# Presentation: 692173

## FAA EDMS Airport Air Quality Model Development

- Ted Thrasher
- EDMS Project Manager
- September 23, 2005

## Introduction

- Required Model
- Aviation Sources
- Aircraft
- APUs (Auxiliary Power Units)
- GSE (Ground Support Equipment)
- Non-aviation Sources
- Power Plants, Fuel Tanks
- Roadways, Parking Facilities

**Notes:**
The Emissions and Dispersion Modeling System (EDMS) is required by the Federal Aviation Administration (FAA) for air quality analysis involving aviation sources which include aircraft, auxiliary power units (APU) and ground support equipment (GSE)[i].  EDMS also offers the capability to model other airport emission sources that are not aviation-specific, such as power plants, fuel storage tanks and ground access vehicles.  As its name implies, EDMS can be used to model both emissions as well as atmospheric dispersion. [i].	Federal Aviation Administration, Office of Environment and Energy.  Emissions and Dispersion Modeling System (EDMS) User’s Manual.  FAA-AEE-04-02 (Revision 1), October 2004.

## History

- 1985

- 2005

- 1985

- Complex Source Microcomputer Model

- 1991
- EDMS

- 1993
- EPA Preferred Guideline Model

- 1997
- Re-Engineered as EDMS 3.0

**Current Version**
**EDMS 4.3**

- 1998
- FAA Required Model for Aviation Sources

- 2001
- EDMS 4.0
- First release with AERMOD

- 2000
- EDMS 3.2Last EPA Modeling Conference

- 2002
- EDMS 4.1

- 1990

- 1995

- 2000

**Notes:**
EDMS was originally developed in the mid-1980s as a complex source model capable of assessing air quality impacts due to airport development and accepted as an Environmental Protection Agency (USEPA) “Preferred Guideline” model in 1993.  In 1997, it was completely re-engineered to meet both scientific and policy related needs, and benefit from data and methodology advances.  In 1998, the FAA elevated the status of EDMS to a required model when conducting air quality analysis for aviation sources.  This was done to ensure consistency and quality in aviation-related air quality analyses. The aviation emission algorithms and data used in EDMS are well established and are USEPA developed and/or recommended.
The current major release of EDMS, version 4.3, includes substantial enhancements over the 2002 version 4.1 release.

## Emissions Inventories

- Data Sources
- ICAO Databank
- MOBILE
- NONROAD
- AP-42
- User Input Requirements
- Aircraft fleet ops, taxi/queue times, etc...
- Traffic levels, parking lot throughput
- Stationary Source operations

**Notes:**
EDMS includes emission factors for various types of airport sources.  For example, it incorporates all aircraft engine emissions data contained in the International Civil Aviation Organization (ICAO) Engine Exhaust Emissions Data Bank[i], which makes up over two-thirds of EDMS’s aircraft engine emissions data.  The remaining third of EDMS’s aircraft engine emission data originate from U.S. military reports, shared manufacturer data and USEPA documents.[ii],[iii]  EDMS also includes USEPA’s on-road models: PART5[iv], MOBILE5a, MOBILE5b[v] and MOBILE6.2[vi].  Version 4.2 marked the second phase of migration towards USEPA’s draft NONROAD[vii] model for GSE, incorporating April 2002 and May 2004 draft NONROAD derived emission factors.
EDMS can be used to create an emissions inventory for any individual airport emission source or combination of emission sources.  To create an aircraft emissions inventory, the modeler inputs the aircraft fleet present at an airport and the annual number of landing and takeoff (LTO) cycles for each aircraft.  The modeler can specify each aircraft’s taxi and queue time, as well as the takeoff weight and approach glide slope angle, which are used to determine the takeoff, climb out and approach time in mode (TIM) values.  The takeoff, climb out, and approach TIM values in EDMS’s internal database originate from methodology presented in the Society of Automotive Engineers (SAE) Aerospace Information Report (AIR) 1845 and account for aircraft-engine specific performance.  Similar to aircraft, the modeler has the ability to define and include the adjunct APU and GSE activity, roadway traffic, parking lot throughput, and stationary source and training fire operations.

