Proposed Updates to AERMOD 

Modeling System

Roger W. Brode

U.S. EPA/OAQPS/AQAD/AQMG

11th Modeling Conference

Research Triangle Park, NC

August 12, 2015

8/12/2015 U.S. Environmental Protection Agency 1
Introduction

• Beginning with version 12345, AERMOD and AERMET 

incorporated non-Default/BETA options to address concerns 

regarding model overpredictions during stable/low-wind 

conditions:

– These non-Default/BETA enhancements included the LOW_WIND option in 

AERMOD and the ADJ_U* option in AERMET;

– Proposed updates to these non-Default/BETA options in version 15181 are 

discussed here.

• Additional updates to the regulatory options in AERMOD are 

being proposed, including a buoyant line source option and 

options to model capped and horizontal stacks.

• Proposed updates are subject to public review and comment 

and would then be codified as part of the final rule action, as 

appropriate.

8/12/2015 U.S. Environmental Protection Agency 2
AERMOD Updates – Low_Wind

• Beginning with v12345, AERMOD includes nonDFAULT/BETA Low_Wind options;

– Prior to v15181, AERMOD included a LowWind1 option and a 

LowWind2 option, i.e.,

• LowWind1 eliminates the horizontal meander component and 

increases the minimum value of sigma-v from the default of 0.2 

m/s to 0.5 m/s;

• LowWind2 includes horizontal meander, but places an upper limit 

of 0.95 for the meander factor, and increases the minimum value 

of sigma-v from the default of 0.2 to 0.3 m/s.

– LowWind1 and LowWind2 are mutually exclusive

8/12/2015 U.S. Environmental Protection Agency 3
AERMOD Updates – Low_Wind (cont.)

• AERMOD v15181 includes a new LowWind3 (LW3) 

non-DFAULT/BETA option:

– LowWind3 increases minimum value of sigma-v from 0.2 to 0.3 m/s, 

consistent with the LowWind2 option, but eliminates upwind 

dispersion, consistent with the LowWind1 option;

– The LowWind3 option uses an “effective” sigma-y value that 

replicates the centerline concentration accounting for meander, but 

sets concentrations to zero (0) for receptors more than 6*sigma-y off 

the plume centerline, similar to the FASTALL option;

– EPA has proposed in the NPRM that the LowWind3 option be 

incorporated into regulatory version, while the LowWind1 and 

LowWind2 options are still available for testing & evaluation 

purposes.

8/12/2015 U.S. Environmental Protection Agency 4
AERMET/AERMOD Updates – ADJ_U*

• The Beta ADJ_U* option in AERMET associated with the Bulk 

Richardson Number (BULKRN) option has been modified to 

include a more refined method for calculating THSTAR and 

extending its applicability for very stable/low wind conditions, 

based on Luhar and Raynor (BLM, v132, 2009);

• The updated ADJ_U* option with BULKRN also includes 

modifications to subroutine TGINIT in AERMOD to calculate 

THSTAR;

• EPA has proposed in the NPRM that the ADJ_U* option (with or 

without BULKRN) be incorporated into the regulatory version of 

AERMET.

8/12/2015 U.S. Environmental Protection Agency 5
Capped and Horizontal Stacks

• A Model Clearinghouse memorandum dated July 9, 

1993, provided recommendations for modeling capped 

and horizontal stacks:

– Clearinghouse procedure involves setting the exit velocity (Vs) to 0.001 

m/s and adjusting the stack diameter (Ds) to maintain the actual flow 

rate and buoyancy of the plume;

– The PRIME numerical plume rise algorithm for building downwash 

uses the input Ds to define the initial radius of the plume – use of a 

larger effective radius may alter results in physically unrealistic ways;

– The AERMOD Implementation Guide suggests using Vs=0.001m/s 

with actual Ds as an interim solution.

8/12/2015 U.S. Environmental Protection Agency 6
Capped and Horizontal Stacks (cont.)

