* O \ KWJ *1 PRO^^ Guidance on the Use of the Mesoscale Model Interface Program (MMIF) for AERMOD Applications ------- ------- EPA-454/B-23-006 October 2023 Guidance on the Use of the Mesoscale Model Interface Program (MMIF) for AERMOD Applications U.S. Environmental Protection Agency Office of Air Quality Planning and Standards Air Quality Assessment Division Research Triangle Park, North Carolina ------- Preface This document provides guidance on the use of prognostic meteorological data and the Mesoscale Model Interface Program (MMIF) in AERMOD. Included in this document are descriptions of the inputs to MMIF and recommendations on using MMIF output in AERMOD. This document is an update of the June 2022 MMIF guidance document (EPA-454/B-22-011) and reflects changes to MMIF from MMIF version 4.0 to version 4.1 and the update from AERMET 22112 to AERMET 23132 to support overwater MMIF applications with the addition of the Coupled Ocean Atmosphere Response Experiment (COARE) algorithms to AERMET proposed in the 2023 revision of the Guideline on Air Quality Models. li ------- Acknowledgements MMIF was developed by Ramboll Environ International Corporation under EPA contract number EP-D-07-102, work assignments 2-06, 4-06, 5-08, and 10-1 and EPA Contract No EP-D- 12-044, work assignment 4-07. The MMIF user's guide was developed by Bart Brashers, Chris Emery, and Prakash Karamchandani of Ramboll Environ. This guidance document was developed by the Air Quality Modeling Group of the Air Quality Assessment Division of the Office of Air Quality Planning and Standards in collaboration with representatives of EPA Regions 5, 7, and 8. in ------- Contents Preface ii Acknowledgements iii Tables v 1. Introduction 1 2. Guidance on using prognostic meteorological data for use in AERMOD 1 2.1 Number of years to model 2 2.2 Prognostic model options 2 2.2.1 Development of meteorological fields 2 2.3 Model output quality assurance 3 2.3.1 Operational evaluation 3 3. Guidance on running MMIF for AERMOD 3 3.1 MMIF Input File 4 3.2 Recommended options for selected keywords 7 3.2.1 Outputs 7 3.2.1.1 AERMET 7 3.2.1.2 AERMOD 8 3.2.2 PBL calculations 8 3.2.3 Output layers and heights 9 3.2.4 Grid cells to process 9 3.3 Surface characteristics 10 3.4 Treatment of low winds 10 3.5 Minimum mixing height and absolute value of Monin-Obukhov length 10 3.6 Overland and overwater applications 11 3.7 Post-processing of outputs 12 4. References 14 iv ------- Tables Table 1. AERMET/AERMOD keywords in MMIF input file v ------- 1. Introduction The guidance discussed in this document are recommendations for running the Mesoscale Model Interface (MMIF) program1 to generate inputs for AERMET and AERMOD. The guidance discussed in this document is an update to the June 2022 MMIF guidance (EPA-454/B-22-011). In this guidance document, when references are made to running MMIF for AERMOD, it should be inferred that this refers to AERMET as well. For regulatory applications, MMIF should be run to generate AERMET inputs as stated in section 8.4.2(a) and 8.4.5.1(b) of the final revisions to EPA's Guideline on Air Quality Models (U.S. EPA, 2017)2 and the proposed 2023 revisions to Appendix W. Regulatory applications that do not follow these sections of Appendix W will need to consult with the appropriate reviewing authority and guidelines outlined in section 3.2 of Appendix W. Given that Appendix W and specific EPA modeling guidance are often cited in relation to other non-regulatory modeling applications, such as air quality analysis and disclosure purposes under NEPA, the approach presented in this guidance document for regulatory applications also has relevance to these non-regulatory applications. While MMIF can process data for other air quality models (e.g., CALPUFF and SCICHEM), the emphasis in this guidance is for AERMOD applications conducted for regulatory purposes. This guidance document will summarize some of the inputs needed for AERMET and AERMOD MMIF processing but will refer to the MMIF User's Guide (Ramboll Environ, 2023) for more details. MMIF users are strongly encouraged to read this user's guide to obtain specific details on running MMIF 2. Guidance on using prognostic meteorological data for use in AERMOD In general, air quality modeling applications rely on the use of meteorological grid models. These models are used to more accurately simulate atmospheric processes (e.g., temperature, wind speed and direction, etc.) across a specific area. In retrospective simulations (i.e., modeling past events), the blending