773 San Marin Drive, Suite 2115, Novato, CA 94998 415.899.0700 

### Draft Final Report

MODEL PERFORMANCE EVALUATON FOR THE

JUNE-JULY 2006 OZONE EPISODE FOR THE

DENVER 8-HOUR OZONE STATE IMPLEMENTATION PLAN

Prepared for:

Regional Air Quality Council 1445 Market Street, Suite 260 Denver, Colorado 80202

Prepared by:

Ralph Morris

Ed Tai Tanarit Sakulyanontvittaya ENVIRON International Corporation

773 San Marin Dr. Suite 2115 Novato, CA 94998

Dennis McNally

Cyndi Loomis Alpine Geophysics, LLC 7341 Poppy Way Arvada, Colorado 80007

August 29, 2008F:\Denver_O3_2008\Reports\2006_Base_Case\D raft_Final\TOC.doc August, 2008 

### i TABLE OF CONTENTS

Page

EXECUTIVE SU MARY ........................................................................................................ ES-1

Overview of Approach.........................................................................................................ES -1

Model Performance Evaluation ...........................................................................................ES-1

Conclusions of Model Performance Evaluation ................................................................ES-10

1. INTRODUCTION................................................................................................................ 1-1

1 .1 Background................................................................................................................ 1 -1 1.2 Purpose................................................................................................................... .... 1-2 1.3 Overview of Modeling Approach .............................................................................. 1-2 1.4 Emissions Modeling Approach.................................................................................. 1-5

2. OZONE OPERATIONAL MODEL PE RFORMACE EVALUATION ........................ 2-1

2.1 Introduction.............................................................................................................. .. 2-1

2.2 Overview of Model Perfor mance Evaluation Approach ........................................... 2-6 2.3 Operational Ozone Model Performance for the June-July 2006 Modeling Period ............................................................................... 2-7 2.4. Detailed Performance for Three 3-Day Episodes .................................................... 2-18 2.5 Ozone Operational Model Performance Evaluation Conclusions ........................... 2-54

3. DIAGNOSTIC MODEL PERF ORMANCE EVALUATION......................................... 3-1

3.1 Introduction.............................................................................................................. .. 3-1

3.2 Ozone Precursor Model Performance........................................................................ 3-1

3.3 Ozone Model Performance Aloft............................................................................. 3-26

3.4 PM Model Performance Evaluation......................................................................... 3-30 3.5 Diagnostic Model Performance Conclusions........................................................... 3-36

4. REFERENCES.................................................................................................................. ... 4-1

APPENDICES

Appendix A: Comparison of Predicted and Observed Spatial Distributions of the Daily

Maximum 8-Hour Ozone Concentrations in the Denver Area during June-July 2006 for the Final CAMx 2006 Base Case (Run 17) SimulationF:\Denver_O3_2008\Reports\2006_Base_Case\D raft_Final\TOC.doc August, 2008 

### ii TABLES

Table ES-1. Percent of the monito r-days that the model predicted daily maximum 8-hour ozone concentrations near the

monitor is within ±20% of the obser ved value (total monitor-days = 1008).....ES-3

Table 1-1. Lambert Conformal Pr ojection (LCP) definition for the Denver 36/12/4 km modeling grids ..................................................................... 1-4 Table 1-2. Grid definitions for MM5, Em issions and CAMx modeling domains ................ 1-4 Table 1-3. Summary of SM OKE configuration parameters and data inputs. ....................... 1-7

Table 1-4. 2006 emissions of all criteria pollutants by county for

O&G emissions in the D-J Basin....................................................................... 1-14 Table 1-5. Summary of CONCEPT parameters and data inputs......................................... 1-15 Table 1-6. Annual county-level total av erage weekday VMT from the TDM.................... 1-19 Table 1-7. BPR speed adjustment coefficien ts used in estimating congested speeds......... 1-20 Table 1-8. FHWA Roadway functional classification ........................................................ 1-21

Table 1-9. Vehicle classifications ....................................................................................... 1-21

Table 1-10. Fractional Allocation of FHWA Vehicle Classes to

MOBILE5 Vehicle Classes................................................................................ 1-21 Table 2-1. Ozone monitors operating within and near the DMA during 2002-2007................................................................................................. 2-3 Table 2-2. EPA’s 1-hour ozone performance goals (EPA, 1991)......................................... 2-4 Table 2-3. 8-hour ozone model performance goal comparing observed daily maximum 8-hour ozone concentrations with predicted values “near the monitor” (EPA, 1999). ...................................... 2-5 Table 2-4. Model performance goals and criteria for components of fine particle mass............................................................................................. 2-5

Table 2-5. Definitions of statistical performance measures used in the

model evaluation.................................................................................................. 2-6

Table 2-6. Percent of the monitor-d ays that the model predicted daily

maximum 8-hour ozone concen trations near th e monitor is

within ±20% of the observed value (total monitor-days = 1008) ...................... 2-16

Table 2-7. Final CAMx Run 17 2006 base case simulation daily 1-hour and 8-hour statistical performan ce measures for the June 17-19, 2006 episode and comparison with EPA performance goals...................................... 2-19

Table 2-8. Final CAMx Run 17 2006 base case simulation daily 1-hour and 8-hour statistical performan ce measures for the July 13-15, 2006 episode and comparison with EPA performance goals...................................... 2-29

Table 2-9. Final CAMx Run 17 2006 base case simulation daily 1-hour and 8-hour statistical performan ce measures for the July 27-29, 2006 episode and comparison with EPA performance goals...................................... 2-41

Table 3-1a. Locations of monito ring sites where VOC samples were collected during the summer of 2006.......................................................... 3-7 Table 3-1b. Sampling schedule and times for summer of 2006 VOC sampling study in the DMA................................................................................. 3-7 Table 3-2. Comparison of predicte d and observed morning CB05-VOC/NOx ratios at the downtown Denver CAMP monitoring site..................................... 3-10 Table 3-3. Comparison of pr edicted and observed morning paraffin (PAR) and ethane (ETHA) concentrations at the Weld County monitoring sites ........................................................................... 3-24F:\Denver_O3_2008\Reports\2006_Base_Case\D raft_Final\TOC.doc August, 2008 

### iii FIGURES

Figure ES-1. Hourly ozone performan ce statistics for June (left) and July (right) 2006 and Unpair ed Peak Accuracy (top), Mean Normalized Bias (middle) and Mean Normalized Gross Error (bottom) and co mparison against EPA’s model performance goals (red lines).............................................................................ES-3 Figure ES-2. Comparison of predic ted and observed daily maximum

8-hour ozone concentrations for the June-July 2006 modeling period and the final CAMx Run 17 2006 base case simulation using the Co-Located predicted value near the monitor ....................................ES-4 Figure ES-3. Comparison of the pred icted and observed daily maximum

8-hour ozone concentrations on the two highest observed ozone days during the June -July 2006 modeling period using

the final 2006 base case CA Mx simulation (Run 17) results.............................ES-5 Figure ES-4. Predicted and observed hour ly ozone concentrations at the Rocky Flats North (left) and Fo rt Collins West (eight) monitoring sites during July 13-16, 2006 (top) and July 27-29, 2006 (bottom) periods.................................................................................................ES-6 Figure ES-5. Comparison of predic ted and observed early morning (5-8am MST) VOC, NOx and CO concentrations and

VOC/NOx and CO/NOx ratios at the CAMP monitoring in

downtown Denver..............................................................................................ES-8 Figure ES-6. Comparison of predicted a nd observed vertical ozone profiles at Boulder for June 15 and July 21, 2006. .........................................................ES-9 Figure ES-7. Comparison of predicted and observed total PM 2.5 

### mass model performance at FR M (left) and IMPROVE (right) sites in the 12 km modeling domain ................................................................ES-10 Figure 1-1a. Nested 36/12/4 km mode ling domains for the Denver 8-hour ozone modeling study. Blue line domains are for CAMx/SMOKE

domains that are nested in the MM5 red line domains ........................................ 1-4 Figure 1-1b. Nested 12/4 km modeling domains for the Denver CAMx air quality and SMOKE emissions modeling............................................................ 1-5 Figure 1-2. D-J Basin boundaries overla id and 2006 oil and gas well locations.................... 1-9 Figure 1-3. 2006 NOx emissions by source category and by county in the D-J Basin...................................................................................... 1-12 Figure 1-4. 2006 VOC emissions by source category and by county in the D-J Basin...................................................................................... 1-13 Figure 1-5. D-J Basin NOx emissi ons proportional contributions by source category ............................................................................................. 1-13 Figure 1-6. D-J Basin VOC emissi ons proportional contributions by source category ............................................................................................. 1-14 Figure 1-7. DRCOG link-based tran sportation network used in the CONCEPT on-road mobile source emissions modeling ................................... 1-17 Figure 1-8. Monthly temporal profiles for facility classes 1 through 14.............................. 1-23 Figure 1-9. Day of week temporal profiles for June and July .............................................. 1-24F:\Denver_O3_2008\Reports\2006_Base_Case\D raft_Final\TOC.doc August, 2008 

### iv Figure 1-10. Hourly temporal prof iles for urban interstates for a week in June and July ..................................................................................... 1-24 Figure 1-11. Vehicle mix hourly profile for rural interstates in July...................................... 1-25 Figure 1-12. Vehicle mix hourly profile for urban interstates in July.................................... 1-25 Figure 2-1. Location of ozone mon itoring sites within and near the Denver Metropolitan Area (DMA) (triangle symbols point to monitor identifier)................................................................................... 2-3 Figure 2-2. Maximum daily maximum 8-hour ozone concentration (ppb) observed during the June-July 2006 episode and three “mini episodes” selected for more detailed analysis: June17-19, July 13-15, and July 27-29. ............................................................... 2-7 Figure 2-3a. Daily ozone model perf ormance evaluation statistical performance measures in the Denver NAA and comparison with EPA performance goals for June 2006, the final CAMx

Run17 2006 base case simulation and 1-hour ozone........................................... 2-9 Figure 2-3b. Daily ozone model performan ce evaluation statistical performance measures in the Denver NAA and comparison with EPA performance goals for July 2006, the final CAMx Run17 2006 base case simulation

and 1-hour ozone................................................................................................ 2-10 Figure 2-4a. Daily ozone model performan ce evaluation statistical performance measures in the Denver NAA and comparison with EPA performance goals for June 2006, the final CAMx Run17 2006 base case simulation

and 8-hour ozone................................................................................................ 2-12 Figure 2-4b. Daily ozone model performan ce evaluation statistical performance measures in the Denver NAA and comparison with EPA performance goals for July 2006, the final CAMx Run17 2006 base case simulation

and 8-hour ozone................................................................................................ 2-13 Figure 2-5. Compared of observed highest daily maximum 8-hour ozone concentration for each day duri ng June (top) and July (bottom) 2006 with concurrent spatia lly paired prediction from the

CAMx Run 17 2006 base case simulation......................................................... 2-15 Figure 2-6a. Comparison of predicted a nd observed daily maximum 8-hour ozone

concentrations for the June-Jul y 2006 modeling period and the final CAMx Run 17 2006 base case simulation using the Maximum predicted value near the monitor........................................................................ 2-17 Figure 2-6b. Comparison of predicted and observed daily maximum 8-hour ozone

concentrations for the June-Jul y 2006 modeling period and the final CAMx Run 17 2006 base case simulation using the Closest predicted value near the monitor........................................................................ 2-17 Figure 2-6c. Comparison of predicted a nd observed daily maximum 8-hour ozone

concentrations for the June-Jul y 2006 modeling period and the final CAMx Run 17 2006 base case simulation using the

Co-Located predicted value near the monitor.................................................... 2-18 Figure 2-7a. Spatial distribution of the predicted and observed daily

maximum 8-hour ozone concen trations (ppb) in the Denver area on July 17, 2006 for the final CAMx Run 17 2006

base case simulation........................................................................................... 2-20F:\Denver_O3_2008\Reports\2006_Base_Case\D raft_Final\TOC.doc August, 2008 

### v Figure 2-7b. Spatial distribution of the predicted and observed daily

maximum 8-hour ozone concen trations (ppb) in the Denver area on July 18, 2006 for the final CAMx Run 17 2006

base case simulation........................................................................................... 2-21 Figure 2-7c. Spatial distribution of the predicted and observed daily maximum 8-hour oz one concentrations (ppb) in the Denver area on July 19, 2006 for the final CAMx

Run 17 2006 base case simulation..................................................................... 2-22 Figure 2-8. Time series of pr edicted and observed hourly ozone concentrations (ppb) during June 17-19, 2006 for the

final CAMx Run 17 2006 base case simulation................................................. 2-26 Figure 2-9a. Comparison of hourly NOx (top), CO (middle) and ozone (bottom) predicted and observed time series at the Welby monitoring site for June 17-19, 2006 and

the final CAMx Run17 2006 base case simulation............................................ 2-27 Figure 2-9b. Comparison of hourly NOx (top) and ozone (bottom) predicted and observed time series at the CAMP monitoring site for June 17-19, 2006 and the preliminary CAMx

