HIGH) PM2.5 24-HR (8TH HIGH) ANNUAL PM10 24-HR (6TH HIGH)
TRAQS User Guide Page 127 Dispersion Options In this section, you should specify if your modeling site is in an Urban or Rural setting. Urban Dispersion Options ï¬ Population: This is the population for the urban area that will influence the heat island ef- fect calculated by AERMOD. ï¬ Urban Area Name (Optional): Specify the name of the urban area or leave it blank. The default value of 1.0 meters is used by TRAQS and the AERMOD model for the ur- ban roughness length. For more information on how to properly specify the Urban Population, see Section 5.2 of the US EPA AERMOD Implementation Guide. Flagpole Receptors AERMOD output results are, by default, calculated at ground level. However, the user can specify at which height concentrations should be calculated by using the Flagpole Receptors option. ï¬ No: Select this option if you want concentrations to be calculated at ground level. ï¬ Yes: Select this option if you want concentrations calculated at a certain height. Specify the height (in meters) or accept the default of 1.8 m. 9.1.1. URBAN AND RURAL DISPERSION COEFFICIENTS The project can be classified as urban or rural, in which the selection of either urban or rural disper- sion coefficients should be based upon either the Land Use Procedure or Population Density Procedure: ï¬ Land Use Procedure: Circumscribe a 3 km radius circle, Ao, about the source using the mete- orological land use typing scheme - o If land use types including industrial, commercial and residential account for 50% or more of Ao, select the Urban option, o Otherwise use the Rural option.
TRAQS User Guide Page 128 ï¬ Population Density Procedure: Compute the average population density, p, per square kilo- meter with Ao as defined above - o If p > 750 people/km2, select the Urban option, o If p <= 750 people/km2, select the Rural option. Of the two methods above, the Land Use Procedure is considered a more definitive criterion. The Population Density Procedure should be used with caution and should not be applied to highly industrialized areas where the population density may be low and thus a rural classification would be indicated, but the area is sufficiently built-up so that the urban land use criteria would be satis- fied. In this case, the classification should already be urban and urban dispersion parameters should be used. 9.2. AERMOD â METEOROLOGY PATHWAY The Meteorology tab of the AERMOD Options window contains the following options: AERMOD Options - Meteorology Pathway tab
TRAQS User Guide Page 129 Meteorological Data Files If you selected "PM Project-Level Conformity Analysis" as the Analysis Type, then representa- tive meteorological data, preprocessed by the US EPA AERMET program, for the most recent five consecutive years should be used. Under this section, you must specify the following: ï¬ Surface Met File (SFC): The surface met data file contains hourly observed and calculated surface variables. ï¬ Profile Met File (PFL): The profile met data file contains the observations made at each level of an on-site tower, or the one level observation taken from National Weather Service data. The Surface and Profile meteorological data files used by the AERMOD model must be generated using the US EPA AERMET meteorological preprocessor. For more infor- mation on AERMET, visit https://www3.epa.gov/ttn/scram/metobsdata_procac- cprogs.htm#aermet. Press this button to remove the specified file. Press this button to preview the specified file in a text editor. Press this button to specify the requested file. If you selected "CO Project-Level Analysis (Screening)" as the Analysis Type, then the two meteorological data files to be specified (Surface and Profile) must be generated by the US EPA MAKEMET program. The MAKEMET program generates a site-specific matrix of screening meteor- ological conditions based on user inputs. For more information on MAKEMET, visit https://www3.epa.gov/ttn/scram/disper- sion_screening.htm#aerscreen For more information on MAKEMET parameters for CO screening analysis, see MAKEMET Screening Meteorology.
TRAQS User Guide Page 130 Anemometer Base Elevation (MSL) ï¬ Base Elevation (m): Specify here the base elevation, in meters, above mean sea-level (MSL) of the surface station's primary meteorological tower. Read Entire Met File? In this section, you specify whether you want the model to read the entire meteorological files or only a sub-set of it, by choosing one of the following options: ï¬ Yes: This is the default option and requests the AERMOD model to use the entire period from the specified met data files. ï¬ No: This option allows you to specify a subset of the met data files by specifying the day, month, year and hour of the first and last record to be read from the meteorological data files. Any records in the data files that occur before the Start Date and after the End Date are ignored. ï¬ Start/End Date & Hour: If you selected the No option, then these fields become enabled. Place the cursor on the year, month, or day and click on the arrows to increase or decrease the date. 9.2.1. MAKEMET SCREENING METEOROLOGY The table below shows an example of MAKEMET parameters selected when generating the screen- ing meteorological data based on worst case inputs. The values below are only suggestions. Check with your regulatory body for final approval on these parameters. Parameter Urban Rural Anemometer Height (m) 10.0 10.0 Minimum and Maximum Ambient Temperature (K) 250, 250 250, 250 Minimum Wind Speed (m/s) 0.5 0.5 Adjust Friction Velocity (U*)? Yes Yes Wind Direction (deg from North) 10 to 360 deg in 10 deg incre- ments 10 to 360 deg in 10 deg increments Albedo (Wintertime) 0.35 0.35
TRAQS User Guide Page 131 Parameter Urban Rural Bowen Ratio (Bo) - Average Wintertime 1.5 1.5 Surface Roughness Length, Zo (m) 1.0 0.5 Wind Speed (m/s) 1.0 1.0 Obukhov Length (m) 483.5 (D) 163.3 (E) Mixing Height (m) 276 122 Source: CO Screening Analysis Using AERMOD, Michael Claggett, FHWA Resource Center, TRB Workshop 9.3. AERMOD â SOURCE PATHWAY The Source Pathway tab of the AERMOD Options window contains the following options: AERMOD Options - Source Pathway tab
TRAQS User Guide Page 132 Source Pathway Options Source Parameters File: This file contains the information for all the road links and off-network links specified under the Map & Links module. These links are converted into the proper AERMOD source type and an input file is generated which includes the AERMOD keywords and parameters which fully describe the links and off-network links. ï¬ Road Links: These are converted into AERMOD LINE sources. ï¬ Off-Network Links: These are converted into AERMOD AREAPOLY sources. The image below shows an example of the Source Parameters file. Functionality of Buttons Press this button to preview the file in a text editor. Press this button to re-generate the Source Parameters file.