of observed data with computed fields yields results that are bound by ground truth. There are several meteorological grid models that can be used to develop inputs for air quality models. The most used by EPA and the modeling community is the Weather Research and Forecasting (WRF) model (Skamarock et al., 2008)3, which is supported across a broad community and provides state-of-the-science parameterizations of the atmosphere. Additionally, the Fifth Generation Penn State/NCAR Mesoscale Model (MM5) (Grell et al., 1994) can 1 http://www.epa.gov/ttn/scram/dispersion_related.htm#mmif 2 Hereafter, the Guideline will be referred to as Appendix W. 3 http://www.wrf-model.org/index.php 1 ------- generate the necessary meteorological inputs to air quality models; however, its development and maintenance is no longer supported. 2.1 Number of years to model As discussed in Section 8.4.2(e) of Appendix W (both final 2017 and proposed 2023 revisions), at least three years are required to be modeled in the prognostic model. The most recent three years are preferred, and the prognostic model domain or selected grid cells should be representative of the domain. See Section 8.4.b of Appendix W for more details about representativeness of meteorological data. 2.2 Prognostic model options 2.2.1 Development of meteorological fields For development of prognostic meteorological fields, a rigorous approach has been established within the atmospheric chemistry community. In this section, a basic guideline for recommendations on producing prognostic meteorological data will be provided. For more details related to approaches on developing modeled meteorology, please see Section 2.6 of the Modeling Guidance for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze (U.S. EPA, 2014). Dynamic meteorological models such as WRF and MM5, have myriad options available to solve for various processes within the atmosphere. Specific model options will not be provided, given that different areas of interest may respond differently under certain conditions. It is expected that the physical options chosen will be thoroughly evaluated to support their use. With regards to defining a meteorological modeling domain, it is recommended that the domain be of sufficient size and resolution to adequately capture mesoscale characteristics that impact a source location. As an example, in an area of complex, mountainous terrain, the nearest NWS observation site may not be adequately representative. In this case, the scale of meteorological model is recommended to be high enough to capture specific mountain/valley flows and be large enough to represent the upstream and other mesoscale meteorological features. Conversely, in areas where terrain and mesoscale characteristics may be more homogenous, a reasonably coarse model resolution may be applied. In addition, to avoid issues with grid boundary effects, it is recommended the modeling domains be centered over the source location. Specific case examples are provided in U.S. EPA (2018). It is also recommended that any meteorological modeling be performed using four-dimensional data assimilation (FDDA) as outlined in U.S. EPA (2014). FDDA involves providing the model with inputs related to observed and/or analyzed meteorological conditions. This technique is 2 ------- useful in improving atmospheric simulations and constraining the model from varying widely from actual observations. 2.3 Model output quality assurance 2.3.1 Operational evaluation Demonstration of the adequacy of prognostic meteorological fields can be established through appropriate diagnostic and statistical performance evaluations consistent with recommendations provided in the appropriate EPA guidance. A quantitative, statistical, and graphical analysis of the prognostic data should be completed, comparing the data to available NWS automated surface observation station (ASOS) data, as well as operational profiler data (if available), pairing both in space and time. This analysis should be completed for all years (at least three) of prognostic meteorological data to be used in the air quality simulations. Since the spatial scope of each variable could be different, representativeness should be judged for each variable separately as discussed in Section 8.4.2(b) of the final Appendix W (U.S. EPA, 2017). For example, for a variable such as wind direction, the data should ideally be collected near plume height to be adequately representative; especially for sources located in complex terrain, whereas, for a variable such