Run17 2006 base case simulation...................................................................... 2-28 Figure 2-10a. Spatial distribution of the predicted and observed daily

maximum 8-hour ozone concen trations (ppb) in the Denver area on July 13, 2006 for the final CAMx Run 17 2006

base case simulation........................................................................................... 2-30 Figure 2-10b. Spatial distribution of the predicted and observed daily

maximum 8-hour ozone c oncentrations (ppb) in the Denver area on July 14, 2006 for the final CAMx

Run 17 2006 base case simulation..................................................................... 2-31 Figure 2-10c. Spatial distribution of the predicted and observed daily

maximum 8-hour ozone c oncentrations (ppb) in the Denver area on July 15, 2006 for the final CAMx

Run 17 2006 base case simulation..................................................................... 2-32 Figure 2-11. Hourly time series of predicted and observed hourly ozone concentrations for the July 13-15, 2006 period

and the final CAMx Run17 2006 base case simulation..................................... 2-38 Figure 2-12a. Comparison of hourly NOx (top) and ozone (bottom) predicted and observed time series at the Welby monitoring site for July 13-15, 2006 and the final CAMx Run17 2006

base case simulation base case simulation......................................................... 2-39 Figure 2-12b. Comparison of hourly NOx (top) and ozone (bottom) predicted and observed time series at the CAMP monitoring site for July 13-15, 2006 and the final CAMx Run17 2006

base case simulation base case simulation......................................................... 2-40 Figure 2-13a. Spatial distribution of the predicted and observed daily

maximum 8-hour ozone c oncentrations (ppb) in the Denver area on July 27, 2006 for the final CAMx

Run 17 2006 base case simulation..................................................................... 2-42F:\Denver_O3_2008\Reports\2006_Base_Case\D raft_Final\TOC.doc August, 2008 

### vi Figure 2-13b. Spatial distribution of the predicted and observed daily

maximum 8-hour ozone c oncentrations (ppb) in the Denver area on July 28, 2006 for the final CAMx

Run 17 2006 base case simulation..................................................................... 2-43 Figure 2-13c. Spatial distribution of the predicted and observed daily

maximum 8-hour ozone c oncentrations (ppb) in the Denver area on July 29, 2006 for the final CAMx

Run 17 2006 base case simulation..................................................................... 2-44 Figure 2-14a. Time series of predicted and observed hourly ozone concentrations (ppb) for the July 27-29, 2006 period, monitoring sites to the Northwest of downtown

Denver and the final CAMx Run17 2006 base case simulation ........................ 2-47 Figure 2-14b. Time series of pred icted and observed hourly ozone concentrations (ppb) for the July 27-29, 2006 period, monitoring sites mostly south of downtown Denver and

the final CAMx Run17 2006 base case simulation............................................ 2-49 Figure 2-14c. Time series of pr edicted and observed hourly ozone concentrations (ppb) for the July 27-29, 2006 period, monitoring sites to the North of downtown Denver and

the final CAMx Run17 2006 base case simulation............................................ 2-51 Figure 2-15a. Comparison of hourly NOx (top) and ozone (bottom) predicted and observed time series at the CAMP monitoring site for July 27-29, 2006 and the final CAMx Run17 2006

base case simulation........................................................................................... 2-52 Figure 2-15b. Comparison of hourly NOx (top) and ozone (bottom) predicted and observed time series at the Welby monitoring site for July 27-29, 2006 and the final CAMx Run17 2006

base case simulation........................................................................................... 2-53 Figure 3-1a. Daily model performance statistics for June 2006, hourly NOx concentrations in the DMA (CAMP and WELB)

and the final CAMX Run 17 2006 base case simulation..................................... 3-2 Figure 3-1b. Daily model performa nce statistics for July 2006, hourly NOx concentrations in the DMA (CAMP and WELB)

and the final CAMX Run 17 2006 base case simulation..................................... 3-3 Figure 3-2a. Daily model performance statistics for June 2006, hourly CO concentrations in the DMA (13 sites) and the final CAMX

Run 17 2006 base case simulation....................................................................... 3-4 Figure 3-2b. Daily model performance statistics for July 2006, hourly CO concentrations in the DMA (13 sites) and the final CAMX

Run 17 2006 base case simulation....................................................................... 3-5 Figure 3-3. Locations of monitori ng sites where VOC samples were collected during the summer of 2006................................................................... 3-6 Figure 3-4a. Comparison of predic ted and observed 3-hour average morning (5-8am MST) CB05-VOC, NOx and CO

concentrations at the CAMP monitor for the

CAMx Run 17 2006 base case simulation......................................................... 3-11F:\Denver_O3_2008\Reports\2006_Base_Case\D raft_Final\TOC.doc August, 2008 

### vii Figure 3-4b. Comparison of pr edicted and observed 3-hour average morning (5-8am MST) CB05-VOC/NOx and CO/NOx ratio and ethane (ETHA) concentrations

at the CAMP monitor for the CAMx Run 17 2006

base case simulation........................................................................................... 3-12 Figure 3-5a. Comparison of pr edicted and observed 3-hour average morning (5-8am MST) CB05-VOC, NOx and CO

concentrations at the WELB monitor for the CAMx

Run 17 2006 base case simulation..................................................................... 3-13 Figure 3-5b. Comparison of pr edicted and observed 3-hour average morning (5-8am MST) CB05-VOC/NOx and CO/NOx ratio and ethane (ETHA) concentrations at the Welby monitor for the CAMx Run 17 2006

base case simulation........................................................................................... 3-14 Figure 3-6. Comparison of the predicted and observed morning CB05-VOC concentrations at the Ft. Lupton and Platteville sites in Weld County......................................................................... 3-16 Figure 3-7. Comparison of the predicted and observed morning CB05-VOC concentrations at the Ft. Lupton and Platteville sites in Weld County......................................................................... 3-17 Figure 3-8a. omparison of pr edicted and observed 5-8am MST CB05 VOC species at th e CAMP monitor on June 19, 2006................... 3-19 Figure 3-8b. Comparison of pr edicted and observed 5-8am MST CB05 VOC species at th e CAMP monitor on July 13, 2006.................... 3-20 Figure 3-8c. Comparison of pr edicted and observed 5-8am MST CB05 VOC species at th e CAMP monitor on July 28, 2006.................. 3*-21 Figure 3-9a. Comparison of pr edicted and observed 5-8am MST CB05 VOC species at the Welby monitor on June 19, 2006.................... 3-22 Figure 3-9b. Comparison of pr edicted and observed 5-8am MST CB05 VOC species at th e Welby monitor on July 13, 2006 .................... 3-23 Figure 3-10. Comparison of predicted and observed CB05 VOC species at the Ft. Lupton monitoring site........................................................... 3-25 Figure 3-11a. Comparison of pred icted and observed vertical distribution of ozone concentrations on June 15, 2006

for the CAMx Run 17 2006 base case simulation. ............................................ 3-27 Figure 3-11b. Comparison of predicted and observed vertical distribution of ozone concentrations on June 23, 2006 for the

CAMx Run 17 2006 base case simulation......................................................... 3-28 Figure 3-11c. Comparison of predicted and observed vertical distribution of ozone concentrations on June 29, 2006 for the

CAMx Run 17 2006 base case simulation......................................................... 3-28 Figure 3-11d. Comparison of predicted and observed vertical distribution of ozone concentrations on July 14, 2006 for the

CAMx Run 17 2006 base case simulation......................................................... 3-29 Figure 3-11e. Comparison of predicted and observed vertical distribution of ozone concentrations on July 21, 2006 for the

CAMx Run 17 2006 base case simulation......................................................... 3-29F:\Denver_O3_2008\Reports\2006_Base_Case\D raft_Final\TOC.doc August, 2008 

### viii Figure 3-11f. Comparison of predicted and observed vertical distribution of ozone concentrations on July 26, 2006 for the

CAMx Run 17 2006 base case simulation......................................................... 3-29 Figure 3-12. Comparison of predicted and observed total PM 2.5 

### mass model performance at FRM (left) and IMPROVE (right)

sites in the 12 km modeling domain .................................................................. 3-32 Figure 3-13. Comparison of predicted and observed total sulfate (SO4) model performance at CASTNET (top left), IMPROVE (top right), STN (botto m left) and NADP (bottom right) monitoring sites in th e 12 km modeling domain ............................................... 3-33 Figure 3-14. Comparison of predicted and observed total nitrate (NO3) model performance at CASTNET (top left), CASTNET for total NO3 (NO3+HNO3) (top right), IMPROVE (bottom left) and NADP (bottom right) monitoring sites in the 12 km modeling domain........................ 3-34 Figure 3-15. Comparison of predic ted and observed Organic Carbon (OC; top) and Elemental Carbon (EC; bottom) model performance at IMPROVE (l eft) and STN (right) monitoring

sites in the 12 km modeling domain .................................................................. 3-35F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Exec_Sum1.doc August 2008 

### ES-1 EXECUTIVE SUMMARY

Due to violations of the 0.08 parts per million (ppm) 8-hour ozone National Ambient Air Quality Standard (NAAQS) based on 2005-2007 air quali ty data, in November 2007 the Denver Metropolitan Area (DMA) reverted to an 8-hour ozone nonattainment area. This requires the DMA to develop an 8-hour ozone State Implemen tation Plan (SIP) that demonstrates the area will achieve the 0.08 ppm 8-hour ozone NAAQS by 2010. The Denver Regional Air Quality Council (RAQC), in consultation with the Colo rado Department of Health and Environment (CDPHE) Air Pollution Control Division (APCD) contracted with ENVIRON International Corporation and their subcontra ctor Alpine Geophysics, LLC to develop the photochemical modeling databases necessary to demonstrate that the DMA will achieve the 0.08 ppm 8-hour ozone NAAQS by 2010.

OVERVIEW OF APPROACH

The Comprehensive Air-quality Mo del with extensions (CAMx; www.camx.com ) was set up for a June-July 2006 episode on a 36/12/4 km grid with the 4 km domain focused on Colorado. Meteorological inputs were prepared using th e MM5 meteorological model whose results and evaluation are discussed by McNally and co-workers (2008). An initial emissions inventory was prepared using the SMOKE emissions modeling system and a preliminary 2006 base case was performed. A preliminary model performa nce evaluation was conducted and diagnostic sensitivity tests performed to identify an optimal model conf iguration for simulating ozone formation in the DMA (Morris et al., 2008b).

A revised CAMx 2006 base case (Run 17) simula tion was conducted that included the following emission updates from the preliminary 2006 base case simulation reported by Morris and coworkers (2008):

• Corrections and enhancements to the 2006 emissions for Colorado provided by the

CDPHE/APCD.

• Application ConCEPT MV mobile source emissions modeling system that uses diurnally varying link-based Vehicle Miles Traveled (V MT), fleet mix and other data to provide

more detailed on-road mobile source emissions in the DMA.

• Use of the WRAP Phase III oil and gas produc tion emissions inventory for the DenverJulesburg Basin.

• Biogenic emission estimates from the MEGAN biogenic emissions model (Guenther and Wiedinmyer, 2004).

This report presents the model performance ev aluation for the final 2006 base case simulation performed as part of the Denver 8-hour ozone attainment demonstration modeling.

MODEL PERFORMANCE EVALUATION

The model performance evaluation of the Denver final 2006 base case simulation performed both an operational evaluation that evaluate d how well the model predicted the ozoneF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Exec_Sum1.doc August 2008 

### ES-2 observations and a diagnostic ev aluation that evaluated the m odel for ozone precursors, key indicator species, particulate matter (PM) and ozone aloft.

Operational Model Performance Evaluation

The operational model performance evaluation focused on how well the model predicted the

observed surface ozone concentrations in the DM A and included graphical displays of model performance as well as statistic al evaluation metrics and compar isons with model performance goals.

Comparison against Model Performance Goals

One element of an ozone SIP model performan ce evaluation is to test how well the model reproduces the observed ozone concentrations. As part of this, statisti cal performance metrics are calculated that are compared against mode l performance goals as a method to gauge model performance, compare it against other studies and to assist in determining whether the model is getting the right answer. EPA’s latest modeling guidance (EPA, 2007) emphasizes using graphical and diagnostic evaluati on techniques to assure that the photochemical rid model is capturing the correct chemical regimes and emissi ons sources that lead to the high ozone (i.e., assuring that the model is getting the ri ght answer for the right reason).

EPA’s 1991 1-hour ozone guidance in cluded three performance goals that have been used for

over two decades to assist in ev aluating ozone models as part of the ozone SIP modeling process:

• Unpaired Accuracy of the Peak ≤ ±20%;

• Normalized Mean Bias ≤ ±15%; and

• Normalized Mean Gross Error ≤ 35%.

