AQ_GEN_PLNG_20220404_SIP_RH-SIP_AppE2e

Appendix E-2e

Regional Haze Modeling for Southeastern VISTAS II
Regional Haze Analysis Project 2028elv3 CAMx
Version 6.40 12km VISTAS and EPA 12km
Continental Grid Comparison Report

Benchmark Run #6

August 17, 2020

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CAMx Benchmarking Report #5

Regional Haze Modeling for Southeastern
VISTAS II Regional Haze Analysis Project
2028elv3 CAMx Version 6.40 12km VISTAS
and EPA 12km Continental Grid Comparison
Report

Task 6 Benchmark Report #5
Covering Benchmark Run #6

Prepared for:

Southeastern States Air Resource Managers, Inc.
(SESARM)

205 Corporate Center Drive, Suite D
Stockbridge, GA 30281-7383

Under Contract No. V-2018-03-01

Prepared by:
Alpine Geophysics, LLC
387 Pollard Mine Road
Burnsville, NC 28714

and

Eastern Research Group, Inc.
1600 Perimeter Park Dr., Suite 200
Morrisville, NC 27560

Final – August 17, 2020

Alpine Project Number: TS-527
ERG Project Number: 4133.00.006

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August 17, 2020 i

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CAMx Benchmarking Report #5

August 17, 2020 ii
Contents
Page
1.0 INTRODUCTION ............................................................................................................1
1.1 Overview ...............................................................................................................1
1.2 CAMx 6.40 2028elv3 VISTAS12 and EPA 12US2 Comparison ........................3
2.0 DEVELOPMENT OF VISTAS12 INPUTS .....................................................................4
3.0 CONFIRMATION METHODOLOGY ............................................................................4
3.1 CAMx Species Mapping .......................................................................................6
4.0 VISTAS12 AND 12US2 CAMX 6.40 2018ELV3 COMPARISON ................................6
4.1 Ozone ....................................................................................................................6
4.2 PM2.5 ...................................................................................................................30
4.3 Sulfate .................................................................................................................53
4.4 Nitrate .................................................................................................................76
4.5 Organic Matter (OM) ..........................................................................................99
5.0 CONCLUSIONS...........................................................................................................122

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TABLES
Table 1-1. VISTAS II Modeling Domain Specifications ................................................................3
Table 3-1. Species Mapping from CAMx into Aggregated Species ...............................................6
Table 4-1. Comparison of 2028elv3 CAMx 6.40 VISTAS12 and 12US2 Simulation of Ozone
Concentrations (ppb). Hours with the top 10 maximum positive and maximum
negative differences are shown. ...........................................................................................8
Table 4-2. Comparison of 2028elv3 CAMx 6.40 VISTAS12 and 12US2 Simulation of PM2.5
Concentrations (µg/m3). Hours with the top 10 maximum positive and maximum
negative differences are shown. .........................................................................................31
Table 4-3. Comparison of 2028elv3 CAMx 6.40 VISTAS12 and 12US2 Simulation of
Sulfate Concentrations (µg/m3). Hours with the top 10 maximum positive and
maximum negative differences are shown. ........................................................................54
Table 4-4. Comparison of 2028elv3 CAMx 6.40 VISTAS12 and 12US2 Simulation of
Nitrate Concentrations (µg/m3). Hours with the top 10 maximum positive and
maximum negative differences are shown. ........................................................................77
Table 4-5. Comparison of 2028elv3 CAMx 6.40 VISTAS12 and 12US2 Simulation of
Organic Matter Concentrations (µg/m3). Hours with the top 10 maximum positive and
maximum negative differences are shown. ......................................................................100

FIGURES
Figure 1-1. Map of 12km CAMx Modeling Domains. VISTAS12 Domain Represented as
Inner Red Domain. ...............................................................................................................3
Figure 4-1: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Maximum Positive Difference) ...........................9
Figure 4-2: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Second Highest Positive Difference) ................10
Figure 4-3: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Third Highest Positive Difference) ...................11
Figure 4-4: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Fourth Highest Positive Difference) .................12
Figure 4-5: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Fifth Highest Positive Difference) ....................13
Figure 4-6: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Sixth Highest Positive Difference) ...................14

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August 17, 2020 v
Figure 4-7: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Seventh Highest Positive Difference) ...............15
Figure 4-8: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Eighth Highest Positive Difference) .................16
Figure 4-9: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Ninth Highest Positive Difference) ...................17
Figure 4-10: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Tenth Highest Positive Difference) ...................18
Figure 4-11: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Maximum Negative Difference) .......................19
Figure 4-12: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Second Highest Negative Difference)...............20
Figure 4-13: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Third Highest Negative Difference) .................21
Figure 4-14: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Fourth Highest Negative Difference) ................22
Figure 4-15: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Fifth Highest Negative Difference)...................23
Figure 4-16: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Sixth Highest Negative Difference) ..................24
Figure 4-17: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Seventh Highest Negative Difference) .............25
Figure 4-18: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Eighth Highest Negative Difference) ................26
Figure 4-19: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Ninth Highest Negative Difference) .................27
Figure 4-20: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Tenth Highest Negative Difference) .................28
Figure 4-21: Scatterplot Comparing 24-hour Average Predicted Ozone Concentrations (ppb)
for All Days at all IMPROVE Monitor Locations for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations Performed by V ISTAS (Alpine)........................29
Figure 4-22: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Positive Difference) ..................32
Figure 4-23: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Positive Difference) .........33
Figure 4-24: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Positive Difference) ............34

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August 17, 2020 vi
Figure 4-25: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Positive Difference) ..........35
Figure 4-26: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Positive Difference) .............36
Figure 4-27: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Positive Difference) .............37
Figure 4-28: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Seventh Highest Positive Difference) ........38
Figure 4-29: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Positive Difference) ..........39
Figure 4-30: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Positive Difference) ............40
Figure 4-31: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Positive Difference) ............41
Figure 4-32: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Negative Difference) ................42
Figure 4-33: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Negative Difference) ........43
Figure 4-34: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Negative Difference) ...........44
Figure 4-35: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Negative Difference) .........45
Figure 4-36: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Negative Difference) ............46
Figure 4-37: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Negative Difference) ...........47
Figure 4-38: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Seventh Highest Negative Difference) .......48
Figure 4-39: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Negative Difference) .........49
Figure 4-40: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Negative Difference) ..........50
Figure 4-41: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Negative Difference) ..........51
Figure 4-42: Scatterplot Comparing 24-hour Average Predicted PM2.5 Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.40 on