as temperature, data from a station several kilometers away from the source may be adequately representative. The grid resolution of the prognostic meteorological data should also be considered and evaluated appropriately, particularly for projects involving complex terrain. Several software packages are available for use in completing this evaluation (e.g., AMET (Appel et al., 2011) and METSTAT (http://www.camx.com/download/support- software.aspx)). The adequacy of output from the meteorological models is contingent upon the concurrence with the appropriate reviewing authorities as defined in section 8.4.5.2(a) of the final Appendix W. 3. Guidance on running MMIF for AERMOD Much of the guidance presented here follows the MMIF user's guide (Ramboll Environ, 2023). Relevant information from the user's guide is summarized in this guidance for convenience but the user is strongly encouraged to read the full MMIF user's guide before attempting to run MMIF. Section 3.1 below discusses the inputs to MMIF, Section 3.2 discusses the relevant options to AERMOD and grid cells to process. Section 3.3 discusses the use of surface characteristics outside of MMIF, Sections 3.4 and 3.5 discuss the use of minimum wind speeds, mixing height and Monin-Obukhov length, Section 3.6 discusses the new features for overland and overwater processing, and Section 3.7 discusses post-processing the output from MMIF needed for input into AERMOD. 3 ------- 3.1 MMIF Input File MMIF processing is done via a control file with keywords to denote inputs, processing options, and outputs. Table 1 lists the keywords used to run MMIF for AERMET and AERMOD input only. A sample control file that illustrates all the keywords can be generated for MMIF by typing "mmif-sample" at the command prompt. See Section 4.2 of the User's Guide (Ramboll Environ, 2023) for more information. 4 ------- Table 1. AERMET/AERMOD keywords in MMIF input file. Keyword Description Syntax Start Date and time (Local Standard Time) to start processing Start YYYY MM DD HH Or Start YYYYMMDDHH Or Start YYYY-MM- DD HH:mm:ss Stop Date and time (LST) to stop processing Stop YYYY MM DD HH Or Stop YYYYMMDDHH Or Stop YYYY-MM- DD HH:mm:ss Timezone The global time zone shift from Greenwich Mean Time (GMT); Western hemisphere time zones are denoted by negative numbers Timezone HH Grid Specifies the requested output sub-grid's lower left (LL) and upper right (UR) corners; Grid corners can be specified by grid cell I, j coordinates (IJ), latitude and longitude (LL or LATLON) or MM5/WRF projected coordinate system (KM) GRID IJ iLL jLL iUR jUR Or GRID LL LatLL LonLL LatUR LatRR Or GRID KM xLL yLL xUR yUR Point Output point for AERMET, AERMOD, or AERCOARE processing. The point can be specified by grid cell I, j coordinates (IJ), latitude and longitude (LL or LATLON) or MM5/WRF projected coordinate system (KM). An optional time zone shift can also be listed1. The point keyword can be repeated for each point to be outputted. Point IJ IJ [Timezone] Or POINT LL Lat Lon [Timezone] Or POINT KM X Y [Timezone] Layers Specify the output layer structure. Layers can be aggregated (K), interpolated using layer tops (TOP), or interpolated using mid layer (MID). Layers K Layeri Layer2...LayerN Or Layers TOP Topi Top2...TopN Or Layers MID Midi Mid2.. .MidN Origin Over-ride the X,Y grid origin values found in the MM5 or WRF output file. The user specifies a latitude (LAT) and longitude (LON). Origin LAT LON C AL S CIMIXHT A value of WRF causes MMIF to pass through the PBL depth from the model with no changes. A value of MMIF causes MMIF to re-calculate PBL depths using a Bulk Richardson approach with 20 times the vertical resolution of the model data. WRF or MMIF AERMIXHT Option to specify what mixing heights to use for MMIF to AERMET processing. Options are WRF (no recalculation of mixing heights), MMIF (MMIF recalculated mixing heights) or AER MIXHT (allow AERMET to calculate mixing heights) WRF, MMIF, or AERMIXHTS AERMINMIXHT Specify the minimum allowed mixing height for AERMOD SFC output. Default is 1 m as based on AERMET AER MIN MIXHT VALUE 5 ------- Table 1. Continued Keyword Description Syntax AERMINOBUK Specify the minimum allowed absolute value of the Monin-Obukhov length for AERMOD SFC output. The default is 1 m as based on AERMET AER MIN OBUK VALUE AERMINSPEED Specify the minimum wind speed in m/s (VALUE) for AERMOD surface output file. This value should be set to 0 for both MMIF to AERMET and MMIF to AERMOD output. AER MIN SPEED VALUE FSLINTERVAL Specify the number of hours (VALUE) to write for each day to the upper air file for input into AERMET. The default value is 12 representing the 00Z and 12Z soundings. A value of 6 would write output for 00Z, 06Z, 12Z, and 18Z. A value of 1 would write output for each model hour. FSL INTERVAL VALUE AERLAYERS Specify the lowest and highest layer indices (two integers) to write to the AERMET input site-specific data and AERMOD profile file (PFL file). All layers between the two indices will be written to the file. AER LAYERS VALUE OUTPUT Specifies the outputs from MMIF for AERMET, AERCOARE, and AERMOD (MODEL keyword) and output files2. OUTPUT MODEL FORMAT FILENAME INPUT Input MM5 or WRF filename. This input is repeatable for a MMIF run. INPUT FILENAME METFORM Keyword to tell MMIF which model MM5 or WRF is being accessed. MMIF can auto-detect the model type so in general this is not needed. METFORM MM5 Or METFORM WRF CLOUDCOVER Specify the source of the cloud cover written by MMIF CLOUDCOVER ANGEVINE Or CLOUDCOVER WRF Or CLOUDCOVER RANDALL AERU SETSKC Specify if cloud cover is required output for AERMET. The default value if F and should be set to F for use with AERMET version 21112 and earlier. The value can be T for AERMET versions 22112 and later. AERU SETSKC VALUE AER_U SE_NEW Specify if outputs are for versions of AERMET 21112 or earlier (set to F) or 22112 and later (set to T). The default value is F AER_U SE_NE W VALUE 1. See Section 4.2 of the MMIF user's guide regarding the global time zone shift and point specific time zone shifts. 2. More information about the output options is discussed in Section 3.2 below. 6 ------- 3.2 Recommended options for selected keywords While most input options will be left to the discretion of the user, some recommendations on inputs are made in this guidance. One such option is the output option of MMIF, keyword OUTPUT. While MMIF can process data for input into AERMET, or AERMOD, the requirement for regulatory applications is to process the prognostic meteorological data for input into AERMET as discussed in Sections 8.4.2(a) and 8.4.5.1(b) of Appendix W, as AERMET is the meteorological pre-processor for AERMOD as discussed in those sections. The data is then processed in AERMET for input into AERMOD. Processing MMIF output through AERMET also allows the user to take advantage of some of the options in AERMET, such as the u* adjustment option. See the AERMET user's guide for details about options (U.S. EPA, 2022). For non-regulatory applications, the user may choose AERMET or AERMOD and should consult with and seek concurrence from collaborating agencies or parties involved in such modeling applications. 3.2.1 Outputs For any air quality model, the OUTPUT option is used to specify several files. While these are discussed in the MMIF user's guide in detail, they are summarized below for AERMET and subsequent input AERMOD and direct input into AERMOD as well (non-regulatory applications). 3.2.1.1 AERMET For AERMET, the first set of files is specified using the USEFUL keyword. This keyword creates a DOS batch file or Linux shell script that is used to run AERMET and the appropriate number of input files, depending on the AERMET version. For AERMET versions 21112 and earlier (AERUSENEW = F), the DOS batch file or Linux shell script that is created runs all three stages of AERMET in batch mode. It also creates the stage 1, stage 2, and stage 3 input files with the appropriate values set for the AERMET keywords such as LOCATION, XDATES, etc. For AERMET versions 22112 and later (AER USE NEW = T), the DOS batch file or Linux shell script that is created runs stage 1 and 2 in a single combined run. It also creates the combined stage 1 and 2 input file with the appropriate values set for the AERMET keywords such as LOCATION, XDATES, etc. See the AERMET user's guide (U.S. EPA, 2023a) for details on the combined stage 1 and 2 input file. Once the appropriate input stage files (stage 1, 2, and 3 for AERMET 21112 and earlier, combined stage 1 and 2 for AERMET 22112 and later) have been created, the user should check those files to ensure the correct GMT offset is used. For the upper air pathway of the stage 1 file, the LOCATION keyword should have a GMT offset corresponding to the station's location. For example, if the processed grid cell is in the Eastern time zone of the U.S. the GMT offset on the LOCATION keyword should be 5. For the surface data, the offset should be zero as that has been formatted for local time. 7 ------- The second file that is generated is specified using the