The Mean Normalized Bias and Gross Error statistical measures are calculated using all predicted and observed hourly ozone pairs matc hed by time and location for which the observed ozone is 60 ppb or greater.

Figure ES-1 compares the Denver final 2006 base case CAMx hourly ozone model performance against these three EPA model performance goals for each day during the June-July 2006 episode. The CAMx final 2006 base case simula tion achieves the Unpair ed Accuracy of the Peak performance goal of ≤ ±20% for 58 of the 60 simulation days of the episode (i.e., 97% of the modeled days). There are 58 days with bias and error comparisons du ring the episode as two days had no observed ozone greater than 60 ppb so no statistics could be calculated. Of these 58 days, 50 of them (86%) achieved EPA’s ≤ ±15% performance for Mean Normalized Bias and all of them achieves EPA’s performance goal for Mean Normalized Gross Error.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Exec_Sum1.doc August 2008 

### ES-3 Unpaired Peak Accuracy

-30 -20 -10

0 10 20 306/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

+20%

-20% Unpaired Peak Accuracy

-30 -20 -10

0 10 20 307/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

+20%

-20%

Normalized Bias

-30 -20 -10

0 10 20 306/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

+15%

-15% Normalized Bias

-30 -20 -10

0 10 20 307/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

+15%

-15%

Normalized Error

0 10 20 30 406/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

35% Normalized Error

0 10 20 30 407/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%)

Run17

35% 

### Figure ES-1. Hourly ozone performance statistics for June (left) and July (right) 2006 and Unpaired Peak Accuracy (top), Mean Normaliz ed Bias (middle) and Mean Normalized Gross Error (bottom) and comparison against EPA’s model performance goals (red lines).



### EPA’s draft 1999 8-hour ozone modeling guidance has a performance goal for daily maximum 8-hour ozone concentrations that the predicted va lue near the monitor be within ±20% on most monitor-days. This is a partic ularly important performance metr ic as it is these exactly same predicted daily maximum 8-hour ozone concentrati ons near the monitor that are used to make future year ozone projections. By “near the monito r” we used the same 7 x 7 array of 4 km grid

cells centered on the monitor as us ed in the ozone projections and have made this analysis three ways by selecting the Maximum predicted value in the array, the predicted value Closest to the observed value, and the predicted value Co-Located at the monitor, with this last comparison being a particularly stringent te st of model performance. Tabl e ES-1 summarizes the results of this performance test, with a scatter plot of the predicted and observed daily maximum 8-hour

ozone concentrations Co-Located at the monito r shown in Figure ES-2. Using the Maximum, Closest and Co-Located predicted daily maximu m 8-hour ozone concentration near the monitor

we see that the model achieves the within ±20% of the observed value performance goal 76%, 89% and 82% of the monitor-days. Thus, th e Denver final 2006 base case CAMx simulation (Run 17) daily maximum 8-hour ozone predictions achieves EPA’s ≤ ±20% of the observed value on most monitor-days performance goal.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Exec_Sum1.doc August 2008 

### ES-4 Table ES-1. Percent of the monitor-days that the model predicted daily maximum 8-hour ozone
concentrations near the monitor is within ±20% of the observed value (total monitor-days = 1008).

Maximum Near the Monitor Percent Difference # Days % Days

<-20 9 1%

-20% to +20 769 76%

> +20 230 23%

Closest Near the Monitor Percent Difference # days %

<-20 23 2%

-20% to +20 902 89%

> +20 83 8%

Co-Located At the Monitor Percent Difference # days %

<-20 48 5%

-20% to +20 829 82%

> +20 131 13%



### Daily maximum 8-Hour ozone at monitor. All sites & all days. Subregion = Denver June+July, 2006. Run17 04km

0 20 40 60 80 100 120

0 20 40 60 80 100 120

Observed Ozone (ppb)Predicted Ozone (ppb) 

### r 2 

### =0.2615

O - - O shows quantiles



### Figure ES-2. Comparison of predicted and observed daily maximum 8-hour ozone concentrations for the June-July 2006 modeling period and the final CAMx Run 17 2006 base case simulation using the Co-Located predicted value near the monitor.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Exec_Sum1.doc August 2008 

### ES-5 Spatial and Temporal Evaluation of Ozone Model Performance

A detailed analysis of the ozone model performa nce was assessed by examining the ability of the model to predict the observed ozone concentrations for three 3-day episodes during the June-July 2006 modeling period when 7 of the 9 8-hour ozone exceedance days occurred. The detailed ozone model performance revealed that at some days the model failed to reproduce the elevated ozone concentrations and model performance was poor. Whereas, on other days the ozone model performance was quite good. In general, th ere were days with good model performance at the high southern (e.g., Chatfiel d) and northwestern (e.g., Rocky Flats North) ozone monitors, but there was a general underprediction bias at the northern Fort Collins West monitor. Figure ES-3 compares the spatial distribution of th e predicted and observed daily maximum 8-hour ozone concentrations in the two highest days during the two month mode ling period: July 14 and 29, 2006. On July 14 th 

### , the model is correctly predicting el evated ozone concentrations to the north-northwest of the DMA with the highest mode led values near the highest observed value at Fort Collins West monitor, although the modeled peaks are below the observed ozone peaks. On July 29, 2006 the model correctly predicts that th e very highest ozone concentrations occur in

and near the DMA with both the modeled and obse rved 8-hour ozone peaks in excess of 90 ppb. Time series of predicted and observed hourly oz one concentrations for the July 13-16 and July 27-29 periods and the two highest monitoring s ites (RFNO and FTCW)are shown in Figure ES4. In general the model underestimates the obser ved ozone peaks; the ex ception to this is at Rocky Flats North monitor for July 27- 29, 2006 that exhibits very good ozone model performance.

Figure ES-3. Comparison of the predicted and observed daily maximum 8-hour ozone concentrations on the two highest observed ozone days during the June-July 2006 modeling period using the final 2006 base case CAMx simulation (Run 17) results.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Exec_Sum1.doc August 2008 

### ES-6 RFNO: Rocky Flats North -693.592 21.629

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6

DateO3 [ppb] Minimum to Maximum Range Observed Predicted FTCW: Fort Collins West -682.854 96.141

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6

DateO3 [ppb] Minimum to Maximum Range Observed Predicted

RFNO: Rocky Flats North -693.592 21.629

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6

DateO3 [ppb] Minimum to Maximum Range Observed Predicted FTCW: Fort Collins West -682.854 96.141

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6

DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure ES-4. Predicted and observed hourly ozone concentrations at the Rocky Flats North (left) and Fort Collins West (eight) monitoring sites during July 13-16, 2006 (top) and July 27-29, 2006 (bottom) periods.



### Diagnostic Model Performance Evaluation

In addition to the many diagnostic tests performed to test the sensitivity of the model to model inputs and options performed as part of the pr eliminary model performance evaluation discussed in previous reports (Morris et al., 2008b; McNally, et al ., 2008), the diagnostic model performance evaluation also included comparis ons against ozone precu rsors, key indicator species, PM species a nd ozone aloft.

Ozone Precursor and Indicator Species Comparisons

The CDPHE/APCD collected 3-hour VOC samples at several sites during a few days of the June-July 2006 modeling period. Figure ES-5 displays the example comparisons of ozone precursor and their ratios at the downtown Denver CAMP monitoring site. In these comparisons, the observed VOC species were converted to the CB05 lumped VOC species that is the chemical mechanism used in CAMx. Then the modeled and observed CB05 species were summed to get the total predicted and observed VOC concentrat ions, respectively. Note that ethane (ETHA) was not included in the total VOC species when summing the CB05 lumped species. Also note that since the VOC sampling did not collected m easurements for methanol and ethanol, those species were also not accounted for when summing the CB05 species.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Exec_Sum1.doc August 2008 

### ES-7 The model is systematically underpredicting th e observed VOC concentr ations at the CAMP monitoring site, whereas for NOx and CO there ar e days with underpredictions and days with overpredictions, although on average NOx is underp redicted as well. The CAMP monitor is located in downtown Denver where we would expect VOC, NOx and CO emissions to be dominated by on-road mobile sources. Thus, these comparisons provide a good evaluation of the on-road mobile source emissions. However, th ere are incommensurability differences between the observed point measurements at the 4 km grid cell average model predictions. Thus, a better indication of the accuracy of the on-road m obile source emissions are the VOC/NOx and CO/NOx key indicator ratio comparisons. Comp arison of the predicted and observed VOC/NOx ratios also provide an indicati on of whether the model is reproduc ing the correct chemical regime in the DMA. Of the 15 days with morning VOC/NOx comparisons, very good comparisons are seen on 11 (73%) of the days. Of the four da ys in which the model is underpredicting the observed VOC/NOx ratio one is July 4 th 

### that has atypical traffic patte rns that were not simulated in the CONCEPT modeling. Two of the othe r VOC/NOx ratio overprediction days were weekend days, although on two other weekend da ys we saw good performance. The CO/NOx ratios appear to be slightly overpredicted on most days which may indicate that MOBILE6 is overestimating the on-road mobile source CO emi ssions, which has also been noted by Pollack and co-workers (2004). Ethane (ETHA) is underpre dicted by approximately a factor of 10 at the

CAMP monitor with observed va lues of ~25 ppbC and predicte d values of ~2.5 ppbC. The underprediction of ethane is even greater at the two Weld County mon itoring sites where the CB05 paraffin species is also underpredicted. As et hane is primarily associated with natural gas, its underprediction could indicate that organic emissions from natural gas related and oil and gas development sources are unders tated in the inventory.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Exec_Sum1.doc August 2008 

### ES-8 Predicted vs. Observed VOC at CAMP

0.00 100.00 200.00 300.00 400.00606166061960622606256062860701607046070760710607136071660719607226072560728

DateVOC [ppbC] Predicted Observed Predicted vs. Observed VOC/NOx Ratio at CAMP

0 1 2 3 4 5606166061960622606256062860701607046070760710607136071660719607226072560728

DateVOC/NOx [ppbC/ppb] Predicted Observed

Predicted vs. Observed NOx at CAMP

0 50 100 150 200606166061960622606256062860701607046070760710607136071660719607226072560728

DateNOx [ppb] Predicted Observed Predicted vs. Observed CO/NOx Ratio at CAMP

0 5 10 15 20 25 30606166061960622606256062860701607046070760710607136071660719607226072560728

DateCO/NOx [ppb/ppb] Predicted Observed

Predicted vs. Observed CO at CAMP

0 200 400 600 800 1000 1200606166061960622606256062860701607046070760710607136071660719607226072560728

DateCO [ppb] Predicted Observed Predicted vs. Observed ETHA at CAMP

0 10 20 30 40 50 60606166061960622606256062860701607046070760710607136071660719607226072560728

DateETHA [ppbC] Predicted Observed



### Figure ES-5 . Comparison of predicted and observed early morning (5-8am MST) VOC, NOx and CO concentrations and VOC/NOx and CO/NOx ratios at the CAMP monitoring in

downtown Denver.



### In addition to the underestimation of observed ethane and paraffin VO C species noted above, carbonyl VOC species were also systemati cally underpredicted by the model. The underprediction of acetaldehyde may be due in pa rt to the SMOKE VOC speciation profile for on-road mobile sources not accounting for etha nol blended gasoline whose combustion produces higher acetaldehyde than conve ntional gasoline. However, the reasons for the large underprediction of formaldehyde are less clear and since formaldehyde is an important VOC species that initiates the radica l cycle its underprediction may he lp explain why the model tends to form ozone too slowly and does not obtain as high ozone peaks as obs erved. A review and evaluation of the VOC speciation profile s in the Denver modeling is recommended.

Ozone Aloft

During six days of the June-July 2006 mode ling period, ozonesondes were released from

Boulder that obtained a measured vertical ozon e profile in the atmosphere. One hypothesis for the conceptual model on ozone formation in the DMA is that on some days there is a reservoir of ozone above the ground that is entrained and mixe d to the ground as the mixing height rises. The comparison of the modeled vertical ozone pr ofile with the ozonesonde measurements would provide an indication of whethe r the model is capturi ng this phenomenon. As the ozonesonde

rises it will move downw ind with the prevailing wind. In these comparisons we used theF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Exec_Sum1.doc August 2008 

### ES-9 modeled vertical ozone profile in the grid cell at the time of the ozonesonde launch, so did not account for the horizontal and temporal displacem ent of the ozonesonde measurements from its launch point and start time. Figure ES-6 displays two of the comparisons of the predicted and observed vertical ozone profile s for June 15 and July 21, 2006. In general, the model does a better job reproducing the observed ve rtical ozone profiles for the three June da ys than the three July days. For example, on June 15 the model a nd observed ozone agree well in the lowest 2 km of the atmosphere and then deviate from each other. On the other hand, on July 21, 2006 the model is underpredicting the observed ozone in the lowest 2 km of the atmosphere by 20 ppb.