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August 17, 2020 vii
VISTAS12 and 12US2 Domains 2028elv3 Simulations Performed by VISTAS
(Alpine). .............................................................................................................................52
Figure 4-43: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Positive Difference) ..................55
Figure 4-44: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Positive Difference) .........56
Figure 4-45: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Positive Difference) ............57
Figure 4-46: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Positive Difference) ..........58
Figure 4-47: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Positive Difference) .............59
Figure 4-48: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Positive Difference) .............60
Figure 4-49: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations ......................................................................61
Figure 4-50: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Positive Difference) ..........62
Figure 4-51: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Positive Difference) ............63
Figure 4-52: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Positive Difference) ............64
Figure 4-53: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Negative Difference) ................65
Figure 4-54: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Negative Difference) ........66
Figure 4-55: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Negative Difference) ...........67
Figure 4-56: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Negative Difference) .........68
Figure 4-57: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Negative Difference) ............69
Figure 4-58: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Negative Difference) ...........70
Figure 4-59: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Seventh Highest Negative Difference) .......71

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August 17, 2020 viii
Figure 4-60: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Negative Difference) .........72
Figure 4-61: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Negative Difference) ..........73
Figure 4-62: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Negative Difference) ..........74
Figure 4-63: Scatterplot Comparing 24-hour Average Predicted Sulfate Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations Performed by VISTAS
(Alpine). .............................................................................................................................75
Figure 4-64: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Positive Difference) ..................78
Figure 4-65: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Positive Difference) .........79
Figure 4-66: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Positive Difference) ............80
Figure 4-67: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Positive Difference) ..........81
Figure 4-68: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Positive Difference) .............82
Figure 4-69: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Positive Difference) .............83
Figure 4-70: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Seventh Highest Positive Difference) ........84
Figure 4-71: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Positive Difference) ..........85
Figure 4-72: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Positive Difference) ............86
Figure 4-73: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Positive Difference) ............87
Figure 4-74: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Negative Difference) ................88
Figure 4-75: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Negative Difference) ........89
Figure 4-76: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Negative Difference) ...........90

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Figure 4-77: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Negative Difference) .........91
Figure 4-78: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Negative Difference) ............92
Figure 4-79: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Negative Difference) ...........93
Figure 4-80: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Seventh Highest Negative Difference) .......94
Figure 4-81: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Negative Difference) .........95
Figure 4-82: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Negative Difference) ..........96
Figure 4-83: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Negative Difference) ..........97
Figure 4-84: Scatterplot Comparing 24-hour Average Predicted Nitrate Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations Performed by VISTAS
(Alpine). .............................................................................................................................98
Figure 4-85: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Maximum Positive
Difference) .......................................................................................................................101
Figure 4-86: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Second Highest Positive
Difference) .......................................................................................................................102
Figure 4-87: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Third Highest Positive
Difference) .......................................................................................................................103
Figure 4-88: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Fourth Highest Positive
Difference) .......................................................................................................................104
Figure 4-89: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Fifth Highest Positive
Difference) .......................................................................................................................105
Figure 4-90: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Sixth Highest Positive
Difference) .......................................................................................................................106
Figure 4-91: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Seventh Highest Positive
Difference) .......................................................................................................................107

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Figure 4-92: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Eighth Highest Positive
Difference) .......................................................................................................................108
Figure 4-93: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Ninth Highest Positive
Difference) .......................................................................................................................109
Figure 4-94: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Tenth Highest Positive
Difference) .......................................................................................................................110
Figure 4-95: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Maximum Negative
Difference) .......................................................................................................................111
Figure 4-96: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Second Highest Negative
Difference) .......................................................................................................................112
Figure 4-97: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Third Highest Negative
Difference) .......................................................................................................................113
Figure 4-98: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Fourth Highest Negative
Difference) .......................................................................................................................114
Figure 4-99: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Fifth Highest Negative
Difference) .......................................................................................................................115
Figure 4-100: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Sixth Highest Negative
Difference) .......................................................................................................................116
Figure 4-101: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Seventh Highest Negative
Difference) .......................................................................................................................117
Figure 4-102: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Eighth Highest Negative
Difference) .......................................................................................................................118
Figure 4-103: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Ninth Highest Negative
Difference) .......................................................................................................................119
Figure 4-104: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Tenth Highest Negative
Difference) .......................................................................................................................120

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Figure 4-105: Scatterplot Comparing 24-hour Average Predicted Organic Matter
Concentrations (µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx
6.40 on VISTAS12 and 12US2 Domains 2028elv3 Simulations Performed by
VISTAS (Alpine). ............................................................................................................121

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Abbreviations/Acronym List

Alpine Alpine Geophysics, LLC
BNDEXTR Boundary extraction program
CAMx Comprehensive Air quality Model with eXtensions
CONUS Continental U.S.
dv Deciview
ERG Eastern Research Group, Inc.
EPA Environmental Protection Agency
FCRS Crustal fraction of PM
FLM Federal Land Manager
FORTRAN Formula Translation programming language
FPRM Fine other primary (diameter ≤ 2.5µm)
FR Federal Register
IMPROVE Interagency Monitoring of Protected Visual Environments
km kilometer
µg/m3 microgram per cubic meter
NA Sodium
NAAQS National Ambient Air Quality Standard
OAQPS Office of Air Quality Planning and Standards
O3 Ozone
OM Organic matter
PCL Particulate chlorine
PEC Primary elemental carbon
PM2.5 Fine particle; primary particulate matter less than or equal to 2.5 microns
in aerodynamic diameter
PNH4 Particulate ammonium
PNO3 Particulate nitrate
POA Primary Organic Aerosol
ppb Parts per billion
PSO4 Particulate sulfate
R2 Pearson correlation coefficient squared
RHR Regional Haze Rule
SESARM Southeastern States Air Resource Managers, Inc.
SIP State Implementation Plan
SO2 Sulfur dioxide
SOA Secondary organic aerosol
U.S. United States
VISTAS Visibility Improvement – State and Tribal Association of the Southeast

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1.0 INTRODUCTION
1.1 Overview
Southeastern States Air Resource Managers, Inc. (SESARM) has been designated by the
United States Environmental Protection Agency (EPA) as the entity responsible for coordinating
regional haze evaluations for the ten Southeastern states of Alabama, Florida, Georgia,
Kentucky, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, and West Virginia.
The Eastern Band of Cherokee Indians and the Knox County, Tennessee local air pollution
control agency are also participating agencies. These parties are collaborating through the
Regional Planning Organization known as Visibility Improvement - State and Tribal Association
of the Southeast (VISTAS) in the technical analyses and planning activities associated with
visibility and related regional air quality issues. VISTAS analyses will support the VISTAS
states in their responsibility to develop, adopt, and implement their State Implementation Plans
(SIPs) for regional haze.
The state and local air pollution control agencies in the Southeast are mandated to protect
human health and the environment from the impacts of air pollutants. They are responsible for
air quality planning and management efforts including the evaluation, development, adoption,
and implementation of strategies controlling and managing all criteria air pollutants including
fine particles and ozone as well as regional haze. This project will focus on regional haze and
regional haze precursor emissions. Control of regional haze precursor emissions will have the
additional benefit of reducing criteria pollutants as well.
The 1999 Regional Haze Rule (RHR) identified 18 Class I Federal areas (national parks
greater than 6,000 acres and wilderness areas greater than 5,000 acres) in the VISTAS region.
The 1999 RHR required states to define long-term strategies to improve visibility in Federal
Class I national parks and wilderness areas. States were required to establish baseline visibility
conditions for the period 2000-2004, natural visibility conditions in the absence of anthropogenic
influences, and an expected rate of progress to reduce emissions and incrementally improve
visibility to natural conditions by 2064. The original RHR required states to improve visibility on
the 20% most impaired days and protect visibility on the 20% least impaired days.1 The RHR