## Dispersion Analyses

- User Input Airport Layout
- Gates, Taxiways, Queues, Runways, etc...
- AERMOD
- AERMIC (AMS/EPA)
- AERMET
- Historical Meteorological Data Processor
- AERMAP
- Terrain Preprocessor

**Notes:**
For dispersion analyses, EDMS generates input files to be processed by USEPA’s AERMOD[i], which has been bundled with EDMS since version 4.0.  The manner in which AERMOD is employed in EDMS is based on guidance from the American Meteorological Society/USEPA Regulatory Model Improvement Committee (AERMIC), which is responsible for developing AERMOD and introducing state-of-the-art modeling concepts into USEPA local-scale air quality models.
AERMOD can be run from within EDMS, however the user may choose to run AERMOD external to EDMS with the generated input files.  Because AERMOD requires both surface and upper air meteorological data, AERMET is also bundled with EDMS.  AERMET is AERMOD’s meteorological preprocessor which transforms many different formats of “raw” weather data into an “AERMOD-ready” format.  Similar to AERMOD, AERMET can be run either internally or externally to EDMS.  EDMS also includes an interface to AERMAP, the terrain preprocessor for AERMOD.  Once the dispersion analysis is initiated within EDMS, the execution and control of AERMET, AERMAP and AERMOD is entirely transparent to the user.
[i].	Cimorelli, Alan J., et al.  AERMOD: Description of Model Formulation (Version 02222).  EPA454/R-02-002d, October 2002.

## Recent Developments

- Expanded Pollutant Reporting
- Database Repair
- Aircraft Times in Mode
- GSE Modeling Enhancements
- Direct interface to MOBILE 5a, 5b and 6.2
- Parking Facility Modeling
- Roadway and Taxiway Modeling
- Stationary Source Modeling
- Dispersion Modeling Enhancements

**Notes:**
After nearly two years in development, EDMS 4.2/4.3 includes significant enhancements such as: expanded pollutant reporting; database “repair”; additional taxi time options; interfaces to MOBILE versions 5a, 5b and 6; enhanced GSE modeling; new interfaces to AERMET, AERMOD and AERMAP; enhanced stationary source modeling capability; and enhanced parking structure modeling.

## Expands the list {CO, THC, NOx, SOx, PM10} to include {VOC, NMHC, PM2.5} 

Users specify the reporting units of their choice: 
metric tons / short tons
kilograms / pounds
Smaller units provide a better level of resolution to users with smaller studies
Metric units provide greater utility to international users

- Users specify the reporting units of their choice:
- metric tons / short tons
- kilograms / pounds
- Smaller units provide a better level of resolution to users with smaller studies
- Metric units provide greater utility to international users

- Expanded Pollutant Reporting

**Notes:**
The pollutants modeled by EDMS 4.1 consisted exclusively of CO, THC, NOx, SOx and PM10.  EDMS 4.2 expands the number of considered pollutants from five to eight with the addition of VOC, NMHC and PM2.5.  This is accomplished by the incorporation of a new data table of conversion factors which are used to compute VOC and NMHC from THC values to and PM2.5 from PM10 values based on the type of emissions source.
Moreover, EDMS 4.1 always reported emission inventory totals in units of short tons (2,000 pounds avoirdupois).  In EDMS 4.2, users can specify the reporting unit of their choice: metric or short tons, kilograms or pounds.  The introduction of smaller units provides a better level of resolution to users with smaller studies, and the broadening use of metric units provides greater utility to international users.