Predicted and Observed Ozonesonde over Boulder on June 15, 2006 at 12pm

0 1 2 3 4 5 6 7 8 9 10

0 50 100 150 200 250 300

Ozone [ppb]Height above Surface [km] Observed Predicted, Run17.1204 Predicted and Observed Ozonesonde over Boulder on July 21, 2006 at 11am MST

0 1 2 3 4 5 6 7 8 9 10

0 20 40 60 80 100

Ozone [ppb]Height above Surface [km] Observed Predicted Run17.1204



### Figure ES-6. Comparison of predicted and observed vertical ozone profiles at Boulder for June 15 and July 21, 2006.



### PM Performance

The Denver June-July 2006 photochemical modeling database was developed for demonstrating

attainment of the 8-hour ozone standard. C onsequently, the focus was on ozone and ozone precursor performance. Thus, no effort wa s spent on optimizing model performance for particulate matter (PM) species. In particular, the CDPHE/APCD only provided complete ozone precursor emissions (i.e., VOC, NOx and CO) fo r the state of Colorado. When modeling many sources categories, such as on-road mob ile using SMOKE-MOBILE6 and CONCEPT MV models and processing the CEM data for point s ources, we pick up the PM precursor emissions. However, for area and non-road mobile source emissions for sources in Colorado we only have ozone precursor emissions so are missing many PM related species (e.g., SO2, primary PM and ammonia). Thus, we expect to underpredict PM mass and PM species in the model performance

evaluation.

Figure ES-7 displays an exampl e evaluation for total PM2.5 mass from the more urban-oriented

FRM and more rural-oriented IMPROVE mon itoring networks. As expected, PM2.5 is underestimated most of the time. This underpredi ction is prevalent acros s all PM species with the lowest underprediction for SO4 and highest for NO3. These results are consistent with missing PM precursor emissions from area and non-road sources that would affect NO3 the

most.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Exec_Sum1.doc August 2008 

### ES-10 Figure ES-7. Comparison of predicted and observed total PM 2.5 

### mass model performance at FRM (left) and IMPROVE (right) sites in the 12 km modeling domain.



### CONCLUSIONS OF MODEL PERFORMANCE EVALUATION

As noted in EPA’s latest air quality modeling guidance, “by de finition, models are simplistic approximations of complex phenomena” that “...c ontain many elements that are uncertain”. Consequently, achieving perfect model performan ce is unattainable and some uncertainties will always exist. The Denver final 2006 base case (Run 17) CAMx simulation achieves EPA’s performance goals on a vast majority of days during the June-July 2006 modeling episode. The model is also exhibiting very good agreement for VOC/NOx ratios in Denver on most days, suggesting that the model is simulating the correc t chemical regimes. The model performance is as good as or better than past ozone SIP modeling in the Denver and many other areas whose SIPS have been approved by EPA. Based on the model performance evaluation presented in this report, we conclude that the model is performing well enough to reliable project future-year

ozone concentrations within the normal uncerta inties of photochemical grid modeling. Although care should be taken that the ozone projec tions are not unduly affected by the few poor performing days.

The model performance evaluation has identified se veral areas of future research that could improve model performance including a focus on VOC speciation and the presence of aldehydes in the inventory, improvements in oil and gas emi ssions and other sources of natural gas related

emission sources and better simulation of ozone aloft.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-1 1.0 INTRODUCTION

1.1 BACKGROUND

Ozone air quality in the Denve r Metropolitan Area (D MA) has been near the 8-hour ozone National Ambient Air Quality Standard (NAAQS) of 0.08 ppm (exceedance defined by values of 85 ppb or higher) for several years. Based on 2005-2007 measured air quality, the DMA violated the 0.08 ppm 8-hour ozon e NAAQS so is required to prepare an 8-hour ozone State Implementation Plan (SIP) that demonstrates a ttainment by 2010. This re port presents the 2006 base case modeling and model performance eval uation element of the DMA 2010 attainment demonstration modeling.

1.1.1 Denver EAC 8-Hour Ozone SIP

In December 2002, the Denver Regional Air Quality Council (RAQC) and Colorado Department of Health and Environment (CDPHE) Air Polluti on Control Division (APCD) and others entered into an 8-hour ozone Early Ac tion Compact (EAC) with the U.S. Environmental Protection Agency (EPA). EPA’s EAC allows an area to submit an enforceable 8-hour ozone State Implementation Plan (SIP) by March 2004 that demonstrates attainment of the 8-hour ozone NAAQS by 2007. In return, EPA will defer the clas sification of an area as nonattainment until 2007. The RAQC and APCD contracted with E NVIRON International Co rporation with their subcontract of Alpine Geophysics, LLC to pe rform the photochemical modeling necessary for

the Denver 8-hour ozone EAC SIP. At the ou tset of the EAC modeling, the DMA was in attainment of the 8-hour ozone NAAQS. However, the monitored ozone concentrations during

the summer of 2003 resulted in violations of th e 8-hour ozone standard. Because of the EAC,

EPA classified the DMA as “nonattainment deferre d”, with final designation to be determined

after the 2007 ozone se ason. More details on the Denver 8-hour EAC SI P are available at: http://www.raqc.org/ozone/EAC/ozone-eac.htm

Ozone attainment is based on 8-hour ozone Desi gn Values (DVs) that are defined as the threeyear average of the fourth highest 8-hour ozone c oncentration during a year at a monitor. Based on measured ozone concentrations during the 2005-2007 three-year period, the maximum 8-hour ozone DV in the DMA was 85 ppb at the Rocky Flats North (RFNO) monitoring site, which exceeds the 8-hour ozone NAAQS. Consequently, in November 2007 the DMA reverted to an

8-hour ozone nonattainment area a nd the RAQC/APCD is charged wi th developing a new 8-hour ozone SIP emissions control plan that demonstrat es the DMA will achieve attainment of the 0.08 ppm 8-hour ozone NAAQS by 2010.

1.1.2 New 8-Hour Ozone NAAQS

On March 12, 2008, EPA promulgated a new primary ozone NAAQS that has the same form as the 0.08 ppm 8-hour ozone NAAQS, but lowers the threshold from 0.08 ppm (85 ppb) to 0.075 ppm (75 ppb). Of the ~14 ozone monitors in the greater DMA, ha lf have 2005-2007 8-hour ozone DVs that are 75 ppb or higher. The cu rrent Denver 8-hour ozone SIP modeling effort addresses the 0.08 ppm 8-hour ozon e NAAQS. The designations of 8-hour ozone nonattainmentF:\Denver_O3_2008\Reports\2006_B ase_Case\Draft_Final\Sec1_MPE _Intro1.doc August 2008 

### 1-2 areas under the new 0.075 ppm 8-hour ozone NAAQS will be made in 2010 based on 2007-2009

observed ozone concentrations w ith subsequent SIPs due in 2013. Attainment of the new 8-hour ozone NAAQS will be required by 2016 (modera te) to 2030 (extreme) depending on the

nonattainment area classification.

1.2 PURPOSE

With the Denver region needing to quickly devel op an 8-hour ozone attain ment control strategy for the SIP, ENVIRON and Alpine were reen listed to prepare the photochemical modeling databases necessary to develop a control plan th at demonstrates attainment of the 8-hour ozone standard by 2010. The ENVIRON/ Alpine Modeling Team are employing the fifth generation Mesocale Model (MM5) meteorological model (Anthes and Warner, 1978; Dudhia, 1993), the Sparse Matrix Operating Kernel Emissions (SMOKE) modeling system (Coats, 1996) and the Comprehensive Air-quality Model with extensions (CAMx) photochemical grid model (ENVIRON, 2008) to model ozone in the Denver area for a June-July 2006 modeling period for the purposes of demonstrating attainment of the 8-hour ozone standard by 2010. The 8-hour ozone modeling activities being performed by th e ENVIRON/Alpine Modeli ng Team consists of the following activities:

• Development of a Denver 8-hour ozone SIP a ttainment demonstration Modeling Protocol (Morris et al., 2007; http://www.ozoneaware.org/documents /DraftFinalProtocolDenver8- HourOzoneNov282007.pdf );

• Development of a preliminary 36/12/4 km photochemical modeling database for the June-July 2006 episode, the DMA, and initia l model performance evaluation, sensitivity test modeling and identification of optimal model configuration for simulating ozone in the DMA (Morris et al., 2008);

• Final base case modeling and model perfor mance evaluation for the June-July 2006 DMA episode (this document);

• 2010 base case modeling, emission sensitivity tests and ozone source apportionment modeling (in progress); and

• 2010 control strategy modeling (in progress).

A previous report documented the results of the preliminary application and evaluation of the photochemical modeling system for the June-J uly 2006 period using the initial model configuration and includes resu lts of diagnostic tests designed to improve model performance and recommendations for a final optimal model configuration for the 8-hour Denver ozone SIP (Morris et al., 2008). This re port presents the final 2006 base case modeling and model performance evaluation for the June-July 2006 episode.

1.3 OVERVIEW OF MODELING APPROACH

The Denver 8-Hour ozone SIP modeling incl udes emissions, meteorological and ozone simulations using a nested 36/12/4 km grid with the 4-km grid focused on the state of Colorado including the DMA and vicinit y. The procedures for conducting the Denver SIP ozone modeling are outlined in a Modeling Prot ocol (Morris et al ., 2007). The Denver 8-hour ozone modeling approach was to develop an initial 36/12/4 km modeling database for the June-July 2006 episode using the MM5 meteorological, SMOKE emissions and CAMx photochemical grid models thatF:\Denver_O3_2008\Reports\2006_B ase_Case\Draft_Final\Sec1_MPE _Intro1.doc August 2008 

### 1-3 is described by Morris and co-workers (2008 ). The preliminary photochemical modeling identified an optimal model conf iguration for the final 2006 base cas e that is described in this report. The emissions were also updated for the final 2006 base case modeling. In addition to obtaining revised and corrected emissions from the APCD for Colorado, the following two

additional emission invent ory enhancements were made for th e final 2006 base case emissions inventory:

• Generation of refined on-road mobile source emissions using the CONCEPT emissions model and link-based Vehicle Miles Travelled (VMT) data from the Denver Regional Council of Government (DRCOG) Travel Demand Model (TDM); and

• Use of the WRAP Phase III oil and gas (O&G) emissions for the Denver-Julesburg

Basin.

Below we provide an overview of the mode ling approach and summarize emission updates performed for the final 2006 base case modeli ng. Details on the mete orological modeling, SMOKE emissions modeling and other aspects of the devel opment of the June-July 2006 modeling database are presented in the preliminary modeling report (M orris et al., 2008).

1.3.1 Modeling Domains

Figure 1-1a displays the MM5 (r ed) and CAMx (blue) 36/12/4 km modeling domains used in the Denver 8-hour ozone modeling study. These modeling domains are based on a Lambert Conformal Project (LCP) using th e parameters given in Table 1-1. The MM5 modeling domains are defined slightly larger than the CAMx domains in order to allow the MM5 model to eliminate any boundary artifacts that occur as the MM5 model brings the meteorological variables specified in the boundary conditions into dynamic balance with each other. Details on the Denver June-July 2006 MM5 meteorological m odeling are provided in a companion report to this one (McNally et al., 2008).

The SMOKE, ConCEPT, MEGAN and GloBEIS emissions models use the same modeling

domains as CAMx. Table 1-2 li sts the number of rows and columns and the definition of the X and Y origin (i.e., the southwest corner) for the 36/12/4 km domains used by MM5, CAMx and the SMOKE, CONCEPT and MEGAN emissions models. In Table 1-2 “Dot” refers to the grid

mesh defined at the vertices of the grid cells while “Cross” refers to the grid mesh defined by the grid cell centers. Thus, the dimension of the dot mesh is equal to the cross mesh plus one. Figure 1-1b displays the SMOKE/CAMx 12/4 km modeling domains. The CAMx model was first applied to the 36 km continental U.S. domain using boundary conditions (BCs) from a global climate air quality model (Figure 1-1a). The CAMx 2006 base case modeling results from the 36 km continental U.S. domain simulation are then processed to generate BCs for the CAMx 12/4 km domain (Figure 1-1b). The CAMx 2006 ba se case simulations for the 12/4 km domains were run using two-way interactive grid nesting (i.e., pollutants can flow back and forth between the 12 km and 4 km domains to account for recirculation).F:\Denver_O3_2008\Reports\2006_B ase_Case\Draft_Final\Sec1_MPE _Intro1.doc August 2008 

### 1-4 Table 1-1. Lambert Conformal Projection (LCP) defini tion for the Denver 36/12/4 km modeling grids.

Parameter Value

Projection Lambert-Conformal

1 st True Latitude 33 degrees N

2 nd True Latitude 45 degrees N Central Longitude -97 degrees W Central Latitude 40 degrees N



### Table 1-2. Grid definitions for MM5, Emissions and CAMx modeling domains.

-2880-2520-2160-1800-1440-1080 -720 -360 0 360 720 1080 1440 1800 2160 2520 2880 -2160 -1800 -1440 -1080

-720 -360 0 360 720 1080 1440 1800 2160

MM5 36 km CAMx 36 km MM5 12km CAMx 12km MM5 4km CAMx 4



### Figure 1-1a. Nested 36/12/4 km modeling domains for the Denver 8-hour ozone modeling study. Blue line domains are for CAMx/SMOKE domains that are nested in the MM5 red line

domains. M ODEL C OLUMNS

DOT ( CROSS ) ROWS

DOT ( CROSS ) X ORIGIN ( KM ) Y ORIGIN ( KM )

MM5 36 km grid 12 km grid 4 km grid 165 (164) 187 (186) 151 (150) 129 (128) 157 (156) 136 (135) -2952.0

-1836.0
-984.0 -2304.0

-936.0
-324.0
Emissions/CAMx 36 km grid 12 km grid 4 km grid (148) (167) (119) (112) (92) (119) -2736.0

-1704.0
-940.0 -2088.0

-624.0
-940.0F:\Denver_O3_2008\Reports\2006_B ase_Case\Draft_Final\Sec1_MPE _Intro1.doc August 2008 

### 1-5 -1680-1560-1440-1320-1200-1080 -960 -840 -720 -600 -480 -360 -240 -120 0 120 240 -600 -480 -360 -240 -120 0 120 240 360 480

CAMx 12km CAMx 4km



### Denver CAMx 12 and 4 km Domain
Figure 1-1b. Nested 12/4 km modeling domains for t he Denver CAMx air quality and SMOKE emissions modeling.