1 RHR summary data is available at: http://vista.cira.colostate.edu/Improve/rhr-summary-data/

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requires states to evaluate progress toward visibility improvement goals every five years and
submit revised SIPs every ten years.
EPA finalized revisions to various requirements of the RHR in January 2017 (82 FR
3078) that were designed to strengthen, streamline, and clarify certain aspects of the agency’s
regional haze program including:
A. Strengthening the Federal Land Manager (FLM) consultation requirements to ensure that
issues and concerns are brought forward early in the planning process.
B. Updating the SIP submittal deadlines for the second planning period from July 31, 2018
to July 31, 2021 to ensure that they align where applicable with other state obligations
under the Clean Air Act. The end date for the second planning period remains 2028; that
is, the focus of state planning will be to establish reasonable progress goals for each Class
I area against which progress will be measured during the second planning period. This
extension will allow states to incorporate planning for other Federal programs while
conducting their regional haze planning. These other programs include: the Mercury and
Air Toxics Standards, the 2010 1-hour sulfur dioxide (SO2) National Ambient Air
Quality Standards (NAAQS); the 2012 annual fine particle (PM2.5) NAAQS; and the
2008 and 2015 ozone NAAQS.
C. Adjusting interim progress report submission deadlines so that second and subsequent
progress reports will be due by: January 31, 2025; July 31, 2033; and every ten years
thereafter. This means that one progress report will be required midway through each
planning period.
D. Removing the requirement for progress reports to take the form of SIP revisions. States
will be required to consult with FLMs and obtain public comment on their progress
reports before submission to the EPA. EPA will be reviewing but not formally approving
or disapproving these progress reports.
The RHR defines “clearest days” as the 20% of monitored days in a calendar year with
the lowest deciview (dv) index values. “Most impaired days” are defined as the 20% of

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monitored days in a calendar year with the highest amounts of anthropogenic visibility
impairment. The long-term strategy and the reasonable progress goals must provide for an
improvement in visibility for the most impaired days since the baseline period and ensure no
degradation in visibility for the clearest days since the baseline period.
1.2 CAMx 6.40 2028elv3 VISTAS12 and EPA 12US2 Comparison
The VISTAS II air quality modeling is being performed on a smaller computational grid
than EPA used in developing the 2011el platform. The use of the smaller domain is designed to
allow SESARM to more efficiently look at air quality issues in the southeastern US.
Alpine has executed two air quality simulations for the 2028elv3 base year modeling
platform; one run with CAMx 6.40 over the EPA continental US domain (12US2) and one for
the VISTAS12 domain. The domains are presented in Figure 1-1 with the 12US2 domain as the
outer grid and the VISTAS12 domain is shown as the red box. The domain definitions for the
two domains are presented in Table 1-1.
Table 1-1. VISTAS II Modeling Domain Specifications
Domain Columns Rows Vertical Layers X Origin (km) Y Origin (km)
CONUS_12 396 246 25 -2,412 -1,620
VISTAS_12 269 242 25 -912 -1,596

Figure 1-1. Map of 12km CAMx Modeling Domains. VISTAS12 Domain Represented as
Inner Red Domain.

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2.0 DEVELOPMENT OF VISTAS12 INPUTS
The inputs for the VISTAS12 domain were developed by extracting a subdomain from
the CAMx ready model inputs (commonly referred to as windowing). The meteorology and
emissions inputs were windowed using a slightly modified version of the CAMx utility program
“window”.2 The only required change to the distributed version program is to allow the program
to window three-dimension files instead of just two-dimensional files. The CAMx ozone column
and watermask inputs were windowed using new FORTRAN programs using the same
windowing algorithm as is contained in the “window” code. The windowing code was checked
graphically to assure that the VISTAS12 results were consistent with the 12US2 results. The
boundary and initial conditions for the VISTAS12 domain will be extracted from the 12US2
three-dimensional output files using the CAMx BNDEXTR program.
Two issues have been identified that have noted impact on the use of the VISTAS12
domain relative to the 12US2 domain.3 The first, and likely the most significant, noted issue is a
time-step difference at the boundary where concentration conditions from outside of the domain
are injected into the modeling domain at one hour intervals compared to the model generated
(sub-hourly) time-step interval within the modeling domain. These differences can create initial,
significant concentration gradients along the boundary that can be carried through the episode
and transported to grid cells within the modeling domain. The second issue is related to the time
step in the model. The time step is determined by the maximum wind in the modeling domain. If
the highest wind in the 12US2 domain occurs somewhere outside the VISTAS12 domain, the
time step in the 12US2 simulation will be longer than in the VISTAS12 domain.
We note that in modeling the VISTAS12 domain with 12US2 boundary conditions, both
of these issues are exacerbated in the modeling due to large emission sources located near the
boundary of the 12US2/VISTAS12 boundary, particularly in Canada.
3.0 CONFIRMATION METHODOLOGY
The presented comparisons of model simulations are based on hourly differences in
ozone, PM2.5, Organic Matter (OM), Particulate Nitrate (PNO3), and Particulate Sulfate (PSO4).

2 http://www.camx.com/getmedia/88755b80-6992-4f07-bcaa-596d05e1b4b8/window-6may13_1.tgz
3 Brian Timin, EPA Office of Air Quality Planning and Standards (OAQPS) personal communication October 11, 2018.

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The metric for comparison are the absolute difference (Equation 1) and percent difference
(Equation 2) defined as:
(Equation 1) (𝐶𝐶𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉12 −𝐶𝐶12𝑈𝑈𝑉𝑉2 )

(Equation 2) (𝐶𝐶𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉12 −𝐶𝐶12𝑈𝑈𝑉𝑉2)(𝐶𝐶12𝑈𝑈𝑉𝑉2)

Where CVISTAS12 is the concentration at each grid cell hour for the CAMx simulation over
the VISTAS12 simulation and C12US2 is the concentration at each grid cell hour for the CAMx
simulation over the 12US2.
To facilitate the comparison of the results over the same spatial domain, the 12US2
simulation output files were windowed onto the VISTAS2 domain using the I/O API4 m3wndw
code.
The results are presented for the hours with the largest difference between the
simulations. Each table presents the hours with the top 10 positive and negative absolute
differences. Spatial maps are presented for the hours with the top 10 highest positive and
negative differences. To provide context for the differences, the concentration maps are also
presented for each of the hours of high difference. On each spatial plot the maximum positive
and negative values, along with the grid cell in which these occur, are presented at the top of the
graphic. The coordinates refer to the row and columns of the cell referenced to the cell
coordinates on the bottom (column) and left (row) of the graphic. Because the CAMx results are
unduly influenced by the boundary concentrations around the edges, the analysis does not
include the edge rows and columns of the CAMx domain.
Hourly animations have also been prepared and are available on the VISTAS II project
ftp site. Where appropriate, this report also reports and interprets on the animations.