keyword ONSITE. This creates a site- specific type of meteorological file that is processed via the ONSITE path in AERMET for AERMET 21112 and earlier or the PROG keyword for AERMET 22112 and later (U.S. EPA, 2022). The PROG and ONSITE pathways are largely analogous to each other. The PROG pathway was introduced with AERMET 21DRF and 22112 to allow AERMET to process MMIF output for overwater locations. This file contains 2-meter and 10-meter data and upper air data up to levels specified with the keywords MINLAYER, MAXLAYER, or LAYERS to control the number of output layers. Other data included are precipitation, surface pressure and mixing height (if requested). Beginning with MMIF version 4.0, the following are also output: cloud cover, sensible heat flux, latent heat flux, surface friction velocity (u*), hourly surface roughness (zo), potential temperature lapse rate above the mixing height, Monin-Obukhov length, and convective velocity scale (w*). Beginning with version 4.1, three additional variables, sea- surface temperature, downward longwave radiation, and sea surface temperature measurement depth are also output for overwater cells only. These variables are output in support of the overwater variable pass-through introduced with AERMET 22112 and capability in AERMET to use the Coupled Ocean Atmosphere Response Experiment (COARE) algorithms (Fairall, et al, 2003) introduced in AERMET 23132. See Section 3.6 below for more information about the overland and overwater data flag. The third keyword, FSL creates a file that mimics an upper air data file in the Forecast Systems Laboratory (FSL) format. The keyword UPPERAIR can also be used. See Section 2.2.1 of the MMIF user's guide for more details. The final keyword is AERSFC, which generates an AERSURFACE type output file with surface characteristics (albedo, Bowen ratio, and surface roughness). Note, that these are monthly surface characteristics for the period being processed. See Section 2.2.1 of the MMIF user's guide for more details. 3.2.1.2 AERMOD Three files are generated for AERMOD. The USEFUL file is a file containing the ME pathway information of the AERMOD input file, i.e., ME STARTING, SURFFILE, PROFFILE, SURFDATA, UADATA, etc. information. The SFC keyword generates the AERMOD ready surface data file and the PFL keyword generates the profile data file for input into AERMOD. 3.2.2 PBL calculations Three options are available for PBL or mixing height calculations when processing MMIF to output files for AERMET inputs via the AER MIXHT option, 1) a pass through of the WRF PBL heights (AER_MIXHT=WRF), 2) recalculation of the PBL heights using a Bulk Richardson approach (AER_MIXHT=MMIF), based on Vogelezang and Holtslag (1996) and Louis (1979) and, no PBL heights passed to the AERMET site-specific data file (AER_MIXHT=AERMET). This option uses AERMET to use its own algorithms to calculate 8 ------- mixing heights. For MMIF inputs to AERMOD, there are still two options available via the CALSCI MIXHT option (formerly the PBLrecalc option). The two options are passing the WRF mixing heights (MIXHT=WRF) or recalculation by MMIF (MIXHT=MMIF). At this time, the choice of which option to use is left to the discretion of the user as limited evaluations (U.S. EPA, 2018) have shown little difference in the three methods. Note that if a user utilizes the PBL pass through or recalculation method and wishes to use AERMET derived mixing heights later, the user can rerun MMIF or just omit the MIXHT variable and modify the read statement for the site-specific meteorological file. 3.2.3 Output layers and heights An important keyword for output is the LAYERS keyword. As shown in Table 1, the user can specify different options for the output layers from MMIF. While the choice of layers is case specific and may be dependent on the prognostic model's layer structure, two possible defaults should be adequate in most cases. The first is based on the FLM guidance and the second is a default use of MID (interpolation using layer mid-point heights) and the specification of heights corresponding to the AERMOD vertical grid. These heights are: 25, 50, 75, 100, 125, 150, 175, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, and 5000. These values have been used in past MMIF evaluations (U.S. EPA, 2018). The LAYERS keyword controls the output of the FSL formatted upper air file used by AERMET and the profile file used by AERMOD when processing MMIF to AERMOD. The AER LAYERS keyword is used to control the output of the site-specific data file read by AERMET. The AER LAYERS can be a subset of the LAYERS values. 