### 1.4 EMISSIONS MODELING APPROACH

The emission inputs for the Denver June-J uly 2006 8-hour ozone modeling episode were prepared in two phases. In the first phase, a Fast Track model-ready emissi ons inventory was developed in late 2007 using the SMOKE emissions model for all anthropogenic emissions and the GloBEIS model for biogenic emissions (Mo rris et al., 2008). Th e CDPHE/APCD provided

2006 emissions for Colorado counties with the rest of the region using the WRAP and other RPO 2002 emissions projected to 2005. The Fast Track emissions inventory was used for initial diagnostic testing and model performance evaluati on of the CAMx model (M orris et al., 2008). The CDPHE provided revised 2006 base case emi ssions for Colorado that contained several updates and corrections. In addi tion, emissions for on-road mob ile sources in the DMA and oil and gas sources were updated as described below.

1.4.1 SMOKE Emissions Modeling Approach

CAMx-ready emissions were generated using the Sparse Matrix Operat or Kernel Emissions (SMOKE) emissions modeling system (Coats, 1996) for all anthropogenic emissions categories except on-road mobile sources in the DMA, whic h used the Consolidated Community Emissions Processing Tool (ConCEPT) modeling system (L oomis et al., 2005). The final 2006 base case biogenic emissions were based on the Model of Emissions of Ga ses and Aerosols from Nature (MEGAN) biogenic emissions model (G uenther and Wiedinmyer, 2004).

Emissions inventory development for episodic 8-hour ozone modeling must address several source categories including: (a) st ationary point sources; (b) ar ea sources; (c) on-road mobileF:\Denver_O3_2008\Reports\2006_B ase_Case\Draft_Final\Sec1_MPE _Intro1.doc August 2008 

### 1-6 sources; (d) non-road mobile sources; (e) biogenic sources; and (f) fire sources. For this analysis, these estimates were developed for the June-July 2006 modeling period, the 36, 12 and 4 km grids (Figure 1-1) and the CB05 chemical mechanism.

CAMx requires two emission input files: (1) low-level gridded emissions that are emitted directly into the first layer of the model from so urces at the surface with little or no plume rise; and (2) elevated point sources (stacks) with pl ume rise calculated from stack parameters and meteorological conditions.

1.4.1.1 SMOKE Configuration

The CAMx-ready emission files for anthropogeni c emissions and the Fast Track emissions modeling were prepared using the SMOKE emis sions modeling system. The SMOKE emissions model performs the following tasks:

Temporal Adjustments : Adjust emission rates for seas onal, day-of-week and hour-of-day effects. The temporal allocation factors us ed are standard SMOKE adjustment factors, supplemented with state and county specifi c adjustments developed during the RPO modeling process.

Chemical Speciation : Emission estimates for total VOC are converted to the more detailed chemical speciation used by the Carbon Bond 5 (CB05) chemical mechanism in CAMx. Total unspeciated NOx emissions ar e allocated to NO and NO2 components.

The SMOKE emission model includes defa ult speciation profiles by SCC codes.

Spatial Allocation : Area and non-road mobile sources are estimated at the county level, and are allocated to the grid cells within each county ba sed on spatial surrogates (e.g., population and economic activity). On-road mobile source emissions are also allocated to grid cells, using spatial surrogates based on roadway locations and population. The latest spatial surrogates available from EPA, dated April 2004, and were used in the emissions modeling. ( http://www.epa.gov/ttn/chief/ emch/spatial/newsurrogate.html )

Quality Assurance : SMOKE includes quality assurance (QA) and reporting features to keep track of the adjustments at each processing stage and ensure that data integrity is not compromised.

The outputs from the emissions model are call ed the “model-ready” emissions, and are dayspecific, gridded, speciated and temporally (h ourly) allocated. SMOKE performs all of the processing steps for the anthropogenic emissions. The biogenic emissions were prepared using the MEGAN model using hourly MM5 meteorologi cal data and gridded biomass type and density information.

The configuration used in the SMOKE emissions modeling for the final Denver 2006 base case

simulation is shown in Table 1-3. More detail s on the SMOKE emissions modeling is provided in the preliminary evaluation and sensitiv ity modeling report (Morris et al., 2008).F:\Denver_O3_2008\Reports\2006_B ase_Case\Draft_Final\Sec1_MPE _Intro1.doc August 2008 

### 1-7 Table 1-3. Summary of SMOKE configuration parameters and data inputs.

Emissions Component Configuration Details

Model Code SMOKE Version 2.2 www.cmascenter.org

Horizontal
Grid Mesh 36/12/4 km

36 km grid 148 x 112 cells 12 km grid 167 x 92 cells 4 km grid 119 x 119

Area Source

Emissions 2006 CDPHE/APCD for Colorado 2005 projected from 2002 RPO
outside Colorado SMOKE processing

On-Road
Mobile
Sources SMOKE-MOBILE6 County HPMS VMT and SMOKEMOBILE6 In DMA replaced by CONCEPT link-based

VMT mobile source emissions

Point Sources 2006 day-specific CEM Projected 2002 RPO outside
Colorado Use 2006 day-specific hourly CEM for actual and processed CEM for Typical
2006 emissions

Off-Road

Mobile
Sources 2006 CDPHE/APCD for Colorado Projected 2002 RPO outside
Colorado

O&G Sources WRAP Phase III for D-J Basin
WRAP Phase II outside of D-J Bar-Ilan et al., 2008

Emissions
Data Sources 2006 CDPHE/APCD for Colorado

2002 Plan02b WRAP States Projected to 2005 2002 Base G CENRAP States Projected to 2005 2002 Base M MRPO States Projected to 2005 2002 Base G VISTAS States Projected to 2005

2006 HPMS for outside Colorado Process with SMOKE-MOBILE6 Acid Rain Database for CEM data Large stationary source NOx and SO2

O&G WRAP Phase III for D-J

Basin Biogenic
Sources MEGAN Use day-specific hourly MM5 meteorology

Wildfires 2006 From NCAR Temporal Adjustments Seasonal, day, hour Based on latest collected information updated for RPO modeling

Chemical Speciation Revised CB05 Chemical Speciation EPA updated in 2007

Gridding Spatial Surrogates based on
landuse EPA updated in 2004

Quality

Assurance QA Tools in SMOKE and CONCEPT; PAVE plots; Summary reports



### 1.4.2 Updated WRAP Phase III O&G Emissions for the D-J Basin

The Independent Petroleum Association of Mountain States (IPAMS) is sponsoring the development of a Phase III regional oil and gas emission inventory for the inter-Mountain West jointly with the Western Regional Air Partners hip (WRAP), to build on the WRAP Phase I and Phase II inventory projects (WRAP Phase III O&G Pr oject). This effort is focused on creating a comprehensive criteria pollutant emissions inventor y for all activities associated with oil and gasF:\Denver_O3_2008\Reports\2006_B ase_Case\Draft_Final\Sec1_MPE _Intro1.doc August 2008 

### 1-8 field operations in the basins throughout the study region fo r year 2006 as well as future projection years; that includes all point and area sources relate d to the oil and gas industry.

The initial region of interest for the WRAP Phase III O&G emission i nventory is the DenverJulesburg (D-J) Basin, which includes the De nver and Northern Front Range 8-hour ozone nonattainment areas. The 2006 baseline inventory consists of two primary categories: sources subject to Air Pollution Emission Notice (APEN) reporting requirements, and sources exempt from APEN reporting. The WRAP Phase III project has completed the O&G emissions development for the 2006 base and 2010 future year (Bar Ilan et al., 2008a ,b) and the reports are

available on the WRAP website at:

• http://www.wrapair.org/forums/ ssjf/documents/eictts/OilGas/2008- 04_'06_Baseline_Emissions_DJ_Basin_Technical_Memo_(04-30).pdf

• http://www.wrapair.org/forums/ ssjf/documents/eictts/OilGas/2008- 04_'10_Projection_Emissions_DJ_Basin_Technical_Memo(04-30).pdf

In general, the inventory was developed usi ng a combination of well count and production activity from a commercially available databa se of oil and gas data maintained by IHS Corporation (“the IHS database”), the State of Colorado’s database of permitted sources including APENs sources and Regulation 7 reports, and detailed survey re sponses of oil and gas activity from several major participating companies that operate in the D-J Basin. Some additional data sources were also used, includin g American Petroleum In stitute (API) technical literature, the US Environmental Protection Agen cy’s (EPA) AP-42 emissions factor technical guidance, the US EPA’s NONROAD emissions model, and the US EPA’s Natural Gas Star program technical guidance.

1.4.2.1 Temporal and Geographic Scope

The WRAP Phase III D-J O&G emissions inventor y considers a base year of 2006 for purposes of estimating emissions, consistent with the June-July 2006 modeling episode for the Denver 8- hour ozone SIP modeling. All da ta requested from participating companies were for these companies’ activities in the ca lendar year 2006. Similarly, all we ll count and production data for

the basin obtained from the IHS database were for the calendar year 2006. Emissions from all source categories are assumed to be uniformly di stributed throughout the y ear except for heaters and pneumatic pumps, which are assigned seasonal ity fractions as they are typically used primarily in winter.

The geographic scope of this inventory is the D-J Basin, whose boundaries as defined by the US Geological Survey (USGS) were used. The USGS boundaries for the D-J Basin were intersected

with the State of Colorado boundaries so that on ly the portion of the D-J Basin within Colorado was considered for this inventory. The followi ng counties were wholly contained within the

boundaries of the D-J Basi n in this inventory:F:\Denver_O3_2008\Reports\2006_B ase_Case\Draft_Final\Sec1_MPE _Intro1.doc August 2008 

### 1-9 • Adams

• Arapahoe

• Boulder

• Broomfield

• Crowley

• Denver

• Douglas

• Elbert • El Paso

• Fremont

• Jefferson

• Kit Carson

• Larimer

• Lincoln

• Logan

• Morgan • Phillips

• Pueblo

• Sedgwick

• Teller

• Washington

• Weld

• Yuma

Figure 1-2 shows the boundaries of the D-J Basin, with the 2006 well locations extracted from

the IHS database overlaid.

Figure 1-2. D-J Basin boundaries overlaid and 2006 oil and gas well locations



### .F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-10 1.4.2.2 Well Count and Production Data

Oil and gas related activity data across the entire D-J Basin were obtained from the IHS Enerdeq database queried via online interf ace. The IHS database uses data from the Colorado Oil and Gas Conservation Commission (COGCC) as a source of information for Colorado oil and gas activity. Two types of data were queried from the Enerdeq database: production data and well

data. Production data includes information releva nt to producing wells in the basin while well data includes information relevant to drilling ac tivity (“spuds”) and completions in the basin.

1.4.2.3 Sources Subject to APEN and Condensate Tanks Subject to Regulation 7

On October 31, 2007 a request was made to the APCD for the 2006 Colorado APEN database for all oil and gas related emission sources c overed by the following SCC and SIC codes:

• All of the SCCs 202002*, 310*, 404003* (where * i ndicates all sub-SCCs for the SCC)

• And only those with the following SICs: 13*, 492*, 4612.

APEN data for the D-J basin were extracted and sorted by operator. Company specific APEN source data were forwarded to pa rticipating operators for a comp leteness review that included the following three issues:

1) Source Categories that were mi ssing from the APEN database, 2) Specific sources missing from the database, and 3) Sources within the database known to be no longer operating.