4 https://www.cmascenter.org/ioapi/

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3.1 CAMx Species Mapping
Several of the key particulate matter species of interest are combinations of CAMx output
variable. The CAMx 6.40 species mapping are presented in Table 3-1.
Table 3-1. Species Mapping from CAMx into Aggregated Species
Aggregated Species CAMx 6.40 Species
Ozone O3
PM2.5 PSO4+PNO3+PNH4+SOA1+SOA2+SOA3+SOA4+SOPA+SOPB+P
OA+PEC+FPRM+FCRS+NA+PCL
Sulfate PSO4
Nitrate PNO3
Organic Matter (OM) SOA1+SOA2+SOA3+SOA4+SOPA+SOPB+POA

4.0 VISTAS12 AND 12US2 CAMX 6.40 2018ELV3 COMPARISON
This section presents comparisons of the simulations using CAMx 6.40 performed on the
Alpine computer system using the SESARM 2028elv3 modeling platform over the VISTAS12
and 12US2 domains.
4.1 Ozone
Ozone results for the top 10 positive and negative hours are presented in tabular format in
Table 4-1. The maximum positive difference is 18.00 ppb falling to 11.76 ppb for the 10th high.
The maximum negative difference is -17.43 ppb falling to -12.19 for the 10th high. Generally the
highest positive and negative differences are occurring on relatively high ozone hours with
concentrations up to 144.19 ppb for the VISTAS12 simulation. The maximum positive and
negative percent differences are 82.1% and -16.0%, respectively.
As expected, the maximum impacts on the top 10 positive and negative hours are
occurring very near the border (Rows close to 1 or 268 and Columns near 1 or 241). As was
described in Section 2, the two CAMx simulations used the same input data, except that the
pollutant concentrations on in-flow boundary cells. For the simulation on the VISTAS12 domain
the in-flow concentrations are specified in hourly average boundary conditions extracted from
the 12US2 simulation. For the 12US2 simulation the in-flow concentrations were continuously
updated at every model-generated timestep from the cells outside the VISTAS12 domain.
Additionally, as noted in an earlier section, the CAMx model does not include emissions in the

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border cells. It would be expected that concentration differences would occur from the
differences in hourly average concentrations, versus in the instantaneous model-determined
concentrations and the CAMx model excluding emissions along the border.
The top ten positive impact hours are presented in Figures 4-1 through 4-10. The top ten
negative impact hours are presented in Figures 4-11 through 4-20. The regions of highest
differences tend to occur along the northern and western boundary and during short-term periods
of time.
Scatterplots of the daily average ozone concentrations in local standard time at the
IMPROVE monitors across all modeled days are presented in Figure 4-21. The 12US2 results
are plotted on the x-axis and the VISTAS12 results are plotted on the y-axis. The data has a high
degree of correlation with a line of best fit with a slope of 1.0002, an intercept of 0.0090 ppb and
an R2 of 0.9999.
Examination of the difference animations shows some interesting results. On many hours
the differences are fairly smooth without much horizontal difference, as seen in Figure 4-10.
Then, in a single hour, regions of small local gradients occur and the spatial field resembles
Figure 4-8. Often, over a period of several hours, these small differences disappear and the
smooth structure is restored.
These differences are likely caused by a combination of factors. The first, and likely the
most significant, noted issue is a time-step difference at the boundary where concentration
conditions from outside of the domain are injected into the modeling domain at one hour
intervals compared to the model generated (sub-hourly) time-step interval within the modeling
domain. The other difference is the time step in the integration of the CAMx model. The CAMx
model determines the time step based on the highest wind speed in the domain. When the highest
wind speed is located in the VISTAS12 region, the time step for the VISTAS12 and 12US2
simulations are the same. When the highest wind speed in the 12US2 domain occurs outside the
VISTAS12 domain, the time steps are different in the two simulations. This difference in the
time step will yield slightly different concentrations between the two region simulations.

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Table 4-1. Comparison of 2028elv3 CAMx 6.40 VISTAS12 and 12US2 Simulation of Ozone
Concentrations (ppb). Hours with the top 10 maximum positive and maximum negative
differences are shown.
Year Month Day Hour VISTAS12
Conc.
12US2
Conc.
Difference
(ppb)
Percent
Difference Column Row
Maximum Positive
2011 7 20 15 144.19 126.19 18.00 14.3% 108 240
2011 7 20 16 127.78 112.36 15.42 13.7% 107 240
2011 7 20 17 81.19 66.76 14.43 21.6% 121 241
2011 5 17 8 30.48 17.32 13.17 76.0% 60 6
2011 5 17 7 28.95 15.90 13.05 82.1% 60 5
2011 7 20 21 56.21 43.52 12.69 29.2% 107 241
2011 9 6 8 39.02 26.46 12.56 47.5% 51 2
2011 5 17 9 30.86 18.65 12.21 65.4% 267 107
2011 2 24 0 46.52 34.54 11.98 34.7% 49 3
2011 9 6 9 38.17 26.41 11.76 44.5% 51 2
Maximum Negative
2011 7 17 16 110.95 128.38 -17.43 -13.6% 92 241
2011 7 17 15 124.11 141.25 -17.14 -12.1% 90 241
2011 7 17 14 127.73 142.75 -15.03 -10.5% 90 241
2011 7 17 18 83.33 98.35 -15.02 -15.3% 93 240
2011 7 17 17 96.46 111.21 -14.74 -13.3% 92 241
2011 7 17 19 78.65 92.71 -14.06 -15.2% 92 240
2011 7 18 19 70.35 83.73 -13.38 -16.0% 89 241
2011 7 18 18 74.07 87.43 -13.36 -15.3% 89 241
2011 7 18 15 94.25 107.58 -13.34 -12.4% 88 241
2011 7 18 20 68.25 80.44 -12.19 -15.2% 90 240

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Maximum Positive Difference: July 20 at 1500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-1: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Maximum Positive Difference)

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Second Highest Positive Difference: July 20 at1600 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-2: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Second Highest Positive Difference)

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Third Highest Positive Difference: July 20 at 1700 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-3: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Third Highest Positive Difference)

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Fourth Highest Positive Difference: May 17 at 800 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-4: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Fourth Highest Positive Difference)

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Fifth Highest Positive Difference: May 17 at 700 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-5: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Fifth Highest Positive Difference)

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Sixth Highest Positive Difference: July 20 at 2100 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-6: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Sixth Highest Positive Difference)

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Seventh Highest Positive Difference: September 6 at 800 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-7: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Seventh Highest Positive Difference)

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Eighth Highest Positive Difference: May 17 at 900 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-8: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Eighth Highest Positive Difference)