• Draft/BETA options for capped & horizontal stacks have 

been incorporated in AERMOD (beginning with v06341):

– Source types POINTCAP & POINTHOR used to trigger BETA options;

– User inputs actual stack exit velocity (Vs) and stack diameter (Ds);

– The Model Clearinghouse procedure is used for non-downwash sources;

– For the POINTHOR option with downwash the exit velocity is assigned 

as the initial horizontal velocity of the plume;

– For the POINTCAP option with downwash, the initial plume radius is 

assigned as 2*Ds to account for initial plume spread from the cap, and 

the initial horizontal velocity of the plume is assigned as the initial exit 

velocity specified by the user divided by 4 to account for suppressed 

momentum and buoyancy.

8/12/2015 U.S. Environmental Protection Agency 7
Buoyant Line Sources

• Appendix W currently recommends the use of the Buoyant 

Line and Point (BLP) model for buoyant line sources;

• The BLP model is based on outdated dispersion theory 

and the meteorological data processor for BLP, 

PCRAMMET, is not capable of processing the current 

meteorological data, including the 1-minute ASOS data;

• The BLP model also lacks the processing options to 

support the form of the 1-hr NO2, 1-hr SO2 and 24-hr 

PM2.5 NAAQS.

8/12/2015 U.S. Environmental Protection Agency 8
Buoyant Line Sources (cont.)

• Beginning with v15181, AERMOD includes an option to 

model buoyant line sources, using the BUOYLINE source 

type;

• The BUOYLINE option in AERMOD model allows for 

modeling of buoyant line sources using meteorological 

data processed through the AERMET meteorological 

processor;

• The BUOYLINE option in AERMOD also allows use of the 

processing options to support the form of the 1-hr NO2, 1-

hr SO2 and 24-hr PM2.5 NAAQS.

8/12/2015 U.S. Environmental Protection Agency 9
Evaluation of AERMET/AERMOD Updates

• The proposed Beta ADJ_U* option in AERMET and Low_Wind

option in AERMOD have been evaluated based on several 

relevant field studies, including:

– The 1993 Cordero Rojo surface coal mine fugitive dust study in eastern 

Wyoming based on 24-hr PM10 concentrations (using v14134);

– The 1974 NOAA Oak Ridge, TN, tracer study for a low-level release on 

the Oak Ridge peninsula with sampling arcs at 100m, 200m, and 400m, 

and wind speeds ranging from 0.15 to 0.73m/s (10 of 11 cases < 0.5m/s);;

– The 1974 NOAA Idaho Falls, ID, tracer study for a low-level release with 

sampling arcs at 100m, 200m, and 400m, and wind speeds ranging from 

0.75 to 1.93m/s (4 of 11 cases < 1.0m/s);

8/12/2015 U.S. Environmental Protection Agency 10
Model Evaluation Caveats

• Caveats regarding model evaluation:

– Evaluating performance of dispersion models is a complex 

endeavor and results may be affected by errors or uncertainties 

regarding the correct model inputs, including emission rates, source 

characteristics, surface characteristics and meteorological data;

– Errors or uncertainties regarding the interpretation of “observed” 

concentrations may also significantly affect the conclusions 

regarding model performance;

– The potential impact of these caveats on conclusion regarding 

model performance are likely to be exaggerated in cases with very 

low wind speeds since results may be highly sensitive to relative 

small “errors” in important inputs or assumptions.

8/12/2015 U.S. Environmental Protection Agency 11
Evaluation of Beta Options

• Surface Coal Mine PM10 Study

– Cordero Rojo Mine in eastern Wyoming

– Two-month Field Study in 1993 to evaluate new emission factor 

and dispersion model options

– Evaluated 24-hour averages for PM-10 and TSP

– Majority of emissions (~75%) from roadways

– Cox-Tikvart protocol for determining the “best performing” model 

applied to give “confidence intervals” on model performance

• Results presented are for ADJ_U* and LW1 and LW2 

based on v14134, but are likely to be similar for v15181

8/12/2015 U.S. Environmental Protection Agency 12
Evaluation of Beta Options

8/12/2015 U.S. Environmental Protection Agency 13
Evaluation of Beta Options – CPM

8/12/2015 U.S. Environmental Protection Agency 14

Note: Smaller value of CPM indicates “better” performance
Evaluation of Beta Options - MCM

8/12/2015 U.S. Environmental Protection Agency 15

Note: If MCM confidence interval spans zero performance differences not statistically significant
Summary of Cordero PM10 Evaluation

• Use of the proposed ADJ_U* option in AERMET 

appears to significantly improve model 

performance for this study;

– The confidence intervals for the Model Comparison 

Measure (MCM) do not cross zero when comparing 

results with ADJ_U* vs. no ADJ_U*;

– The LW1 and LW2 options in AERMOD appear to 

have limited affect on modeled performance.

