Guidance on the Use of the Mesoscale Model 

Interface Program (MMIF) for AERMOD 

Applications

EPA-454/B-15-001

July 2015

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

Air Quality Modeling Group

Research Triangle Park, North Carolina
ii

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.
iii

Acknowledgements

MMIF was developed by Environ International Corporation under EPA contract number EP-D07-102, work assignments 2-06, 4-06, 5-08, and 10-1. The MMIF user’s guide was developed 

by Bart Brashers and Chris Emery of 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.
iv

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 ............................................................................................ 2

2.3.1 Operational evaluation................................................................................................... 2

3. Guidance on running MMIF for AERMOD ............................................................................... 3

3.1 MMIF Input File ................................................................................................................... 3

3.2 Recommended options for selected keywords...................................................................... 6

3.2.1 Outputs........................................................................................................................... 6

3.2.1.1 AERMET................................................................................................................ 6

3.2.1.2 AERMOD ............................................................................................................... 7

3.2.2 Output layers and heights............................................................................................... 7

3.2.3 Grid cells to process....................................................................................................... 7

3.3 Surface characteristics .......................................................................................................... 7

3.4 Treatment of low winds........................................................................................................ 8

3.5 Post-processing of outputs.................................................................................................... 8

4. References................................................................................................................................. 10
v

Tables

Table 1. AERMET/AERMOD keywords in MMIF input file........................................................4
1

1. Introduction

The guidance discussed in this document are recommendations for running the Mesoscale Model 

Interface (MMIF) program1to generate inputs for AERMET and AERMOD. 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 proposed revisions to EPA’s 

Guideline on Air Quality Models (U.S. EPA, 2015)2. 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 (Environ, 2014) 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 commonly 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., 

 

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
2

1994) is capable of generating 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 the proposed Appendix W, at least three consecutive 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 the proposed Appendix W for more details about representativeness of 

meteorological data.

2.2 Prognostic model options

2.2.1 Development of meteorological fields

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) recommends approaches for developing 

prognostic meteorological data. While specific recommendations for model options are not 

provided, this guidance discusses the proper steps to ensure the data are representative of the air 

quality model domain. The reader is referred to U.S. EPA (2014) for details on the development 

of the meteorological fields.

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 proposed Appendix W (U.S. EPA, 2015a). 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 considered to be adequately representative. The grid resolution of the prognostic 
3

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 proposed Appendix W.

3. Guidance on running MMIF for AERMOD

Much of the guidance presented here follows the MMIF user’s guide (Environ, 2014). 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 and Section 3.4 discusses post-processing the output from MMIF needed for input into 

AERMOD.

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. 

A sample control file that illustrates all of the keywords can be generated for MMIF by typing 

“mmif –sample” at the command prompt. See Section 4.2 of the User’s Guide (Environ, 2014) 

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-MMDD_HH:mm:ss

Stop Date and time (LST) to stop processing Stop YYYY MM DD HH

Or

Stop YYYYMMDDHH

Or

Stop YYYY-MMDD_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 I J [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 Layer1

Layer2...LayerN

Or

Layers TOP Top1 Top2...TopN

Or

Layers MID Mid1 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

PBL_recalc A value of FALSE (default value) causes MMIF to 

pass through the PBL depth from the model with no 

changes. A value of TRUE causes MMIF to recalculate PBL depths using a Bulk Richardson 

approach with 20 times the vertical resolution of the 

model data.

PBL_recalc FALSE

Or

PBL_recalc TRUE

AER_MIN_SPEED Specify the minimum wind speed in m/s (VALUE) 

for AERMOD surface output file.

AER_MIN_SPEED VALUE

FSL_INTERVAL 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
5

Table 1. Continued

Keyword Description Syntax

AER_LAYERS 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

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 are 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 the proposed 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 and addendum for details 

about options (U.S. EPA, 2004; U.S. EPA, 2015b). 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 particular 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 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. Once the stage 1, 2, 

and 3 input files 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 timezone 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.

The second file that is generated is specified using the keyword ONSITE. This creates a sitespecific type meteorological file that is processed via the ONSITE keyword in AERMET (U.S. 

EPA, 2014). This file contains 2-meter and 10-meter data and upper air data up to levels 

specified with the keywords MIN_LAYER, MAX_LAYER, or LAYERS to control the number 

of output layers.

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.
7

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 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, a default use of MID

(interpolation using layer mid-point heights) and the specification of heights corresponding to the 

AERMOD vertical grid heights should be adequate in most cases. 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, 2015c).

3.2.3 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 proposed Appendix W.

3.3 Surface characteristics

MMIF will output surface characteristics, albedo, Bowen ratio, and surface roughness for input 

into AERMET and also in the AERMOD ready surface meteorological file. When outputting 

data for AERMET, MMIF outputs surface characteristics for one 360o sector at monthly 
8

resolution. The surface characteristics are based on the landuse 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 proposed Appendix W. 

3.4 Treatment of low winds

When processing MMIF for input into AERMET, MMIF will generate the onsite wind speed 

threshold option (THRESHOLD keyword) with a value of 0.5 m/s for the stage 1 AERMET 

input file. The model user has the option to include this option when running AERMET. See the 

AERMET user’s guide and addendum (U.S. EPA, 2004; U.S. EPA, 2015b) for details about 

AERMET this option. When generating MMIF output for direct AERMOD input, winds below 

0.5 m/s are treated as calms in the AERMOD surface file.

3.5 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. If using the MMIF 

surface characteristics files, 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 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 
9

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.
10

4. References

Appel, K.W., Gilliam, R.C., Davis, N., Zubrow, A., and Howard, S.C.: Overview of the 

Atmospheric Model Evaluation Tool (AMET) v1.1 for evaluating meteorological and air 

quality models, Environ. Modell. Softw., 26, 4, 434-443, 2011.

Environ, 2014: The Mesoscale Model Interface Program (MMIF) Version 3.1 User’s Manual.

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.

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, 2004: User’s Guide for the AERMOD Meteorological Preprocessor (AERMET). 

EPA-454/B-03-002. U.S. Environmental Protection Agency, Research Triangle Park, 

NC 27711.

U.S. EPA, 2015a. Guideline on Air Quality Models. 40 CFR Part 51 Appendix W.

U.S. EPA, 2015b: Addendum - User’s Guide for the AERMOD Meteorological Preprocessor 

(AERMET). EPA-454/B-03-002. U.S. Environmental Protection Agency, Research 

Triangle Park, NC 27711.

U.S. EPA, 2015c: Evaluation of Prognostic Meteorological Data in AERMOD Applications. 

EPA-454/R-15-004. U.S. Environmental Protection Agency, Research Triangle Park, NC 

27711.

United States

Environmental Protection

Agency

Office of Air Quality Planning and Standards

Air Quality Assessment Division

Research Triangle Park, NC

Publication No. EPA-454/R-15-004

July 2015