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Ninth Highest Positive Difference: February 24 at 0000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-9: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Ninth Highest Positive Difference)

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Tenth Highest Positive Difference: September 6 at 900 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-10: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Tenth Highest Positive Difference)

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Maximum Negative Difference: July 17 at 1600 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-11: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Maximum Negative Difference)

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Second Highest Negative Difference: July 17 at 1500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-12: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Second Highest Negative Difference)

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Third Highest Negative Difference: July 17 at 1400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-13: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Third Highest Negative Difference)

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Fourth Highest Negative Difference: July 17 at 1800 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-14: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Fourth Highest Negative Difference)

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Fifth Highest Negative Difference: July 17 at 1700 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-15: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Fifth Highest Negative Difference)

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Sixth Highest Negative Difference: July 17 at 1900 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-16: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Sixth Highest Negative Difference)

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Seventh Highest Negative Difference: July 18 at 1900 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-17: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Seventh Highest Negative Difference)

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Eighth Highest Negative Difference: July 18 at 1800 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-18: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Eighth Highest Negative Difference)

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Ninth Highest Negative Difference: July 18 at 1500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-19: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Ninth Highest Negative Difference)

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Tenth Highest Negative Difference: July 18 at 2000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-20: Comparison of Ozone Concentrations (ppb) for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations (Tenth Highest Negative Difference)

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Figure 4-21: Scatterplot Comparing 24-hour Average Predicted Ozone Concentrations
(ppb) for All Days at all IMPROVE Monitor Locations for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations Performed by V ISTAS (Alpine).

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4.2 PM2.5
PM2.5 results for the top 10 positive and negative hours are presented in tabular format in
Table 4-2. The maximum positive difference is 383.37 µg/m3 falling to 211.49 µg/m3 for the
10th high. The maximum negative difference is -296.69 µg/m3 falling to -174.08 µg/m3 for the
10th high. The maximum positive percent difference from these days is 102.4% and negative
percent difference of -33.5%.
As expected and consistent with our ozone findings in the previous section, the maximum
impacts on the top 10 positive and negative hours are occurring very near the border. As was
described in Section 2, the two CAMx simulations used the same input data, except that the
pollutant concentrations on in-flow boundary cells. For the simulation on the VISTAS12 domain
the in-flow concentrations are specified in hourly boundary conditions extracted from the 12US2
simulation. For the 12US2 simulation the in-flow concentrations were continuously updated
from the cells outside the VISTAS12 domain. It would be expected that concentration
differences would occur from the differences in hourly average concentrations, versus in the
instantaneous concentrations. Additionally, and likely more significant to concentration
differences, the CAMx model does not include emissions from the boundary cells.
The top 10 positive difference hours are presented in Figures 4-22 through 4-31 and the
top 10 negative impact hours are presented in Tables 4-32 through 4-41. The hours of the
maximum differences are tending to occur in July 17-21. There were wildfires in Canada in the
area of the maximum difference during this period. It is not surprising that the largest difference
is occurring where noted large source emissions are input into the model near a boundary where
the time averaging of the pollutants flowing into the cells are different. On the day of the
maximum positive difference (July 21 at 0400) the maximum difference in PM2.5 concentration
was 383.43 µg/m3 ppb. At this hour at this grid cell the difference in the sulfate, nitrate, and OM
concentrations were 5.762 µg/m3, 0.835 µg/m3, 295.99 µg/m3, respectively with the difference
dominated by the differences in the OM estimates. The high local emissions dominated by OM
as is expected from wildfire emissions.
Scatterplots of the daily average PM2.5 concentrations in local standard time at the
IMPROVE monitors are presented in Figure 4-42. The 12US2 results are plotted on the x-axis

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and the VISTAS12 results are plotted on the y-axis. The data has a high degree of correlation
with a line of best fit with a slope of 1.0003, an intercept of 0.0031 µg/m3 and an R2 of 1.0000.
Examination of the difference animations often show differences along the boundary
becoming lower as the plumes along the boundary move into the domain.
Table 4-2. Comparison of 2028elv3 CAMx 6.40 VISTAS12 and 12US2 Simulation of PM2.5
Concentrations (µg/m3). Hours with the top 10 maximum positive and maximum negative
differences are shown.
Year Month Day Hour VISTAS12
Conc.
12US2
Conc.
Difference
(µg/m3)
Percent
Difference Column Row
Maximum Positive
2011 7 21 4 949.91 566.54 383.37 67.7% 104 241
2011 7 20 14 1660.05 1353.59 306.46 22.6% 107 241
2011 7 20 15 839.18 559.74 279.44 49.9% 107 241
2011 7 20 11 2740.11 2470.87 269.24 10.9% 107 241
2011 7 21 3 3176.80 2914.06 262.74 9.0% 104 241
2011 7 21 1 2369.71 2110.12 259.59 12.3% 104 241
2011 7 20 12 3022.91 2785.90 237.01 8.5% 107 241
2011 7 20 23 448.18 221.41 226.78 102.4% 102 241
2011 7 21 0 732.17 508.25 223.92 44.1% 103 241
2011 7 20 9 6964.26 6752.77 211.49 3.1% 105 241
Maximum Negative
2011 7 20 15 4857.63 5154.32 -296.69 -5.8% 105 241
2011 7 20 16 4003.88 4266.41 -262.54 -6.2% 105 241
2011 7 20 14 5167.65 5429.55 -261.90 -4.8% 106 241
2011 7 17 11 508.55 761.67 -253.12 -33.2% 89 241
2011 7 20 13 6146.56 6389.86 -243.30 -3.8% 106 241
2011 7 17 12 496.56 725.04 -228.48 -31.5% 89 241
2011 7 20 12 7718.44 7943.32 -224.88 -2.8% 106 241
2011 7 19 10 815.91 1032.49 -216.58 -21.0% 104 241
2011 7 17 10 429.07 644.79 -215.71 -33.5% 89 241
2011 7 19 9 828.90 1002.97 -174.08 -17.4% 103 241

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Maximum Positive Difference: July 21 at 400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-22: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Positive Difference)

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Second Highest Positive Difference: July 20 at 1400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-23: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Positive Difference)

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Third Highest Positive Difference: July 20 at 1500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-24: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Positive Difference)

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Fourth Highest Positive Difference: July 20 at 1100 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-25: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Positive Difference)

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Fifth Highest Positive Difference: July 21 at 300 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-26: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Positive Difference)

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Sixth Highest Positive Difference: July 21 at 100 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-27: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Positive Difference)

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Seventh Highest Positive Difference: July 20 at 1200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-28: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Seventh Highest Positive Difference)

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Eighth Highest Positive Difference: July 20 at 2300 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-29: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Positive Difference)

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Ninth Highest Positive Difference: July 21 at 0000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-30: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Positive Difference)

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Tenth Highest Positive Difference: July 20 at 900 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-31: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Positive Difference)

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Maximum Negative Difference: July 20 at 1500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-32: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Negative Difference)

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Second Highest Negative Difference: July 20 at 1600 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-33: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Negative Difference)

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Third Highest Negative Difference: July 20 at 1400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-34: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Negative Difference)

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Fourth Highest Negative Difference: July 17 at 1100 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-35: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Negative Difference)

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Fifth Highest Negative Difference: July 20 at 1300 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-36: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Negative Difference)

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Sixth Highest Negative Difference: July 17 at 1200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-37: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Negative Difference)

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Seventh Highest Negative Difference: July 20 at 1200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-38: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Seventh Highest Negative Difference)

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Eighth Highest Negative Difference: July 19 at 1000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-39: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Negative Difference)

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Ninth Highest Negative Difference: July 17 at 1000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-40: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Negative Difference)

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Tenth Highest Negative Difference: July 19 at 900 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-41: Comparison of PM2.5 Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Negative Difference)

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Figure 4-42: Scatterplot Comparing 24-hour Average Predicted PM2.5 Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations Performed by VISTAS (Alpine).