TRAQS User Guide Page 133 9.4. AERMOD â RECEPTOR PATHWAY The Receptor Pathway tab of the AERMOD Options window contains the following options: Discrete Receptors Under the Discrete Receptors tab you will be able to specify and/or view discrete receptor loca- tions to be included in the AERMOD modeling runs. Discrete Receptors information are displayed in a grid. Discrete Receptors can be specified in several ways as described below: 1. Importing: You can import discrete receptors from a CSV file. Use the Export button to gen- erate a template that you can use for entering your data in the proper format. 2. Converting: You can specify a Cartesian Grid and convert into Discrete Receptors. This option is available under the Grid Receptors tab. 3. Drawing: You can graphically specify individual receptor grid points on the map area by using the tool. 4. Generating: You can use the Generate Link Receptors utility to generate a series of discrete receptors along Road Links based on user-defined settings for setback distances away from the road and spacing between receptor locations. AERMOD Options - Receptor Pathway tab
TRAQS User Guide Page 134 5. Specifying: You can manually specify discrete receptors by pressing the Add button and enter- ing X and Y coordinates directly into the grid. Displays the Generate Link Receptors dialog allowing you to specify set- tings for generating a series of discrete receptors along road links. Deletes any discrete receptors within specified exclusion zones. Exports the contents of the Discrete Receptor grid to a CSV file. The exported file can serve as a template that you can edit before re-importing into TRAQS again. Allows you to import discrete receptors from a CSV file. Before using this feature, make sure you have the proper CSV file format by using the Export button first. Adds a new row to the Discrete Receptor grid allowing you to enter the X and Y co- ordinates for a new receptor. Deletes any selected discrete receptors from the Discrete Receptor grid. You can use the Shift key or Ctrl+ Alt keys to select multiple grid rows. Deletes all discrete receptors from the Discrete Receptor grid. Receptor Pathway Tab - Discrete Receptors
TRAQS User Guide Page 135 Grid Receptors Under the Grid Receptors tab you will be able to specify a Uniform Cartesian grid by specifying the following parameters: ï¬ Center Coordinates (m): X and Y coordinates, in meters, for the center of the grid. ï¬ Grid Spacing (m): Grid spacing in the X and Y directions. ï¬ No. of Receptors: Number of receptors (grid nodes) in X and Y directions. ï¬ Dimension (m): Auto-calculated fields that display the total length of the grid in X and Y direc- tions. Grid Receptors are written to the AERMOD Input File as a Uniform Cartesian Grid us- ing the GRIDCART UCART keyword. Press this button to automatically generate a grid covering your entire modeling do- main. A default spacing of 50 meters is used for the X and Y directions, however, you can specify your own values. Press this button to clear all fields and remove the grid from your project. Press this button to convert the grid into discrete receptors allowing you to de- lete receptors that are within exclusion zones. Converting a Receptor Grid into Discrete Receptors allows you to remove discrete re- ceptors that you do not want to include in your modeling analysis.
TRAQS User Guide Page 136 Additional Receptor Options You will be able to specify an external receptor pathway file using the option below. ï¬ Include Receptors from External File: This option allows you to specify an external receptor file to be included in the AERMOD input files. If this option is selected, the Specify File field becomes enabled. The user is then able to press the Load button and specify the file. The Receptor File (*.rou) must be in the format accepted by the US EPA AERMOD model (see Receptor File Format). The external receptor file is specified under the AERMOD input file using the INCLUDED keyword option.
TRAQS User Guide Page 137 9.5. RECEPTOR FILE FORMAT TRAQS allows you to specify an external Receptor Pathway file (*.rou), generated by another program, to be included in the AERMOD input files. The format of the receptor file must follow specifications provided under Section 3.4 of the "Userâs Guide for the AMS/EPA Regulatory Model â AERMOD" (U.S. EPA 2004a). The RE STARTING and RE FINISHED keywords CANNOT be included in the external file. Example of a Receptor Pathway External File