3.2.4 Grid cells to process An AERMOD run uses surface meteorological data from one point and upper air data from one point. While MMIF can process multiple points, i.e., grid cells, the grid cell used in the AERMOD simulation should be representative of the modeling domain, following the recommendations of Section 8.4.5(b) of Appendix W. Depending on the size of the modeling domain and the grid resolution of the prognostic meteorological data, most often the representative grid cell will be the grid cell containing the facility of interest. This will often be the case for NSR/PSD types of applications. When the AERMOD modeling domain overlaps several grid cells of the prognostic meteorological data, such as for SIP demonstrations, the grid cell that is most representative of the domain should be selected following guidance on representativeness in Sections 8.4.1.b and 8.4.2.b of the final Appendix W, or it may be necessary to conduct multiple AERMOD runs for different grid cells and post-process the results to calculate the appropriate concentration metrics for the application (i.e. design values). 9 ------- 3.3 Surface characteristics MMIF will output surface characteristics, albedo, Bowen ratio, and surface roughness for input into AERMET and in the AERMOD ready surface meteorological file. When outputting data for AERMET, MMIF outputs surface characteristics for one 360° sector at monthly resolution. Beginning with MMIF 4.0, MMIF also outputs hourly surface roughness. The hourly surface roughness is used by AERMET 22112 and later for overwater applications, but the monthly value is used for overland applications. The surface characteristics are based on the land use data used by the prognostic meteorological model. These surface characteristics should be used as they are representative of the processed grid cell as discussed in Section 8.4.2(b) of the final Appendix W. 3.4 Treatment of low winds When processing MMIF for input into AERMET or AERMOD, MMIF will use the AERMINSPEED value as a wind speed threshold, for which winds below that threshold are treated as calms. This is for winds at any vertical level in the input dataset. For input to AERMET, MMIF will generate the onsite wind speed threshold option (THRESHOLD keyword) with the user supplied value (AER MIN SPEED) for the stage 1 AERMET input file. Normally, the purpose of the threshold in AERMET is to treat winds below the threshold as calm and the threshold speed is a function of the starting threshold of a site-specific anemometer. See the AERMET user's guide (U.S. EPA, 2023a) for details about this option in AERMET. When generating MMIF output for direct AERMOD input, winds below the AER MIN SPEED value will be treated as calms in the AERMOD surface file. For both MMIF to AERMET and MMIF to AERMOD, the user should set the minimum wind speed, AER MIN SPEED, to zero, since the input is prognostic data and does not have a functional minimum threshold as found in an anemometer. When processing MMIF output in AERMET, if the lowest level's wind speed is below the AERMET allowable limit (21/2 x avmin, where avmin=0.2 m/s), AERMET will reset the wind speed to the lower limit allowed in AERMET for output to the surface file. This adjustment does not take place for other levels in the WRF output file. See the AERMET user's guide for more details (U.S. EPA, 2023a). When processing MMIF output for direct input to AERMOD, no such adjustment will occur in MMIF. The wind speed from WRF is output to the AERMOD surface and profile files. 3.5 Minimum mixing height and absolute value of Monin-Obukhov length New, beginning in MMIF 3.3, is the ability to specific a minimum mixing height and minimum value of Monin-Obukov length when processing MMIF for AERMOD output. The default minimum values for each option are 1 m, as defined in Table 1 and discussed in the MMIF User's Guide (Ramboll Environ, 2023). Currently, the defaults are the recommended values for 10 ------- these options. Note, these values are not to be confused with the minimum mixing height and Monin-Obukhov length that can be specified for COARE processing (U.S. EPA, 2023a). 