Following the completeness review and the additi on or deletion of sources as appropriate,

emission rates were reviewed. Emission rates we re updated to reflect 20 06 actual emissions in cases where supporting data were available. Actual emission updates provided by operators followed the APCD calculation methodologies from existing permits or required Operation and

Maintenance Plans. The APCD methodologies are used to update Annual Emission Calculations (Minor Sources) and 12-Month Rolling Emission To tals (Synthetic Minor a nd Major Sources).

A separate request was made to APCD for a copy of the 2006 Regulation 7 atmospheric storage tank reports for year 2006. With in the Ozone Control Area, data from the Regulation 7 reports was utilized in place of the APEN data to re present stock tank emissions as the Regulation 7 reports best reflected actual emissions. The Regulation 7 reports for c ondensate tanks were in the form of monthly reports of condensate th roughput for each tank, and emissions for each tank, for all companies operating condensate tanks subjec t to Regulation 7 in th e ozone non-attainment area. A macro was written in EXCEL to pro cess the reports in such a way that monthly condensate throughput (bbl) and emissions (lb- VOC) could be extracted and summed.

Confirmation was obtained that CDPHE’s a nnual Regulation 7 condensate tank emissions summary for 2006 was in reasonable agreement with the extracted emissions from the monthly Regulation 7 reports.

GIS analysis was used to intersect the boundary of the ozone non-attainment area with the latitude/longitude coordinates of all APENs sources. Those sour ces falling within the ozone

non-attainment area were filtered to remove a ny sources that were condensate tanks, based on SCC and SCC description. For purposes of summing all permitted oil and gas sources’F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-11 emissions in the D-J Basin, emissions from th e remaining APENs sources (excluding condensate tanks in the ozone non-attainment area) were added to the summary emissions from all Regulation 7 condensate tank reports.

1.4.2.4 APEN Exempt Sources

Survey forms consisting of 11 Excel spreadsheets were forwarded to participating operators in the D-J basin. Each spreadsheet contained a reque st for specific data related to one of the following APEN exempt source categories:

• Well blowdowns

• Well completions

• Drilling rigs

• Exempt engines

• Fugitive emissions

• Heaters

• Gas composition analysis for the basin

• Pneumatic devices

• Pneumatic pumps

• Water tanks

• Workover rigs

The companies participating in the survey pro cess for the D-J Basin represented 50% of well ownership in the basin, 63% of gas production in the basin, and 58% of oil production in the basin. This represented a sufficiently large percenta ge of oil and gas activity in the basin that it was felt that the responses obtained from the part icipating companies would be representative of all oil and gas operations in the basin.

In addition to the source categories listed above , emissions from three additional APEN exempt source categories were estimated based on additi onal information requests from the participating companies:

• APEN exempt atmospheric storage tanks

• Truck loading activities

• Flaring from condensate tanks

1.4.2.5 WRAP Phase III D-J Basin O&G Summary Results

Results from the combined permitted sources (APE Ns sources excluding condensate tanks in the ozone non-attainment area, and condensate tanks in the ozone non-attainment area from the Regulation 7 reports), and the combined unperm itted sources are presented below on a county

level and as summaries for the entire D-J Basin as a series of pie charts and bar graphs.

Figure 1-3 shows that NOx emissions are primarily concentrated in Weld and Yuma counties, which is not surprising given that it is the areas of large concentrations of well locations. Figure 1-4 shows that VOC emissions are primarily c oncentrated in Weld county only. ProductionF:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-12 activity in Yuma County is mostly dry gas, a nd therefore a smaller pr oportion of total VOC emissions occur in Yuma County.

Figure 1-4 shows that compressor engines and drill ing rigs combined account for almost 80% of NOx emissions. Similarly, Figure 1-5 shows that permitted and unpermitted condensate tanks and pneumatic devices account for approxima tely 81% of VOC emissions. Table 1-4

summarizes the WRAP Phase III emissions for the D-J Basin and 2006 base case by county. A majority of the VOC (78%) and NOx (59%) D-J Basin O&G emissions come from Weld County.

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000

A dam s

A

r ap

ahoe

Boulder Broom f ld Crowley Denver Elbert

F

rem

ont

J efferson Kit Cars Lar

i m

er Lincoln Logan

M

organ

P h illi

ps

P uebl o Sedgwick Washngt n Weld Yum a

CountyNOx Emissions (tons/year) Other Categories

Glycol Dehydrator

Compressor Engines

Workover rigs

Venting - recompletions
Pneumatic devices

Permitted Fugitives

Exempt engines

Drill rigs



### Figure 1-3. 2006 NOx emissions by source category and by county in the D-J Basin.F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-13 0 20,000 40,000 60,000 80,000 100,000 120,000 140,000AdamsArapahoeBoulderBroomfldCrowleyDenverElbertFremontJeffersonKit CarsLarimerLincolnLoganMorganPhillipsPuebloSedgwickWashngtnWeldYuma

CountyVOC Emissions (tons/year) Other Categories

Glycol Dehydrator

Compressor Engines

Venting - recompletions

Venting - initial completions

Venting - blowdowns

Truck loading of condensate liquid

Small condensate tanks

Pneumatic pumps

Pneumatic devices

Large condensate tanks

Permitted Fugitives

Unpermitted Fugitives

Drill rigs



### Figure 1-4. 2006 VOC emissions by source category and by county in the D-J Basin.

Drill rigs

25%

Exempt engines

14% Other Categories

1%

Workover rigs

3% Heaters

3% Compressor Engines

55%



### Figure 1-5. D-J Basin NOx emissions proportional contributions by source category



### .F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-14 Large condensate tanks

50% Other Categories

1%

Pneumatic devices

14% Permitted Fugitives

1% Venting - recompletions

1%

Truck loading of condensate liquid

1% Venting - initial

completions

1%

Small condensate tanks

16%

Pneumatic pumps

1% Venting - blowdowns

2% Unpermitted Fugitives

9% Glycol Dehydrator

1% Compressor Engines

3%



### Figure 1-6. D-J Basin VOC emissions proportional contributions by source category.

Table 1-4. 2006 emissions of all criteria pollutants by county for O&G emissions in the D-J

Basin.

County NOx [tons/yr] VOC [tons/yr] CO [tons/yr] SOx [tons/yr] PM [tons/yr] Adams 2,286 3,005 939 13 19 Arapahoe 742 408 253 0 4

Boulder 129 803 76 1 4

Broomfield 14 193 10 0 0 Crowley 63 1 85 0 1

Denver 32 103 19 0 2 Douglas 0 0 0 0 0

Elbert 43 363 27 0 1

El Paso 0 0 0 0 0

Fremont 16 329 9 0 1

Jefferson 6 0 10 0 0
Kit Carson 10 139 6 0 1

Larimer 37 651 23 0 1

Lincoln 14 462 11 0 0 Logan 491 1,382 183 2 9 Morgan 672 883 672 132 4 Phillips 40 47 26 0 1

Pueblo 0 0 0 0 0 Sedgwick 1 11 0 0 0

Teller 0 0 0 0 0 Washington 284 4,509 207 1 9 Weld 12,310 64,111 8,393 51 421 Yuma 3,592 4,359 1,993 24 158 Totals 20,783 81,758 12,941 226 636F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-15 1.4.3 ConCEPT On-Road Mobile Source Emissions for the DMA

CONCEPT is an emissions model that performs th e three key features of emissions processing: temporal allocation of the emissions (to hourly), spatial allocation of the hourly emissions to the grid cells in the modeling doma in, and emissions speciation to develop emissions for species used by the air quality model. CONCEPT MV runs MOBILE6 to generate on-road mobile emissions in a very detailed manner. The basi c steps in the calculati on of on-road emissions using CONCEPT MV are as follows (additional details in Table 1-5):

o Activity Data Preparation . CONCEPT estimates and grids link-level emissions using the output from Transportation Demand Models (TDMs). The TDM Transformation Tool, or T3, to processes the traffic demand model vehicle types, road networks, and vehicle activity to the file formats required by CONCEPT.

o Temporal Allocation . Transportation demand model (T DM) data are typically provided for multi-hour periods. CONCEPT uses the total VMT hourly, daily, and monthly temporal profiles to split the multi-hour volumes to hourly volumes per link.

o Speed Adjustment . CONCEPT calculates hourly volum e/capacity ratios and applies adjustments to the free-flow speed s to account for congestion.

o Spatial Allocation . The vehicle activity data for e ach link for each hour are spatially allocated to grid cells using an overlay of the link network on the model grid.

o VMT Mix Profiles . VMT data are split into eight vehicle classes using the vehicle mix temporal profiles that vary by hour of da y, day of week, and month of year.

o Execute MOBILE6 . MOBILE6 is executed by CONCEPT-MV for each link in each grid cell using the link-specific speed and grid-s pecific temperature and humidity from the MM5 modeling data files, and county- specific MOBILE6 model inputs.

o Calculate link-level emissions . Emissions for each vehicle class, emission type, and pollutant for each link in each grid cell are es timated as the product of the emission factor

and the VMT for each vehicle class.

o Speciate the Emissions . CONCEPT MV applies the appr opriate speciatio n profiles by pollutant and emission mode to generate the speciated emissions and create model-ready files for CMAQ or AERMOD.F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-16 Table 1-5 . Summary of CONCEPT parameters and data inputs.

Emissions Component Configuration Details Activity data preparation T3 used to format TDM
data TransCAD output from DRCOG

Temporal allocation Total volume and vehicle mix profiles generated from
automated traffic counter
data in the DMA The traffic counter data was provided by the Department of Transportation. A discussion of the traffic counter data analysis is provided in Appendix A. Speed adjustment BPR volume-delay applied by road type Curve coefficients pr ovided by DRCOG

Spatial allocation Links gridded to the 4km nest by CONCEPT VMT mix profiles Vehicle mix profiles generated from automated
traffic counter data in the

DMA The traffic counter data was provided by the Department of Transportation

Execute MOBILE6 MOBILE6 inputs provided by CDPHE CONCEPT uses a customized version of M6 (developed by Air Improvement Resource [AIR] under contract to LADCO) that summarizes the database output across model years within vehicle classes, and into the eight MOBILE5 vehi cle classes employed
in CONCEPT Speciate emissions The CB05 speciation profiles were developed for

EPA QA Output reports from both T3
and CONCEPT. Comparison with county totals generated by Alpine Geophysic’s application of
the SMOKE model T3 summaries of VMT by county and time period provided to CONCEPT. CONCEPT reports of emissions (in tons) by county, emissions by vehicl e type and emissions mode, summaries of M6 runs, total emissions in tons, hourly VMT, and summaries of adjusted and unadjusted speeds.



### The transportation demand model (TDM) data us ed in the CONCEPT mo deling were provided by the Denver Regional Council of Governments (DRCOG) from their Integrated Regional Model. The activity data included:

• Link Characteristics : Start and end node coordinate s, link length, free-flow speeds, roadway type, hourly capacity, and county.

• Link Volumes : Period-level directional total wee kday average volumes for the following ten time periods: 630 – 700, 700 – 800, 800 – 900, 900 – 1130, 1130 – 1500, 1500 – 1700, 1700 – 1800, 1800 – 1900, 1900 – 1900 – 2300, 2300 – 630. The period-level volume was pre-processed to w hole hours, and then CONCEP T further disaggregated the volumes to hourly values using the temporal profile inputs.

• Speed Adjustment : Bureau of Public Roads (BPR) speed adjustment curve coefficients

A plot of the 2005 transportation netw ork is presented in Figure 1-7.F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-17 Figure 1-7. DRCOG link-based transportation network used in the CONCEPT on-road mobile source emissions modeling.F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-18 Area Type

The area types in the TDM output were represente d by numeric codes that were translated as

follows:

Code Description Urban/Rural

1 CBD Urban 2 Fringe Urban

3 Urban Urban

4 Sub-Urban Urban

5 Rural Rural



### Roadway Type

The TDM functional classes were provided as nu meric codes that were translated to HPMS roadway types as follows:

Code Urban/Rural Functional Class HPMS Type (Code) 1 Rural freeway Principal Arterial - Interstate (01) 2 Rural major regional arterial Principal Arterial - Other (02) 3 Rural principal arterial Principal Arterial - Other (02) 4 Rural minor arterial Minor Arterial (06) 5 Rural collector Major Collector (07)

6 Rural ramp Ramp (added to CONCEPT for modeling purposes) (03) 8 Rural zone connector Local System (09) 1 Urban freeway Principal Arterial - Interstate (11)

2 Urban major regional arterial Principal Arterial - Other Freeways or Expressways (12) 3 Urban principal arterial Principal Arterial - Other (14) 4 Urban minor arterial Minor Arterial (16) 5 Urban collector Collector (17)

6 Urban ramp Ramp (added to CONCEPT for modeling purposes) (13) 8 Urban zone connector Local System (19)



### The VMT was calculated as the volume times the link length. Note that the VMT from the TDM

centroid connectors was included as local road VMT.