8/12/2015 U.S. Environmental Protection Agency 16
Oak Ridge and Idaho Falls Evaluations

• EPA’s evaluations for the 19974 Oak Ridge and Idaho Falls deviated in 

some respects from the original evaluations conducted by AECOM/API:

– EPA assumed a surface roughness of 0.6m for Oak Ridge as compared to 0.2m 

assumed by AECOM;

– EPA assumed a wind measurement height of 10m for Oak Ridge, due to the fact that 

the observed wind speeds were derived from laser anemometry from lasers sited on 

the top on nearby ridges, as compared to 2m assumed by AECOM;

– Also note that the Oak Ridge study area is located in a hilly area, with terrain 

elevations varying about 40m across the study area. Neither the AECOM nor EPA 

evaluations have incorporated terrain elevations in the analysis;

– EPA assumed a surface roughness of 0.08m for Idaho Falls, as compared to 

AECOM’s assumption of 0.15m for February and 0.3m for other months (the study 

spanned from Feb. to May);

– EPA assumed a release height of 3m for Idaho Falls, based on information presented 

in the NOAA Technical Memorandum and as assumed by other researchers, as 

compared to a 1.5m release height assumed by AECOM.

8/12/2015 U.S. Environmental Protection Agency 17
Oak Ridge, TN, 

Study Area

8/12/2015 U.S. Environmental Protection Agency 18
8/12/2015 U.S. Environmental Protection Agency 19

0

500

1000

1500

0 500 1000 1500

Predicted (μg/m3)

Observed (μg/m3)

Oak Ridge: Paired Plot - w/o ADJ_U* - NoLW Option - v15181

Obs vs AERMOD (Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=10

Predicted / Observed

Receptor Arcs

Oak Ridge: Residual Plot vs. DW Dist - w/o ADJ_U* - NoLW Option - v15181

Pred (AERMOD Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) vs Obs

Oak Ridge Results with v15181 Default Options

Paired Conc by Arc Pred/Obs by Arc
8/12/2015 U.S. Environmental Protection Agency 20

0

100

200

300

400

0 100 200 300 400

Predicted (μg/m3)

Observed (μg/m3)

Oak Ridge: Paired Plot - No ADJ_U* - LowWind2 Option - v14134

Obs vs AERMOD (Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=10

Predicted / Observed

Receptor Arcs

Oak Ridge: Residual Plot vs. DW Dist - No ADJ_U* - LW2 Option - v14134

Pred (AERMOD Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) vs Obs

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Oak Ridge: Paired Plot - w/o ADJ_U* - LowWind3 Option - v15181

Obs vs AERMOD (Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=10

Predicted / Observed

Receptor Arcs

Oak Ridge: Residual Plot vs. DW Dist - w/o ADJ_U* - LW3 Option - v15181

Pred (AERMOD Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) vs Obs

v14134 with No ADJ & LW2 v15181 with No ADJ & LW3
8/12/2015 U.S. Environmental Protection Agency 21

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Oak Ridge: Paired Plot - With ADJ_U* - NoLW Option - v14134

Obs vs AERMOD (Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Oak Ridge: Paired Plot - With ADJ_U* - NoLW Option - v15181

Obs vs AERMOD (Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=10

Predicted / Observed

Receptor Arcs

Oak Ridge: Residual Plot vs. DW Dist - With ADJ_U* - NoLW Option - v15181

Pred (AERMOD Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) vs Obs

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=10

Predicted / Observed

Receptor Arcs

Oak Ridge: Residual Plot vs. DW Dist - With ADJ_U* - NoLW Option - v14134

Pred (AERMOD Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) vs Obs

v14134 with ADJ & NoLW v15181 with ADJ & NoLW
8/12/2015 U.S. Environmental Protection Agency 22

0

25

50

75

100

0 25 50 75 100

Predicted (μg/m3)

Observed (μg/m3)