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4.3 Sulfate
Sulfate results for the top 10 positive and negative hours are presented in tabular format
in Table 4-3. The maximum positive difference is 5.76 µg/m3 falling to 3.43 µg/m3 for the 10th
high. The maximum negative difference is -4.57 µg/m3 falling to -2.34 µg/m3 for the 10th high.
The maximum positive percent difference on these days is 94.5% and negative percent difference
of -32.7%.
As expected, the maximum impacts on the top 10 positive and negative hours are
occurring very near the border. As was described in Section 2, the two CAMx simulations used
the same input data, except that the pollutant concentrations on in-flow boundary cells. For the
simulation on the VISTAS12 domain the in-flow concentrations are specified in hourly boundary
conditions extracted from the 12US2 simulation. For the 12US2 simulation the in-flow
concentrations were continuously updated from the cells outside the VISTAS12 domain. It
would be expected that concentration differences would occur from the differences in hourly
average concentrations, versus in the instantaneous concentrations. The top 10 positive
difference hours are presented in Figures 4-43 through 4-52 and the top 10 negative difference
hours are presented in Tables 4-53 through 4-62. The peak differences are occurring between
July 17 and July 20. The area of the peak impact is very near the northern border, north of
Minnesota.
Scatterplots of the daily average sulfate concentrations in local standard time at the
IMPROVE monitors are presented in Figure 4-63. The 12US2 results are plotted on the x-axis
and the VISTAS12 results are plotted on the y-axis. The data has a high degree of correlation
with a line of best fit with a slope of 1.0019, an intercept of 0.0008 µg/m3 and an R2 of 0.9999.
Examination of the difference animations often show differences along the boundary
becoming lower as the plumes along the boundary move into the domain.

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Table 4-3. Comparison of 2028elv3 CAMx 6.40 VISTAS12 and 12US2 Simulation of
Sulfate Concentrations (µg/m3). Hours with the top 10 maximum positive and maximum
negative differences are shown.
Year Month Day Hour VISTAS12
Conc.
12US2
Conc.
Difference
(µg/m3)
Percent
Difference Column Row
Maximum Positive
2011 7 21 4 13.56 7.80 5.76 73.9% 104 241
2011 7 20 14 25.43 20.65 4.79 23.2% 107 241
2011 7 21 3 44.72 40.44 4.28 10.6% 104 241
2011 7 20 15 13.32 9.20 4.12 44.8% 107 241
2011 7 21 1 31.50 27.50 4.00 14.5% 104 241
2011 7 20 12 45.82 41.92 3.90 9.3% 107 241
2011 7 20 11 39.79 35.92 3.87 10.8% 107 241
2011 7 21 0 10.21 6.66 3.55 53.2% 103 241
2011 7 20 23 7.17 3.69 3.48 94.5% 102 241
2011 7 20 22 8.31 4.88 3.43 70.3% 102 241
Maximum Negative
2011 7 20 14 73.45 78.03 -4.57 -5.9% 106 241
2011 7 20 15 66.90 71.41 -4.51 -6.3% 105 241
2011 7 20 13 88.61 92.84 -4.23 -4.6% 106 241
2011 7 20 16 54.97 59.00 -4.03 -6.8% 105 241
2011 7 20 12 112.23 116.24 -4.00 -3.4% 106 241
2011 7 17 11 6.88 10.22 -3.34 -32.7% 89 241
2011 7 17 12 6.87 9.91 -3.04 -30.7% 89 241
2011 7 19 10 11.25 14.18 -2.93 -20.6% 104 241
2011 7 17 10 5.80 8.59 -2.79 -32.5% 89 241
2011 7 19 9 11.52 13.86 -2.34 -16.9% 103 241

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Maximum Positive Difference: July 21 at 400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-43: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Positive Difference)

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Second Highest Positive Difference: July 20 at 1400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-44: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Positive Difference)

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Third Highest Positive Difference: July 21 at 300 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-45: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Positive Difference)

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Fourth Highest Positive Difference: July 20 at 1500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-46: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Positive Difference)

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Fifth Highest Positive Difference: July 21 at 100 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-47: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Positive Difference)

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Sixth Highest Positive Difference: July 20 at 1200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-48: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Positive Difference)

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Seventh Highest Positive Difference: July 20 at 1100 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-49: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations

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Eighth Highest Positive Difference: July 21 at 0000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-50: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Positive Difference)

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Ninth Highest Positive Difference: July 20 at 2300 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-51: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Positive Difference)

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Tenth Highest Positive Difference: July 20 at 2200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-52: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Positive Difference)

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Maximum Negative Difference: July 20 at 1400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-53: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Negative Difference)

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Second Highest Negative Difference: July 20 at 1500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-54: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Negative Difference)

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Third Highest Negative Difference: July 20 at 1300 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-55: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Negative Difference)

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Fourth Highest Negative Difference: July 20 at 1600 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-56: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Negative Difference)

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Fifth Highest Negative Difference: July 20 at 1200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-57: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Negative Difference)

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Sixth Highest Negative Difference: July 17 at 1100 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-58: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Negative Difference)

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Seventh Highest Negative Difference: July 17 at 1200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-59: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Seventh Highest Negative Difference)

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Eighth Highest Negative Difference: July 19 at 1000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-60: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Negative Difference)

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Ninth Highest Negative Difference: July 17 at 1000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-61: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Negative Difference)

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Tenth Highest Negative Difference: July 19 at 900 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-62: Comparison of Sulfate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Negative Difference)

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Figure 4-63: Scatterplot Comparing 24-hour Average Predicted Sulfate Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations Performed by VISTAS (Alpine).