## Database Repair

- EDMS detects data file corruption upon opening a study
- The data can usually be recovered because system crashes usually only affect the file header and NOT the data

**Notes:**
In the past, EDMS database corruption could result from a power outage or system crash while the model was running.  When EDMS 4.2 detects that a data table is corrupted, it prompts the user for permission to attempt repair on the affected file.  A repair can be completely within seconds because it is most often a simple matter of correcting the file header to match the file contents.  The user is immediately alerted as to whether or not a requested repair was successful. 

## Aircraft Times in Mode

- Methodologies
- USEPA/ICAO definitions
- SAE AIR 1845 Performance based
- EDMS 3 used the USEPA/ICAO definitions exclusively
- EDMS 4.0 & 4.1 used the performance based exclusively
- EDMS 4.2 and 4.3 provide users with a choice
- EDMS 4.2 and 4.3 include default taxi times from ASPM historical data

**Notes:**
EDMS 4.2/4.3 allows users to apply USEPA/ICAO default times in mode to the built-in system aircraft.  These USEPA/ICAO default times in mode were used in EDMS versions prior to 4.0, but were eliminated in lieu of performance based default times in mode in versions 4.0 and 4.1.  Users can toggle between using the USEPA/ICAO and performance based times in mode, in EDMS 4.2’s Study Setup window; however, the EDMS default is the performance based times in mode.  The EDMS default times should be used for all FAA analyses unless prior authorization is obtained from FAA (e.g., for use of USEPA/ICAO default times in mode).
EDMS 4.2 /4.3includes default taxi times for a limited number of airports and calendar years based on available Aviation System Performance Metrics (ASPM) historical data from the FAA’s Office of Policy and Plans.  When airport-specific data is not available, the default taxi time defaults to the USEPA/ICAO taxi time of 26 minutes.  In EDMS 4.2’s Study Setup window, users can also specify their own default taxi time.  Regardless of their source, default taxi times can be overridden by the user for any particular aircraft in a study.

## GSE Modeling Enhancements

- Deterioration Factors
- Draft NONROAD 2004 deterioration factors based on year of manufacture
- Fleet averages from the draft 2002 NONROAD used when the age is not specified or data is unavailable
- Studies with custom GSE assignments can easily revert to the default assignments

**Notes:**
The EDMS migration toward NONROAD now incorporates deterioration factors.  Modeling equipment deterioration increases the accuracy with which an aging GSE population or unit is modeled.  As engines age, they naturally function less efficiently and their emission rates increase.  EDMS continues to include a default age distribution, which the user can override to better reflect the scenario.
From the exhaustive database of non-road vehicles and equipment in the April 2002 draft NONROAD model, EDMS 4.1 incorporated fleet average emission factors (in grams of pollutant per hour per horsepower) provided by USEPA to FAA as applicable to aircraft GSE for four fuel types: gasoline, diesel, CNG and LPG.  EDMS 4.2 retains this dataset, supplementing it with a new data table based on the database of the 2004 draft of NONROAD to increase model accuracy.  When a user specifies the age or year of manufacture for a particular GSE unit or population, the emission factors are based on the 2004 draft data.  When a default age distribution is specified, the earlier 2002 dataset is applied.  This methodology is employed for both GSE populations and GSE assigned to aircraft, and both interfaces (i.e., the Aircraft Operations & Assignments and GSE Population windows) have been enhanced to allow for the additional specifications.
The 2004 draft NONROAD model determines emission factors from the kind of fuel burned, engine technology and equipment deterioration.  Technology is phased in according to the year of operation.  The user must specify fuel.  If the age or year of manufacture is also specified by the user, EDMS 4.2 assumes the most common technology in use during the year of manufacture.  In the event of a tie, to be conservative, the older technology is assumed.  Fuel, rated horsepower and technology determine the zero-hour emission factors and deterioration coefficients. 
Users can continue to modify the default parameter values to best characterize a study airport.
Now, restoring an aircraft’s default GSE assignments in EDMS 4.2 is a simple matter of checking a box in the Aircraft Operations & Assignments window.  