Growth

DRCOG provided TDM output for 2005, 2015, and 2020 . The 2005 transportation data were grown to 2006, and the 2015 data were back casted to 2010 using the county-level growth and back casting factors interpolated betw een the 2005 and 2015 county-level VMT.

The county total VMT from the TDM and the 2006 a nd 2010 interpolated tota ls are presented in

Table 1-6.F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-19 Table 1-6. Annual county-level total av erage weekday VMT from the TDM.

County 2005 2006 Interpolated 2010 Interpolated 2015 2020
Adams 10,922,773 11,289,709 12, 757,453 14,592,132 16,440,119 Arapahoe 10,931,247 11,253,596 12, 542,993 14,154,738 15,673,382
Boulder 5,737,221 5,824,590 6 ,174,064 6,610,906 7,014,825
Broomfield 2,006,314 2,040,202 2 ,175,753 2,345,192 2,620,702
Clear Creek 36,082 38,101 46,175 56,267 70,371
Denver 14,430,681 14,731,101 15,932,782 17,434,883 18,292,519 Douglas 7,877,685 8,144,715 9 ,212,837 10,547,989 11,777,265 Gilpin 14,933 15,170 16,119 17,305 18,872
Jefferson 13,148,925 13,385,173 14,330,163 15,511,400 16,614,625
Weld 2,746,625 2,879,718 3, 412,088 4,077,550 4,651,258
Total 67,852,486 69,602,074 76, 600,424 85,348,362 93,173,938



### Speed Adjustment

After CONCEPT disaggregated the total volumes into hourly values, the free-flow speeds were adjusted to congested speeds as appropriate us ing the most common volume-delay function (the Bureau of Public Roads curve, or BPR curve). The general form of this function is defined as:



# ( ) ⎥ ⎦ ⎤ ⎢ ⎣ ⎡
+ = B ff

a


### C V A S S

* 1

where:



### S

a = actual link speed (mph)



### S

ff

= reported link free flow speed (mph)



### V

= total link volume (vehicles OR vehicles per hour)



### C

= total link capacity (vehicles OR vehicles per hour)



### A, B = curve calibration coefficients



### The A and B coefficients employed were the revised coefficients in DRCOG’s Highway Skimming and Assignment Documentation, Decemb er 2004. The roadway-sp ecific coefficients are presented in Table 1-7.F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-20 Table 1-7. BPR speed adjustment coefficients used in estimating congested speeds.

A coefficients

Area Type Freeway Major
Arterial Principal Minor
Arterial Collector

CBD 0.70 0.10 0.20 0.20 0.20 Fringe 0.70 0.10 0.30 0.30 0.30

Urban 0.40 0.25 0.40 0.40 0.40

Suburban 0.40 0.25 0.40 0.40 0.40

Rural 0.40 0.40 0.40 0.40 0.40

B Coefficients

CBD 5.50 7.50 5.00 5.00 5.00 Fringe 5.50 7.50 5.00 5.00 5.00

Urban 7.50 7.50 5.50 5.50 5.50

Suburban 7.50 7.50 5.50 5.50 5.50

Rural 5.00 5.00 5.00 5.00 5.00



### The speeds of local roads were not adjusted.

Weekday/weekend Temporal Adjustment

CONCEPT disaggregates period-level VMT into hourly valu es by assigning the relative proportion of VMT for a given hour within a pe riod based on the hourly temporal profiles.

Because the TDM data are reflec tive of weekday volumes, we generated a second set of inputs to CONCEPT for the weekend day simulations wh ere the period-level VMT were summed to create a daily total. This daily total was then fed to CONCEPT, which then disaggregated the VMT according to a true weekend temporal distribution.

Additional Temporal Adjustments

We received from the Colorado Department of Transportation 2005 and 2006 total volume and

vehicle classification data in the DMA from automated traffic counters. The volume data

consisted of the total number of vehicles c ounted on a roadway by day and hour. The vehicle mix profiles were generated usi ng vehicle classification data pr ovided by CDOT that counted the

number of vehicles of each di fferent class by day a nd hour. Data from both years was merged together in the temporal analysis; in ot her words, no distinction was made by year.

All the observation sites in the total volume and vehicle classification data were assigned to a Federal Highway Administration (FHWA) roadway function class. The cross-reference between the CDOT roadway classifications and FHWA classifications are presented in Table 1-8.F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-21 Table 1-8. FHWA Roadway functional classification. CDOT Road Type FHWA Classification and Code Collector Urban Collector (17) Freeway Urban Interstate (11) Interstate Urban Interstate (11) Major Regional Urban Principal Arterial - Other Freeways or Expressways (12) Minor Arterial Urban Minor Arterial (16) Other Principal Arterial Urban Principal Arte rial - Other Freeways or Expressways (12) Principal Urban Major Arterial (14) Principal Arterial Urban Major Arterial (14)



### The vehicle classes in the classi fication data are somewhat differe nt than the vehicle classes in MOBILE5 or MOBILE6. They are presented in Table 1-9.

Table 1-9. Vehicle classifications.

FHWA
Class VTRIS Vehicle Type

1 Motorcycle 2 Passenger cars 3 Other 2-axle, 4-tire single unit vehicles

4 Buses 5 2-axle, 6-tire single-unit vehicles 6 3-axle, 6-tire single-unit vehicles 7 4+ axle single-unit vehicles

8 4 or less axle combination vehicles

9 5-axle combination vehicles

10 6+ axle combination vehicles

11 5-axle multi-trailer vehicles

12 6-axle multi-trailer vehicles

13 7+ axle multi-trailer vehicles
14 Unclassified

15 Unclassifiable



### The estimated fraction of each FHWA vehicle class assigned to the MOBILE5 vehicle classes is

shown in Table 1-10.

Table 1-10. Fractional Allocation of FHWA Vehicle Classes to MOBILE5 Vehicle Classes.

FHWA
Class LDGV LDGT1 LDGT2 HDGV LDDV LDDT HDDV MC

1 0 0 0 0 0 0 0 1

2 0.52225 0.35340 0.11183 0.00748 0.00085 0.00180 0.00238 0

3 0.51365 0.34758 0.11956 0.00689 0.00084 0.00190 0.00957 0

4 0 0 0 0.16928 0 0 0.83072 0

5 0 0.24070 0.19405 0.12262 0 0.00287 0.43976 0

6 0 0.24070 0.19405 0.12262 0 0.00287 0.43976 0

7 0 0.24070 0.19405 0.12262 0 0.00287 0.43976 0

8 0 0.00031 0.00701 0.02044 0 0.00010 0.97214 0

9 0 0.00031 0.00701 0.02044 0 0.00010 0.97214 0

10 0 0.00031 0.00701 0.02044 0 0.00010 0.97214 0

11 0 0.00031 0.00701 0.02044 0 0.00010 0.97214 0

12 0 0.00031 0.00701 0.02044 0 0.00010 0.97214 0

13 0 0.00031 0.00701 0.02044 0 0.00010 0.97214 0F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-22 The CDOT data was read into a Microsoft SQL Server database. The total volume and vehicle classification data was processed in the following steps:

1) All counts across lanes in the same roadway di rection were totaled. Different directions at site were treated separately. 2) All counts (either total volume or count for each vehicle class) were averaged for each site-direction pair by hour, day of week (i.e., Sunday th rough Saturday), month, and roadway classification. This means that at most five values were averaged together, corresponding to the total number of days in a week during one month. In other words, all Monday counts during January for hour 10 were averaged together at each sitedirection pair. This averaging by site first was done so that sites that may not have had as long a period of observation would be weighted equally in the aver age across the sites. 3) The counts were averaged acro ss the sites. These averages were calculated by roadway function class, vehicle class, mont h, day of week, and hour of the day. 4) Any holes in the data (where either data wa s missing or the data was not representative)

were filled in. 5) The FHWA vehicle classes were mapped into MOBILE5 vehicle classes.

To calculate the temporal profiles, the total volume by roadway class was tallied for the year, month, and day of week. The monthly profile fr actions were calculated by dividing the monthly totals by the yearly total. The day of week profiles were calcul ated by dividing the day of week totals by the monthly total for each month. Finally the hourly totals were calculated by dividing the hourly counts by the day of week totals (su mmed over all 24 hours) for each day of week and month. Each row in the temporal profiles sum to 1.

The vehicle mix profiles were calcu lated as the fractions contributed by each vehicle class to the total hourly volume. So for each roadway func tion class, month, day of week, and hour, the hourly vehicle mix profiles were calculated by dividing each vehicle cl ass count by the total

volume for that hour.

Before proceeding with the analysis, the following data was dropped to ensure the integrity of the profiles:

• Dropped 65 duplicate 2005 vehicle classifica tion records corresponding to 10/29/2005 at sites 3, 103, 108, 124, 215, 245, 247, 256, 504, 507, 512, 609, 103608, 103694, 103712,

and 11/13/2005 at site 107.

• Removed duplicated “05” records from the total volume data, where identical volume counts were recorded with the year “2005.”

• Replaced corrupted 2006 classification ta ble stations 10, 12 & 103387 with corrected data, and dropped 144 records of other co rrupted records in this dataset.

• Dropped the vehicle classification sites 7, 215 & 247 corresponding to FHWA facility class 16 (Minor Arterial) because according to CDOT, they were not representative of the

Denver Area.

• Dropped all vehicle classification records for which the total hourly volume was less than

3.

• Dropped all records for which more than 25% of the hours in a day had zero volume.

• Dropped all records for which there were not 24 hours of observations in a day.

• Dropped sites for which there was not a complete week in a given month.F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-23 • For the total volume monthly profiles, droppe d all sites for which there were not 12 months worth of data after incomplete weeks were dropped.

There was enough data to create profile s for the following facility classes:

01 – Rural Interstates 02 – Rural Principal Arterials – Other

06 – Rural Minor Arterials

11 – Urban Interstates 12 – Urban Principal Arterials – Other Freeways or Expressways 14 – Urban Principal Arterials – Other

We did not have enough data from the remaining classes: 07 (Rural Major Collector), 08 (Rural Minor Co llector), 09 (Rural Local), 16 (Urban Minor Arterial), 17 (Urban Collector), or 19 (Urban Local). For the to tal volume profiles, we used the profiles generated for class 06 and applied them to classes 07, 08, and 09. We applied the total volume profiles from class 14 to classes 16, 17, and 19.

Figures 1-8 through 1-10 display th e monthly, July day of week, a nd July urban interstate hourly total volume temporal profiles. Figures 1-11 an d 1-12 display the vehicle mix hourly profiles for rural and urban interstates for a week in July.

Denver Monthly Traffic Timeseries by Facility Class

0 0.02 0.04 0.06 0.08 0.1 0.12

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

MonthFraction of Total Traffic FC1

FC2

FC6

FC11

FC12

FC14



### Figure 1-8. Monthly temporal profiles for facility classes 1 through 14.F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-24 Denver Day of Week Profiles for Urban Interstates (NFC=11)

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

Sun Mon Tue Wed Thu Fri Sat

DayFraction of Total Traffic

Jun

Jul



### Figure 1-9. Day of week temporal profiles for June and July.

Denver Hourly Profiles for Urban Interstates (FC=11)

0 0.02 0.04 0.06 0.08

1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21

HourFraction of Total Traffic

Jun

Jul



### Figure 1-10. Hourly temporal profiles for urban interstates for a week in June and July.F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-25 Denver Rural Interstates (NFC=1), July Hourly Class Fractions Sunday through Saturday

0 0.1 0.2 0.3 0.4 0.5 0.6

1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21

HDDV HDGV LDDT LDDV LDGT1 LDGT2 LDGV MC 

### Figure 1-11 . Vehicle mix hourly profile for rural interstates in July.

Denver Urban Interstates (NFC=11), July Hourly Class Fractions Sunday through Saturday

0 0.1 0.2 0.3 0.4 0.5 0.6

1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21 1 5 9 13 17 21

HDDV HDGV LDDT LDDV LDGT1 LDGT2 LDGV MC 

### Figure 1-12. Vehicle mix hourly profile for urban interstates in July.F:\Denver_O3_2008\Reports\2006_Base_Case\Dr aft_Final\Sec1_MPE_Intro1.doc August 2008 

### 1-26 Combining ConCEPT DMA and SMOKE Colorado On-Road Mobile Emissions

The SMOKE-MOBILE6 and CONCEPT on-road mobile source emissions modeling both produced on-road mobile source emissions for the area covered by the DRCOG link-based VMT network. To avoid double counting on-road mobile source emissions in the DMA, a mask was developed that identified all 4 km grid cells that were covered by the DRCOG link-based

network. The SMOKE-MOBILE6 on-road mobile source emissions in the area covered by the DMA mask were then eliminated so that they were replaced by the CONCEPT derived on-road

mobile source emissions when the SMOKE-M OBILE6 and CONCEPT files were merged together.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-1 2.0 OZONE OPERATIONAL MOD EL PERFORMACE EVALUATION

2.1 INTRODUCTION

This Chapter describes the operational model performance evaluation fo r ozone and the final CAMx 2006 base case simulation (Run 17) of the June-July 2006 modeling period using the final model configuration. That is, the ozone operational model initial evaluation focuses on how well the model reproduces the observed surf ace ozone concentrations during the June-July 2006 modeling period. In Chapter 3 we present a diagnostic mode l performance evaluation that focuses on the model performance for ozone pr ecursors (VOC, NOx and CO), ozone aloft and particulate matter (PM) species.