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4.4 Nitrate
Nitrate results for the top 10 positive and negative hours are presented in tabular format
in Table 4-4. The maximum positive difference is 7.21 µg/m3 falling to 4.22 µg/m3 for the 10th
high. The maximum negative difference is -4.63 µg/m3 falling to -2.96 µg/m3 for the 10th high.
The maximum positive percent difference from these days is 130.1% and negative percent
difference of -49.2%.
As expected, the maximum impacts on the top 10 positive and negative hours are
occurring very near the border. As was described in Section 2, the two CAMx simulations used
the same input data, except that the pollutant concentrations on in-flow boundary cells. For the
simulation on the VISTAS12 domain the in-flow concentrations are specified in hourly boundary
conditions extracted from the 12US2 simulation. For the 12US2 simulation the in-flow
concentrations were continuously updated from the cells outside the VISTAS12 domain. It
would be expected that concentration differences would occur from the differences in hourly
average concentrations, versus in the instantaneous concentrations.
The top 10 positive difference hours are presented in Figures 4-64 through 4-73 and the
top 10 negative difference hours are presented in Figures 4-74 through 4-83. The peak
differences are generally occurring on January 3, July 17 and July 20. On January 3 the area of
the difference is generally in the north western portion of the domain in an area of a plume
entering the domain from Canada. On July 20 the differences are along the northern border,
north of Minnesota.
Scatterplots of the daily average nitrate concentrations in local standard time at the
IMPROVE monitors are presented in Figure 4-83. The 12US2 results are plotted on the x-axis
and the VISTAS12 results are plotted on the y-axis. The data has a high degree of correlation
with a line of best fit with a slope of 0.9996, an intercept of 0.0006 µg/m3 and an R2 of 1.0000.
Examination of the difference animations often show differences along the boundary
becoming lower as the plumes along the boundary move into the domain.

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Table 4-4. Comparison of 2028elv3 CAMx 6.40 VISTAS12 and 12US2 Simulation of
Nitrate Concentrations (µg/m3). Hours with the top 10 maximum positive and maximum
negative differences are shown.
Year Month Day Hour VISTAS12
Conc.
12US2
Conc.
Difference
(µg/m3)
Percent
Difference Column Row
Maximum Positive
2011 1 3 7 26.59 19.38 7.21 37.2% 32 235
2011 1 3 6 26.46 19.29 7.16 37.1% 32 235
2011 1 3 5 26.34 19.24 7.10 36.9% 32 235
2011 7 20 20 10.58 4.60 5.98 130.1% 99 241
2011 1 3 10 27.68 21.79 5.89 27.0% 33 235
2011 1 3 8 26.83 21.02 5.81 27.6% 32 235
2011 7 20 15 25.48 20.00 5.47 27.4% 107 241
2011 1 3 4 26.62 21.41 5.21 24.3% 32 235
2011 1 3 12 20.45 15.87 4.59 28.9% 16 241
2011 7 20 19 14.19 9.98 4.22 42.3% 99 241
Maximum Negative
2011 1 3 8 18.88 23.51 -4.63 -19.7% 33 233
2011 7 17 15 4.64 9.14 -4.49 -49.2% 90 241
2011 1 3 7 18.28 22.49 -4.21 -18.7% 33 233
2011 7 17 14 9.10 13.25 -4.15 -31.3% 90 241
2011 1 27 10 3.73 7.31 -3.58 -49.0% 224 241
2011 1 3 10 24.33 27.81 -3.48 -12.5% 30 233
2011 1 3 12 16.46 19.80 -3.33 -16.8% 13 240
2011 1 27 11 3.62 6.74 -3.12 -46.3% 224 241
2011 1 3 9 21.84 24.86 -3.02 -12.2% 33 234
2011 7 17 16 2.29 5.25 -2.96 -56.4% 91 241

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Maximum Positive Difference: January 3 at 700 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-64: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Positive Difference)

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Second Highest Positive Difference: January 3 at 600 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-65: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Positive Difference)

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Third Highest Positive Difference: January 3 at 500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-66: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Positive Difference)

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Fourth Highest Positive Difference: July 20 at 2000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-67: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Positive Difference)

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Fifth Highest Positive Difference: January 3 at 1000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-68: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Positive Difference)

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Sixth Highest Positive Difference: January 3 at 800 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-69: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Positive Difference)

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Seventh Highest Positive Difference: July 20 at 1500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-70: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Seventh Highest Positive Difference)

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Eighth Highest Positive Difference: January 3 at 400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-71: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Positive Difference)

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Ninth Highest Positive Difference: January 3 at 1200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-72: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Positive Difference)

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Tenth Highest Positive Difference: July 20 at 1900 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-73: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Positive Difference)

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Maximum Negative Difference: January 3 at 800 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-74: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Maximum Negative Difference)

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Second Highest Negative Difference: July 17 at 1500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-75: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Second Highest Negative Difference)

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Third Highest Negative Difference: January 3 at 700 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-76: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Third Highest Negative Difference)

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Fourth Highest Negative Difference: July 17 at 1400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-77: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fourth Highest Negative Difference)

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Fifth Highest Negative Difference: January 27 at 1000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-78: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Fifth Highest Negative Difference)

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Sixth Highest Negative Difference: January 3 at 1000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-79: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Sixth Highest Negative Difference)

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Seventh Highest Negative Difference: January 3 at 1200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-80: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Seventh Highest Negative Difference)

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Eighth Highest Negative Difference: January 27 at 1100 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-81: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Eighth Highest Negative Difference)

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Ninth Highest Negative Difference: January 3 at 900 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-82: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Ninth Highest Negative Difference)

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Tenth Highest Negative Difference: July 17 at 1600 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-83: Comparison of Nitrate Concentrations (µg/m3) for CAMx 6.40 on VISTAS12
and 12US2 Domains 2028elv3 Simulations (Tenth Highest Negative Difference)

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Figure 4-84: Scatterplot Comparing 24-hour Average Predicted Nitrate Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.40 on VISTAS12 and
12US2 Domains 2028elv3 Simulations Performed by VISTAS (Alpine).

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4.5 Organic Matter (OM)
Organic Matter (OM) results for the top 10 positive and negative hours are presented in
tabular format in Table 4-5. The maximum positive difference is 296.00 µg/m3 falling to 161.83
µg/m3 for the 10th high. The maximum negative difference is -228.07 µg/m3 falling to -134.62
µg/m3 for the 10th high. The maximum positive percent difference from these days is 97.4% and
negative percent difference of -33.7%.
As expected, the maximum impacts on the top 10 positive and negative hours are
occurring very near the border. As was described in Section 2, the two CAMx simulations used
the same input data, except that the pollutant concentrations on in-flow boundary cells. For the
simulation on the VISTAS12 domain the in-flow concentrations are specified in hourly boundary
conditions extracted from the 12US2 simulation. For the 12US2 simulation the in-flow
concentrations were continuously updated from the cells outside the VISTAS12 domain. It
would be expected that concentration differences would occur from the differences in hourly
average concentrations, versus in the instantaneous concentrations.
The top 10 positive difference hours are presented in Figures 4-85 through 4-94 and the
top 10 negative impact hours are presented in Tables 4-95 through 4-104. As with sulfate, the
peak differences are occurring between July 17 and July 20. The area of the peak impact is very
near the northern border, north of Minnesota. This is an area where CAMx simulations are
showing very high OC concentrations in an area heavily influenced by boundary conditions.
Scatterplots of the daily average OM concentrations in local standard time at the
IMPROVE monitors are presented in Figure 4-105. The 12US2 results are plotted on the x-axis
and the VISTAS12 results are plotted on the y-axis. The data has a high degree of correlation
with a line of best fit with a slope of 1.0004, an intercept of 0.0017 µg/m3 and an R2 of 1.0000.