## MOBILE 5a, 5b and 6.2

- As with aircraft TIM, user’s are given a model choice
- Static lookup table replaced with bundled models which dynamically compute emission factors
- MOBILE6.2 allows users to specify vehicle type
- Applies to both Parking Facilities and Roadways

**Notes:**
EDMS 4.1 employed a static lookup table of emission factors for on-road vehicles whose values were compiled from multiple runs of USEPA’s MOBILE5a and PART5 models using default parameters.  EDMS 4.2 comes bundled with the actual on-road models (i.e., PART5, MOBILE5a, MOBILE5b and MOBILE6.2) to provide users with a choice in the applied on-road model, and increased flexibility and accuracy in modeling vehicular emission factors.  Users select the model version to use with a drop-down menu in the EDMS 4.2 Study Setup window.  Use of the USEPA on-road models in EDMS makes the large cumbersome static lookup table obsolete.
The lookup table of version 4.1 provided default on-road emission factors as a function of calendar year, altitude (above or below 5000 feet), annual ambient temperature and speed.  In EDMS 4.2, users opting for MOBILE6.2 can additionally specify vehicle type (e.g., passenger car, truck, bus, etc...), fuel and year of manufacture.  The specification of these additional parameters implies improved accuracy in the results.  Both the parking lot and roadway interfaces of EDMS 4.2 have been enhanced to allow for the specification of the new parameters. 

## Parking Facility Modeling

- Users can model multi-level parking garages
- Users specify:
- number of levels
- vertical spacing between levels
- EDMS uses vertically stacked AERMOD area sources

**Notes:**
EDMS 4.2 allows users to model multi-level parking garages with vertically stacked AERMOD area sources.  Previous versions were only capable of modeling single-level parking lots.  In the enhanced parking lot interface, users can specify the number of levels and the vertical spacing between levels.  The ease with which this is accomplished greatly aids user productivity.

## Roadways & Taxiways

- EDMS 4.0 and 4.1 hard-coded the widths of all roadways and taxiways at 20 meters
- In EDMS 4.2 and 4.3, users can specify the width of roadways and taxiways
- The ability to override the default width provides the users with improved dispersion modeling accuracy

**Notes:**
EDMS 4.0 and 4.1 hard-coded the widths of all roadways and taxiways at 20 meters.  EDMS 4.2 allows users to specify the width of roadways and taxiways, and the respective interfaces have been enhanced accordingly.  The ability to override the default width provides the users with improved dispersion modeling accuracy.

## Stationary Sources

- Consistency with *Air Quality Procedures for Civilian Airports and Air Force Bases* (The Air Quality Handbook) for all 9 categories:
- Boiler/Space Heaters
- Emergency Generators
- Incinerators
- Aircraft Engine Testing
- Fuel Tanks
- Surface Coating/Painting
- Deicing Areas
- Solvent Degreasers
- Sand/Salt Piles
- AERMOD source type specified by the user:
- POINT, VOLUME or AREA

**Notes:**
EDMS 4.2 introduces a transition from how stationary sources are modeled and provides increased accuracy and flexibility for users.  Previously, EDMS made assumptions regarding stationary sources that were intended to simplify the data requirements and reduce the overall burden on the analyst conducting a less rigorous analysis of stationary sources; refined stationary source analysis is intended to be conducted using stationary source-specific dispersion models.  However, this left the EDMS methodology inconsistent with the guidance contained in the Air Quality Procedures for Civilian Airports and Air Force Bases (also known as The Air Quality Handbook[i]).  EDMS 4.2 resolves these inconsistencies, while maintaining an ease of use for the novice or less rigorous analyses through the use of default values.
Users can model any of the nine source types described in The Air Quality Handbook: Boiler/Space Heater, Emergency Generator, Incinerator, Aircraft Engine Testing, Fuel Tank, Surface Coating/Painting, Deicing Area, Solvent Degreaser and Sand/Salt Pile.  The new interface employs a dynamic parameter list such that each stationary source type includes the same parameters required in the Air Quality Handbook.  For example, the parameters for boilers and space heaters include the fuel sulfur and ash content, which are used to adjust the emission factors.  For combustion source types, it is possible to account for the effects of installed pollution control equipment.  In previous versions, users had to enter their own emission factors to achieve the same results.  Incidentally, version 4.2 also allows users to edit the emission factors of training fires which was not previously possible.
In addition to the new emissions parameters, source representation for dispersion has also changed.  For any stationary source, users can select the most appropriate model (i.e., point, volume or area) and specify the required parameter values and the base elevation.  The increased user flexibility increases accuracy in dispersion modeling.