3.6 Overland and overwater applications Beginning with MMIF 4.0, for AERMET 22112 and later, MMIF creates a single combined stage 1 and 2 input file to AERMET. A new pathway, PROG, was added to AERMET beginning with version 22112 (U.S. EPA, 2023a). The PROG pathway is analogous to the ONSITE pathway and allows AERMET to output the data such that AERMOD knows the data are derived from MMIF. As part of the new PROG pathway, MMIF outputs an optional data type flag with the DATA keyword for the PROG data in the AERMET input file, only when processing MMIF for AERMET 22112 or later. The data file associated with the DATA keyword is the ONSITE data file described in Section 3.2.1 above. The new data flag is either "OL" for overland or "OW" for overwater. MMIF automatically determines if the requested grid cell is land based or water based and sets the flag accordingly. AERMET uses the flag to appropriately use the variables in the ONSITE (or PROG) data file. If the data are overland, then AERMET will ignore the input u*, cloud cover, Monin-Obukhov length, w*, potential temperature lapse rate, sensible and latent heat fluxes,4 and hourly z0. AERMET 22112 will process the MMIF output as done in previous versions of AERMET. Beginning with AERMET version 23132, the user has two choices in AERMET to process data that are overwater. The first option is to use the AERMET control file as it is output from MMIF and use all input variables when needed, including the hourly z0, and use the Monin-Obukhov length to determine the stability for the hour. The second option, introduced with the 2023 revisions to Appendix W (Section 8.4.6) is to use the COARE algorithms in AERMET and allow the COARE algorithms to calculate variables such as surface friction velocity and Monin- Obukhov length, among others. For guidance on the processing of prognostic data for overwater applications and COARE processing in AERMET, as well as more information about the data flag, see the AERMET User's Guide (U.S. EPA, 2023a). For an evaluation of the two options see U.S. EPA (2023b). In some applications, depending on the location and horizontal grid resolution of the prognostic data, MMIF may determine the data are overland or overwater, but the application may be best suited by the opposite designation. For example, a coastal location or location near a large inland body of water (such as the Great Lakes) may be designated as overwater when in fact, the application is best suited as treated as overland, or vice-versa. In such cases, the user can modify the AERMET input control file to change the data flag. The user should exercise best professional judgment and consult with the appropriate reviewing authority in such situations. 4 Latent heat flux is currently not used by AERMET for either overland or overwater applications. 11 ------- If the data flag is changed from "OW" to "OL", then the user should make the following changes to the AERMET input control file: 1. Change the DATA flag from OW to OL to tell AERMET the data are overland 2. In the METPREP pathway, add the keyword string METHOD STABLEBL BULKRN. This is done because AERMET will ignore the input cloud cover, Monin-Obukhov length, and u* and will use the Bulk Richardson number approach to calculate u* and Monin-Obukhov length as done with previous versions of AERMET and MMIF output. See Section 3.7.11.1 of the AERMET User's guide (U.S. EPA, 2023a) for information on the Bulk Richardson Number syntax. If the data flag is changed from "OL" to "OW", then the user only has to change the data flag from "OL" to "OW" in the AERMET control file. The user can also comment out the METHOD STABLEBL BULKRN line, but AERMET will not use the Bulk Richardson Number approach anyway since u* and Monin-Obukhov length are used or calculated by the COARE algorithms if COARE processing is invoked (see below). If the user wishes to use the COARE algorithms in AERMET with overwater data, the user should make the following changes to the AERMET input control file: 1. Add the keyword string METHOD COARE RUN COARE in the METPREP pathway. 2. For any COARE options, add the string METHOD COARE along with the options. See the AERMET user's guide for keywords and syntax 3.7 Post-processing of outputs When processing MMIF for AERMET files, a single MMIF run will produce an upper air file in the FSL format, a surface data file that will be read into AERMET as site-specific data, and surface characteristics (albedo, Bowen ratio, and surface roughness) at monthly resolution for twelve sectors. These output files will cover the period processed in MMIF. In most situations, a single MMIF run will not cover an entire three period or even a one-year period. If that is the case, the ONSITE files generated by the MMIF can be simply concatenated into a single file for the three-year period or individual yearly files before input into AERMET. The files