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Table 4-5. Comparison of 2028elv3 CAMx 6.40 VISTAS12 and 12US2 Simulation of
Organic Matter Concentrations (µg/m3). Hours with the top 10 maximum positive and
maximum negative differences are shown.
Year Month Day Hour VISTAS12
Conc.
12US2
Conc.
Difference
(µg/m3)
Percent
Difference Column Row
Maximum Positive
2011 7 21 4 735.71 439.71 296.00 67.3% 104 241
2011 7 20 14 1262.44 1025.84 236.60 23.1% 107 241
2011 7 20 15 633.93 422.81 211.12 49.9% 107 241
2011 7 20 11 2118.91 1910.65 208.27 10.9% 107 241
2011 7 21 3 2457.80 2255.25 202.56 9.0% 104 241
2011 7 21 1 1835.92 1635.03 200.90 12.3% 104 241
2011 7 20 12 2332.91 2150.04 182.88 8.5% 107 241
2011 7 20 23 352.04 178.32 173.73 97.4% 102 241
2011 7 21 0 568.80 396.74 172.07 43.4% 103 241
2011 7 20 9 5412.29 5250.46 161.83 3.1% 105 241
Maximum Negative
2011 7 20 15 3744.14 3972.21 -228.07 -5.7% 105 241
2011 7 20 16 3083.95 3285.59 -201.64 -6.1% 105 241
2011 7 20 14 3985.64 4186.45 -200.81 -4.8% 106 241
2011 7 17 11 396.17 591.55 -195.38 -33.0% 89 241
2011 7 20 13 4751.92 4939.42 -187.49 -3.8% 106 241
2011 7 17 12 386.67 562.26 -175.59 -31.2% 89 241
2011 7 20 12 5973.55 6146.67 -173.11 -2.8% 106 241
2011 7 19 10 634.35 802.35 -168.00 -20.9% 104 241
2011 7 17 10 335.13 501.78 -166.65 -33.2% 89 241
2011 7 17 9 265.14 399.76 -134.62 -33.7% 89 241

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Maximum Positive Difference: July 21 at 400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-85: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Maximum Positive Difference)

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Second Highest Positive Difference: July 20 at 1400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-86: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Second Highest Positive Difference)

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Third Highest Positive Difference: July 20 at 1500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-87: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Third Highest Positive Difference)

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Fourth Highest Positive Difference: July 20 at 1100 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-88: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Fourth Highest Positive Difference)

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Fifth Highest Positive Difference: July 21 at 300 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-89: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Fifth Highest Positive Difference)

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Sixth Highest Positive Difference: July 21 at 100 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-90: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Sixth Highest Positive Difference)

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Seventh Highest Positive Difference: July 20 at 1200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-91: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Seventh Highest Positive Difference)

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Eighth Highest Positive Difference: July 20 at 2300 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-92: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Eighth Highest Positive Difference)

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Ninth Highest Positive Difference: July 21 at 0000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-93: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Ninth Highest Positive Difference)

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Tenth Highest Positive Difference: July 20 at 900 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-94: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Tenth Highest Positive Difference)

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Maximum Negative Difference: July 20 at 1500 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-95: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Maximum Negative Difference)

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Second Highest Negative Difference: July 20 at 1600 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-96: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Second Highest Negative Difference)

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Third Highest Negative Difference: July 20 at 1400 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-97: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Third Highest Negative Difference)

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Fourth Highest Negative Difference: July 17 at 1100 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-98: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Fourth Highest Negative Difference)

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Fifth Highest Negative Difference: July 20 at 1300 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-99: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Fifth Highest Negative Difference)

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Sixth Highest Negative Difference: July 17 at 1200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-100: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Sixth Highest Negative Difference)

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Seventh Highest Negative Difference: July 20 at 1200 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-101: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Seventh Highest Negative
Difference)

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Eighth Highest Negative Difference: July 19 at 1000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-102: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Eighth Highest Negative Difference)

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Ninth Highest Negative Difference: July 17 at 1000 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-103: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Ninth Highest Negative Difference)

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Tenth Highest Negative Difference: July 17 at 900 hours
VISTAS12
Difference (VISTAS12 - 12US2)

Figure 4-104: Comparison of Organic Matter Concentrations (µg/m3) for CAMx 6.40 on
VISTAS12 and 12US2 Domains 2028elv3 Simulations (Tenth Highest Negative Difference)

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Figure 4-105: Scatterplot Comparing 24-hour Average Predicted Organic Matter
Concentrations (µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.40
on VISTAS12 and 12US2 Domains 2028elv3 Simulations Performed by VISTAS (Alpine).

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5.0 CONCLUSIONS
A comparison has been made between CAMx 6.40 simulations using EPA’s 2028el
modeling platform as performed on the Alpine Geophysics computer system for the VISTAS12
and EPA continental US 12km (12US2) grid. The comparison was conducted for ozone, PM2.5,
sulfate, nitrate and organic carbon and included an examination both of hourly gridded
concentrations and at daily average concentrations at the IMPROVE monitors. The hourly
gridded comparison showed areas of maximum differences along the border with the differences
decreasing with distance into the VISTAS12 domain.
Two issues have been identified that have noted impact on the use of the VISTAS12
domain relative to the 12US2 domain. The first, and likely the most significant issue is a
time-step difference at the boundary where concentration conditions from outside of the domain
are injected into the modeling domain at one hour intervals compared to the model generated
(sub-hourly) time-step interval within the modeling domain. These differences can create initial,
significant concentration gradients along the boundary that can be carried through the episode
and transported to grid cells within the modeling domain. The second issue is related to the time
step in the model. The time step is determined by the maximum wind in the modeling domain. If
the highest wind in the 12US2 domain occurs somewhere outside the VISTAS12 domain, the
time step in the 12US2 simulation will be longer than in the VISTAS12 domain.
We note that in modeling the VISTAS12 domain with 12US2 boundary conditions, both
of these issues are exacerbated in the modeling due to large emission sources located near the
boundary of the 12US2/VISTAS12 boundary. A comparison of the daily average concentrations
at the IMPROVE monitors showed very small differences with an R2 of no less than 0.9999 for
all pollutants.
Alpine Geophysics does not see any features in the modeling that would preclude the use
of the VISTAS12 modeling domain for use in the VISTAS air quality planning, yet recognizes
the impacts related to the current configuration of the VISTAS12 domain and issues related to
border grid cells. While the analysis at the IMPROVE monitors has shown that the impact is
negligible at the IMPROVE monitors, if these differences are unacceptable to SESARM,
SESARM should consider using the 12US2 domain for regional haze modeling.