## Dispersion Enhancements

- AERMOD build 02222 with:
- PRIME plume rise
- Building downwash
- New AERMOD wizard

**Notes:**
EDMS 4.2 includes the most recent version of AERMOD (build 02222) which incorporates PRIME (Plume RIse Model Enhancements), a building downwash algorithm for point sources developed by the Electric Power Research Institute (EPRI).
The use of downwash algorithms in PRIME are generally preferred since they have been shown to be more accurate than the Schulman-Scire algorithms[i] used in the early versions of AERMOD that were bundled with EDMS 4.0 and 4.1.
EDMS 4.2 makes use of the PRIME algorithms by providing users with a new building definition interface. 
The AERMOD input file generator window has been redesigned into a multi-page wizard in EDMS 4.2 to provide users with maximum flexibility in generating AERMOD input files.
The previous interface implementation only provided the minimum parameters necessary in AREMOD input file generation.
The new interface also delivers an increased ease of use.  For example, users can use the interface to create input files for processing multiple averaging periods simultaneously.  
Additionally, users can also specify AERMAP extracted terrain data files to be included.
A greater number of source group definitions have also been created to allow for “chi over Q”  post-processing.
The last page of the new wizard allows users make full use of AERMOD’s reporting capabilities.

## Dispersion Enhancements

- New user interface for buildings

**Notes:**
Users define buildings in the Buildings window by providing a polygonal footprint, base elevation and height.  EDMS includes the defined buildings in the generated AERMOD input files by computing the set of direction-specific parameters (e.g., projected width and depth) required by PRIME for each point source.  Including the effect of buildings on dispersion from point sources improves the accuracy of point source dispersion modeling.  

## Dispersion Enhancements

- Improved AERMET wizard with met station data
- AERMAP user interface

**Notes:**
The AERMET wizard has been overhauled in EDMS 4.2 to provide users with automatic file format detection and improved error reporting.  A data table of weather stations is included to automatically provide the user with the latitude-longitude positions from which the weather observations were made.  The enhancements reduce the burden of manual input on the user and assist the user in detecting errors in the file processing as early as possible.  Users are able to override any of the automatically supplied inputs to provide flexibility.  
To incorporate terrain effects, EDMS 4.2 includes AERMAP, AERMOD’s terrain pre-processor.  Previous versions of EDMS assumed flat terrain.  The use of AERMAP requires more data and analysis for the user; however because its use is optional, incorporation of this feature does not necessarily place additional burdens on the user.  Much of the topological data required by AERMAP can be obtained free of charge.  EDMS 4.2 makes use of AERMAP by providing users with an AERMAP interface which can be used to run the preprocessor.  Users can specify multiple US Geological Survey (USGS) Digital Elevation Model (DEM) data files and their domain of interest.  EDMS runs AERMAP which extracts from the data files the terrain elevations for all of the sources and receptors in the study as well as the hill scales for the receptors.  The generated source and receptor files can be later included in an AERMOD run.  Including the effect of terrain on dispersion has a significant impact on concentrations and greatly improves the accuracy of the dispersion modeling in EDMS.