must be concatenated in temporal order. The same can be done for the FSL files. For the surface characteristics files, when using AERMET version 22112 or later, the user can specify the surface characteristics file and appropriate years to use in the AERMET control file. See the AERMET user's guide for details. When using versions of AERMET earlier than 22112, the AERSFC files cannot be simply concatenated. For a single MMIF run, the surface characteristics are output for all twelve months and sectors. The months outside of the data processing window set by START and STOP will have missing values, while the months inside the window will have non-missing values. To create a valid AERSFC file covering the entire three-year period or desired period, an AERSURFACE file must be created with non-missing values for all months and sectors. This can be created by simply cutting and pasting the non- missing values for each month/sector combination into a single file. When creating this file, the user should make sure to incorporate the header line from one of the files into the concatenated file. This line is "** Generated by MMIF..." This line indicates to AERMET that the 12 ------- meteorological data comes from MMIF and not an observed site-specific dataset. This information is then passed to AERMOD via the surface meteorological file created by AERMET. While this does not affect the data calculations in AERMET and AERMOD, including the line ensures transparency when data files are reviewed. An alternative approach to the file concatenation steps described above, is to run AERMET for each period processed and concatenate AERMOD ready surface and profile files from the multiple AERMET runs. For the profile files, the files can be simply concatenated together, preserving the temporal order of the data (e.g., January 1, hour 1 of the first processed year is the first line and December 31, hour 24 of the last processed year is the last record of the concatenated file). For the surface files, AERMET generates a header record for each file (the record that lists the location, station identifiers, and AERMET version). When concatenating the surface files, the header record for the first concatenated file should be retained. Only the data records from the remaining surface files are needed. If the header records are retained for all files, AERMOD will not run correctly. Again, the files should be concatenated in temporal order. These steps also apply for processing AERMOD ready files when post-processing MMIF output for AERMOD. 13 ------- 4. References Appel, K.W., Gilliam, R.C., Davis, N., Zubrow, A., and Howard, S.C.: Overview of the Atmospheric Model Evaluation Tool (AMET) vl.l for evaluating meteorological and air quality models, Environ. Modell. Softw., 26, 4, 434-443, 2011. Fairall, C.W., E.F. Bradley, J.E. Hare, A.A. Grachev, and J.B. Edson, 2003: "Bulk Parameterization of Air-Sea Fluxes: Updates and Verification for the CO ARE Algorithm." J. Climate, 16, 571-591. Grell, G., J. Dudhia, and D.R. Stauffer: A description of the fifth-generation Penn State/NCAR Mesoscale Model (MM5), NCAR Tech. Note NCAR/TN-398+STR, 122 pp. Louis, J.F. 1979. "A Parametric Model of Vertical Eddy Fluxes in the Atmosphere." Journal of Atmospheric Science, 35, 187-202. Ramboll Environ, 2023: The Mesoscale Model Interface Program (MMIF) Version 4.1 User's Manual. Skamarock, W. C., Klemp, J. B., Dudhia J., Gill, D. O., Barker, D. M., Duda, M. G., Huang, X- Y., Wang, W., and Powers, J. G.: A Description of the Advanced Research WRF Version 3, National Centre of Atmospheric Research, Boulder, Colorado, 2008. U.S. EPA, 2017. Guideline on Air Quality Models. 40 CFR Part 51 Appendix W. U.S. EPA, 2018: Evaluation of Prognostic Meteorological Data in AERMOD Applications. EPA-454/R-18-002. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. U.S. EPA, 2023a: User's Guide for the AERMOD Meteorological Preprocessor (AERMET). EPA-454/B-23-005. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. U.S. EPA, 2023b: Evaluation of Prognostic Meteorological Data in AERMOD Overwater Applications. EPA-454/R-23-010. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. Vogelezang D. and A. Holtslag, 1996. "Evaluation and model impacts of alternative boundary- layer height formulations." Boundary Layer Meteor., 81, 245-26. 14 ------- United States Office of Air Quality Planning and Standards Publication No. EPA-454/B-23-006 Environmental Protection Air Quality Assessment Division October 2023 Agency Research Triangle Park, NC ------- |