Oak Ridge: Paired Plot - With ADJ_U* - LowWind2 Option - v14134

Obs vs AERMOD (Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=10

Predicted / Observed

Receptor Arcs

Oak Ridge: Residual Plot vs. DW Dist - With ADJ_U* - LW2 Option - v14134

Pred (AERMOD Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) vs Obs

0

25

50

75

100

0 25 50 75 100

Predicted (μg/m3)

Observed (μg/m3)

Oak Ridge: Paired Plot - With ADJ_U* - LowWind3 Opt - v15181

Obs vs AERMOD (Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=10

Predicted / Observed

Receptor Arcs

Oak Ridge: Residual Plot vs. DW Dist - With ADJ_U* - LowWind3 Opt - v15181

Pred (AERMOD Base 1-Layer, Vector WS, 10m-Zref, 0.6m-Zo) vs Obs

v14134 with ADJ_U* & LW2 v15181 with ADJ_U* & LW3
8/12/2015 U.S. Environmental Protection Agency 23

Idaho Falls, ID, 

Study Area
8/12/2015 U.S. Environmental Protection Agency 24

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Idaho Falls: Paired Plot - He=3m - 0.08m Zo - w/o ADJ_U* - NoLW Option - v15181

Obs (unfitted) vs AERMOD (Degraded 1-Layer, Scalar WS) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=11

Predicted / Observed

Receptor Arcs

Idaho Falls: Resid Plot vs. DW Dist - He=3m - 0.08m Zo - w/o ADJ_U* - NoLW Option - v15181

Pred (AERMOD Degraded 1-Layer, Scalar WS) vs Obs (unfitted)

Idaho Falls Results with v15181 Default Options

Paired Conc by Arc Pred/Obs by Arc
8/12/2015 U.S. Environmental Protection Agency 25

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Idaho Falls: Paired Plot - He=3m - 0.08m Zo - w/o ADJ_U* - LowWind3 Option - v15181

Obs (unfitted) vs AERMOD (Degraded 1-Layer, Scalar WS) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=11

Predicted / Observed

Receptor Arcs

Idaho Falls: Resid Plot vs. DW Dist - He=3m - 0.08m Zo - w/o ADJ_U* - LW3 Option - v15181

Pred (AERMOD Degraded 1-Layer, Scalar WS) vs Obs (unfitted)

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Idaho Falls: Paired Plot - He=3m - 0.08m Zo - No ADJ_U* - LowWind2 Option - v14134

Obs (unfitted) vs AERMOD (Base 1-Layer, Scalar WS) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=11

Predicted / Observed

Receptor Arcs

Idaho Falls: Resid Plot vs. DW Dist - He=3m - 0.08m Zo - No ADJ_U* - LW2 Option - v14134

Pred (AERMOD Base 1-Layer, Scalar WS) vs Obs (unfitted)

v14134 w/o ADJ_U* & LW2 v15181 w/o ADJ_U* & LW3

Degraded 1-layer

No Delta_T and No SA
8/12/2015 U.S. Environmental Protection Agency 26

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Idaho Falls: Paired Plot - He=3m - 0.08m Zo - With ADJ_U* - NoLW Option - v4134

Obs (unfitted) vs AERMOD (Base 1-Layer, Scalar WS) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=11

Predicted / Observed

Receptor Arcs

Idaho Falls: Resid Plot vs. DW Dist - He=3m - 0.08m Zo - With ADJ_U* - NoLW Option - v4134

Pred (AERMOD Base 1-Layer, Scalar WS) vs Obs (unfitted)

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Idaho Falls: Paired Plot - He=3m - 0.08m Zo - With ADJ_U* - NoLW Option - v15181

Obs (unfitted) vs AERMOD (Degraded 1-Layer, Scalar WS) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=11

Predicted / Observed

Receptor Arcs

Idaho Falls: Resid Plot vs. DW Dist - He=3m - 0.08m Zo - With ADJ_U* - NoLW Option - v15181

Pred (AERMOD Degraded 1-Layer, Scalar WS) vs Obs (unfitted)

v14134 with ADJ_U* & NoLW v15181 with ADJ_U* & NoLW

Degraded 1-layer

No Delta_T and No SA
8/12/2015 U.S. Environmental Protection Agency 27

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Idaho Falls: Paired Plot - He=3m - 0.08m Zo - With ADJ_U* - LowWind2 Option - v14134

Obs (unfitted) vs AERMOD (Base 1-Layer, Scalar WS) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=11