## Aircraft PM First Order Approximation

- Provides a conservative estimate of aircraft PM emissions
- Uses smoke number from ICAO Databank
- Only applies to commercial jet engines
- Serves an interim purpose of meeting PM compliance issues now, while the science and accuracy of PM measurement techniques mature

*Emission Rate**Mass of PM **= 2.4 (Smoke Number)**1.8** Fuel Flow*

## Future Developments

- AERC Analyses
- Multiple scenarios
- Multiple years
- Dynamic Flight Profiles
- SAE AIR 1845 methodology
- BADA data & methodology
- Boeing Fuel Flow Method 2
- Climate & Meteorology
- Modified thrust settings

**Notes:**
AERC analyses require examination of airport operations over several years under two or more scenarios (e.g., baseline and proposed, or build and no build).  EDMS 4.2 can model only one year of airport operations under one scenario at a time.  The next major release of EDMS (version 5.0) will be capable of modeling a range of years under multiple scenarios, thereby increasing flexibility by providing users with the power to create single EDMS studies for submission under the VALE program.
To enhance EDMS modeling accuracy and increase consistency between the Integrated Noise Model (INM) and EDMS, the two tools will refer to a common algorithm based on SAE AIR 1845 methodology.  Previously, aircraft flight profiles were stored statically as points in a data table that was based on default assumptions and nominal conditions.  With a shared algorithm, aircraft performance and flight paths will be modeled identically in both the INM and EDMS.  The dynamic aspect of the algorithm allows aircraft to be modeled under various meteorological and operating conditions, improving model accuracy.  For example, reduced takeoff thrust (85% power) at 0oC could be modeled.

## Future Developments

- Improved aircraft taxi path definition
- Define inbound/outbound paths
- Use standard taxiway names
- Taxiway assignment obsolete
- Enhanced roadway/taxiway modeling
- Multiple points
- Curves
- Connected segments
- Roadway directionality

**Notes:**
In addition to defining an airport’s taxiway layout, users will be able to define outbound and inbound pathways for every gate-runway pair, as necessary.  EDMS would automatically determine the pathway to be followed based on an aircraft’s gate and runway assignments; and therefore, taxiway assignment would be unnecessary.  This reduction of input requirements is expected to increase user productivity.
EDMS 5.0 will allow users to define roadways as a series of segments rather than just two endpoints.  This feature will reduce the redundant endpoint input for connected and curved roadways, and served to increase user productivity.  The overlap of the representative area sources of connected segments would vanish, increasing model accuracy.  Moreover, users will be able to specify roadway directionality (i.e., one-way or two), thereby increasing flexibility. 

## EDMS Design Review Group

- 12 experts representing
- Government (FAA and EPA)
- Academia
- Industry
- Recommend model enhancements
- Provide technical guidance for model application
- Review changes to the model
- Meetings are held as required with frequent interaction between meetings

## Aviation Environmental Design Tool (AEDT)

- Assess interdependencies between aviation-related noise and emissions
- Incorporating today’s tools:
- EDMS
- SAGE
- INM
- MAGENTA
- In development from 2005 through 2010

## CONCLUSIONS

- These enhancements have
- Improved accuracy
- User flexibility
- FAA
- Researching to better understand aviation emissions
- Improving EDMS modeling capability
- Developments planned in the near future are intended to
- Further refine the fidelity
- Increase user flexibility
- Expand the capabilities of EDMS

**Notes:**
In 2004, the FAA released EDMS 4.2 which incorporated many significant enhancements including: interfaces to MOBILE versions 5a, 5b and 6.2; enhanced GSE modeling; new interfaces to AERMET, AERMOD and AERMAP; an enhanced stationary source modeling capability and several other new features.  These enhancements have improved the accuracy of the tool and user flexibility.  FAA is continuously conducting research to better understand aviation emissions, and working to improve the EDMS modeling capability.  Developments planned in the near future are intended to further refine the fidelity, increase the flexibility and expand the capabilities of EDMS.