Predicted / Observed

Receptor Arcs

Idaho Falls: Resid Plot vs. DW Dist - He=3m - 0.08m Zo - With ADJ_U* - LW2 Option - v14134

Pred (AERMOD Base 1-Layer, Scalar WS) vs Obs (unfitted)

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Idaho Falls: Paired Plot - He=3m - 0.08m Zo - With ADJ_U* - LowWind3 Option - v15181

Obs (unfitted) vs AERMOD (Degraded 1-Layer, Scalar WS) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=11

Predicted / Observed

Receptor Arcs

Idaho Falls: Resid Plot vs. DW Dist - He=3m - 0.08m Zo - With ADJ_U* - LW3 Option - v15181

Pred (AERMOD Degraded 1-Layer, Scalar WS) vs Obs (unfitted)

v14134 with ADJ_U* & LW2 v15181 with ADJ_U* & LW3

Degraded 1-layer

No Delta_T and No SA
8/12/2015 U.S. Environmental Protection Agency 28

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Idaho Falls: Paired Plot - He=3m - 0.08m Zo - Without ADJ_U* - NoLW Option - v15181

Obs (unfitted) vs AERMOD (Deg 2-Layer, 8-1m DT, Scalar WS) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=11

Predicted / Observed

Receptor Arcs

Idaho Falls: Resid Plot vs. DW Dist - He=3m - 0.08m Zo - w/o ADJ_U* - NoLW Option - v15181

Pred (Deg 2-Layer, 8-1m DT, Scalar WS) vs Obs (unfitted)

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Idaho Falls: Paired Plot - He=3m - 0.08m Zo - No ADJ_U* - NoLW Option - v14134

Obs (unfitted) vs AERMOD (Base 1-Layer, Scalar WS) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=11

Predicted / Observed

Receptor Arcs

Idaho Falls: Resid Plot vs. DW Dist - He=3m - 0.08m Zo - No ADJ_U* - NoLW Option - v14134

Pred (AERMOD Base 1-Layer, Scalar WS) vs Obs (unfitted)

v14134 w/o ADJ_U* & NoLW v15181 w/o ADJ_U* & NoLW

Degraded 2-layer

w/ 8-1m DT and No SA
8/12/2015 U.S. Environmental Protection Agency 29

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Idaho Falls: Paired Plot - He=3m - 0.08m Zo - With ADJ_U* - LowWind2 Option - v14134

Obs (unfitted) vs AERMOD (Deg 2-Layer, 8-1m DT, Scalar WS) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=11

Predicted / Observed

Receptor Arcs

Idaho Falls: Resid Plot vs. DW Dist - He=3m - 0.08m Zo - With ADJ_U* - LW2 Option - v14134

Pred (AERMOD (Deg 2-Layer, 8-1m DT, Scalar WS) vs Obs (unfitted)

0

50

100

150

200

0 50 100 150 200

Predicted (μg/m3)

Observed (μg/m3)

Idaho Falls: Paired Plot - He=3m - 0.08m Zo - With ADJ_U* - LowWind3 Option - v15181

Obs (unfitted) vs AERMOD (Deg 2-Layer, 8-1m DT, Scalar WS) Pred Arc-Max @ 3 DW Arcs

100-m Arc

200-m Arc

400-m Arc

0.01

0.10

1.00

10.00

100.00

100 - ns=11 200 - ns=11 400 - ns=11

Predicted / Observed

Receptor Arcs

Idaho Falls: Resid Plot vs. DW Dist - He=3m - 0.08m Zo - With ADJ_U* - LW3 Option - v15181

Pred (Deg 2-Layer, 8-1m DT, Scalar WS) vs Obs (unfitted)

v14134 with ADJ_U* & LW2 v15181 with ADJ_U* & LW3

Degraded 2-layer

w/ 8-1m DT and No SA
Summary

• EPA has proposed in the NPRM that the following 

options be incorporated into the regulatory versions of 

AERMOD and AERMET:

– The ADJ_U* option in AERMET;

– The LowWind3 option in AERMOD;

– The BUOYLINE option in AERMOD for modeling buoyant line 

sources; and

– The POINTCAP and POINTHOR source type options in 

AERMOD to model capped and horizontal stacks.

8/12/2015 U.S. Environmental Protection Agency 30