2.1.1 Purpose of the Model Performance Evaluation

The purpose of the model performance evaluation is to establish a relia ble CAMx 8-hour ozone modeling database for the DMA that can be us ed for projecting future year 8-hour ozone concentrations. In general terms, this process consists of the following cycle:

• Exercise the modeling system for a series of base case simulations attempting to replicate the time and space behavior of the observed 1-hour and 8-hour ozone

concentration fields as well as concentr ations of precursor and product species;

• Identify sources of error and/or co mpensating biases, th rough evaluation of preprocessor models (MM5, SMOKE, CONC EPT, GloBEIS, MEGAN), air quality model inputs, concentrations aloft, mass budgets and conservation, process analysis,

etc;

• Through a documented process of diagnostic and sensitivity investigation, pinpoint and correct the performance problems via model refinement, additional data collection and/or analysis, or theoretical considerations;

• Re-run the model for the refined base case and re-evaluate performance until adequate, justifiable performance is achieved or the modeling period is declared unsuited for further use based on documented performance problems.

In practice this process is limited by time and resource constraints. The preliminary model performance evaluation and diagnostic sensitivity tests performed most of the elements listed above (Morris et al., 2008b), wher eas this document focuses on the last item; the documentation of the model performance of the final 2006 base case simulation and justif ication for its use in the 8-hour ozone attainment demonstration modeling.

2.1.2 Approach for the Operational Ozone Model Evaluation

The CAMx performance evaluations follows the procedures recommended in the EPA photochemical modeling guidance documents (EPA, 1991; 1999; 2005a; 2007). The evaluation was carried out in two sequentia l phases, beginning with the si mplest comparisons of modeled and observed ground-level ozone con centrations presented in this Chapter follows by potentiallyF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-2 more illuminating analyses presented in Chapter 3 (e.g., examination of available precursor and product species, comparisons of pollutant ratios and groupings, comparison against PM species, deposition and visibility). The CAMx evaluati on will use most of the following six means for assessing photochemical model pe rformance as specified in EPA’s guidance are as follows:

• Use of computer generated graphics;

• Use of ozone metrics in statistical comparisons;

• Comparison of predicted and observed precurs or emissions or species concentrations;

• Comparison of observed and predicte d ratios of indicator species;

• Comparison of predicted source category cont ribution factors with estimates obtained using observational models as available; and

• Use of retrospective analyses in which air quality differences predicted by the model are compared with observed trends.

The Denver model performance evaluation focuses ma inly on the first three of these elements for evaluating model performance, with some presentation of the fourth element that compares some predicted and observed indicator ratios presented in Chapter 3. The Denver ozone modeling did not perform any ozone source apportionment modeling for the 2006 base case, although such modeling was performed for the 2010 base case emissi ons scenario that is reported with the 2010 modeling. In addition, we did not perform any retrospective modeling to compare the modeling system’s response to past changes in emissions . Although in hindsight, the Denver 8-hour ozone EAC SIP modeling of the June-July 2002 epis ode using essentially the same MM5/CAMx modeling system did perform some prospective modeling where the modeled changes in ozone between 2002 and 2007 compared favorable with the observed changes. The maximum 2007 projected 8-hour ozone Design Value predic ted by the CAMx model using the 2002 EAC modeling database was 85 ppb at th e Rocky Flats North monitor, wh ich agreed exactly with the

observed 2005-2007 8-hour ozone Design Value at that site.

2.1.2.1 Available Aerometric Data for the Evaluations

The model performance evaluation is limited by the availab ility of monitoring da ta in the region. Table 2-1 and Figure 2-1 display the ozone monito ring network in the DMA and vicinity. Also shown in Table 2-1 are the years of operation of the Denver ozone monitoring sites. Note that the Chatfield (CHAT) site was moved in 2004. The 2010 8-hour ozone Design Value projections will be based on current year Design Values from the 2005-2007 period, so only sites with ozone observations from those years will have monitor-specific Design Value projections. Although a two-year Design Value (2006-2007) was used for the Fort Collins West monitor that

started in 2006.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-3 Table 2-1. Ozone monitors operating within and near the DMA during 2002-2007.

ID Number Site Name Site ID 2002 2003 2004 2005 2006 2007 Lat Long 080013001 Welby WELB x x x x x x 39.838 -104.950 080050002 Highland HIGH x x x x x x 39.568 -104.957

080130011 S. Boulder Creek SBC x x x x x x 39.957 -105.238

080310002 CAMP CAMP x x x 39.751 -104.988 080310014 Carriage CARR x x x x x x 39.752 -105.031

080350002 Chatfield #1 CHAT x x x 39.538 -105.065

080350004 Chatfield #2 CHAT x x x x 39.534 -105.070 080410013 USAF Academy ACAD x x x x x x 38.958 -104.817 080410016 Manitou Springs MANI x x x x 38.853 -104.901

080590002 Arvada ARVA x x x x x x 39.800 -105.100

080590005 Welch WELC x x x x x x 39.639 -105.139

080590006 RFN RFNO x x x x x x 39.913 -105.189

080590011 NREL NREL x x x x x x 39.744 -105.178

080590012 Lookout Mountain LOOK x 39.727 -105.247

080690007 RMNP RMNP x x x x x x 40.277 -105.545

080690011 FtC West FTCW x x 40.593 -105.141

080691004 Ft. Collins FTCO x x x x x x 40.577 -105.079 081230007 Greeley GREE x 40.416 -104.692

081230009 Weld Co. Tower WCTO x x x x x x 40.386 -104.737

-800 -760 -720 -680 -640 -600 -120 -80 -40

0 40 80 120

SBC

ACAD ARVA
NREL RMNP FTCW

GREE

NIWOT

CHAT CHAT

MANI FTCO

WCTO

CARR WELB

HIGH CAMP RFNO

WELC LOOK



### Figure 2-1. Location of ozone monitoring sites within and near the Denver Metropolitan Area (DMA) (triangle symbols point to monitor identifier).F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-4 During 2006, two of the routine monitoring sites (CAMP and WELB) also collected NO2

measurements in the DMA and 13 mon itors collected CO as well.

We are aware of three “field study” campaigns in the gene ral Denver area during 2006 that provides additional data to evaluate the modeling system:

• The CDPHE/APCD collected VOC samples duri ng 2006 that will assist in evaluating this important ozone precursor. Most VOC sample s were collected in the morning (6-9am MDT) with samples for the following sites av ailable during some days of the June-July 2006 modeling episode:

• CAMP

• Welby

• Fort Lupton

• Platteville

• Rocky Flats North

• Fort Collins West

• During portions of the 2006 episode (end of July), NOAA launched daily ozonesondes at numerous sites throughout the U.S., including Boulder. The ozonesonde measurements will provide valuable information on the vertical structure of ozone concentrations, including the potential identificatio n of an ozone reservoir aloft.

• Finally, the NPS and CDPHE collected specia l measurements as part of the ROMANS study during 2006.

The comparisons against these field study data are done in the Chapter 3 diagnostic evaluation

section.

2.1.2.2 Model Performance Goals and Criteria

As discussed in the Denver Modeling Protocol (Morris et al., 2007) and preliminary model performance evaluation (Morris et al., 2008b), we are using seve ral model performance goals and criteria based on EPA guidance documents a nd past studies to assi st in gauging the 2006 base case model performance. The model perfor mance goals and criteria are not meant to be pass/fail tests, but rather to help frame the model performance and put it into contact. EPA’s 1- hour ozone modeling guidance presented three m odel performance goals for hourly ozone that

are listed in Table 2-2.

Table 2-2. EPA’s 1-hour ozone performance goals (EPA, 1991).

Performance Statistics Performance Goal Unpaired Peak Accuracy <±20%

Mean Normalized Bias <±15%

Mean Normalized Gross Error <35%



### EPA’s 1999 draft 8-hour ozone mo deling guidance presented a useful performance goal that compares the observed daily maximum 8-hour ozone concentrations with modeled values “near the monitor”, with the goal being that most of the observed and modeled value near the monitor pairs be within ±20% of each other. This perf ormance goal is particularly relevant because theF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-5 modeled daily maximum 8-hour ozone concentrations near the monitor are the very values used in making the 8-hour ozone projections. As used in the Denver EAC SIP (Morris et al., 2003), we have developed three approach es for defining “near the monitor”. For two of the approaches

we define “near” as the same NX by NY array of cells centered on the monitor as used in EPA’s 8-hour ozone attainment test (e.g., 7 x 7 for 4-5 km grid) and the two tests differ in only which estimated value is selected from this array of ce lls. For the third test, we select the estimated value at the monitor (i.e., spatially paired). The three methods for defining “near the monitor”

are as follows:

Maximum : Select the maximum estimated daily maximum 8-hour ozone concentration near the ozone monitor for each day. This is the same approach used in EPA’s 8-hour

ozone attainment test.

Closest : Select the estimated 8-hour ozone concen trations near the monitor that matches

the observed value best.

Spatially Paired : Select the estimated 8-hour ozone concentrations at the monitoring

location.

Table 2-3 summarizes the performance goal fo r daily maximum 8-hour ozone concentrations using these three approaches for “near the monitor”.

Table 2-3. 8-hour ozone model performance goal co mparing observed daily maximum 8-hour ozone concentrations with predicted values “near the monitor” (EPA, 1999).

“Near The Monitor” Threshold Goal

Maximum modeled daily maximum 8-hour ozone concentrations within a 7 x 7 array of 4 km grid cells around

monitor <±20% Most pairs within ±20%

Closest modeled daily maximum 8-hour ozone concentrations within a 7 x 7 array of 4 km grid cells around monitor to the

observed value at the monitor. <±20% Most pairs within ±20%

Spatially Paired modeled daily maximum 8-hour ozone concentration at the location of the monitoring site <±20% Most pairs within ±20%



### For PM species, several of the RPOs conducti ng regional haze modeling have adopted three levels of model performance goals and criteria for PM species fr actional bias and gross error as

listed in Table 2-4. Note that we are not suggesting that these performance goals be adopted as guidance. Rather, we are just using them to frame and put the PM model performance into context and to facilitate model performance inte rcomparison across episodes, species, models, sensitivity tests and studies.

Table 2-4. Model performance goals and criteria for components of fine particle mass.

Fractional Bias Fractional Error Comment

< 15% < 35% Goal for PM model performance based on ozone model performance, considered excellent performance

< 30% < 50% Goal for PM model performance, considered good performance

< 60% < 75% Criteria for PM model performance, considered average performance. Exceeding this level of performance indicates fundamental concerns with the modeling system and triggers diagnostic evaluation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-6 The above performance statistics are based use the Unpaired Peak Accuracy and normalized and fractional bias and gross error me trics. These statistical performance metrics are defined in

Table 2-5.

Table 2-5. Definitions of statistical performance measures used in the model evaluation.

Statistical

Measure Shorthand
Notation Mathematical Expression Notes

Accuracy of

Paired Peak A p

peak peak


### O O P

− Predicted value P is located at same monitor as observed peak

Unpaired Peak Accurcay UPA

peak peak


### O O P

− Predicted value P taken as the unpaired maximum anywhere in the local region

Mean Fractional
Error MFE 

# ∑

= 

### + − N

i i i i i 

### O P O P

N 1 

### 2 Reported as %

Mean Absolute
Gross Error MAGE 

# ∑

= 

### − N

i i i 

### O P N 1 

### 1

Mean
Normalized
Gross Error MNGE 

# ∑

= 

### − N

i i i i


### O O P

N 1 

### 1 Reported as %

Mean Bias MB 

# ( ) 

# ∑

= 

### − N

i i i 

### O P N 1 

### 1 Reported as concentration

Mean
Normalized Bias MNB 

## ( ) 

# ∑

= 

### − N

i i i i 

### O O P

N 1 

### 1 Reported as %

Mean
Fractionalized
Bias (Fractional Bias) MFB 

# ∑

= 

### ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

+ − N

i i i i i 

### O P O P

N 1 

### 2 Reported as %



### 2.2 OVERVIEW OF MODEL PERFORMANCE EVALUATION APPROACH



### The model performance evaluation of the fina l CAMx Run 17 2006 base case simulation of the June-July 2006 Denver ozone episode makes use of graphical, statistical and diagnostic evaluation tools. We first presen t a series of standard ozone m odel performance statistics for the entire June-July 2006 episode and compare them with the performance goals. Although such comparisons are not a comprehensive evaluation, they do identify if something is greatly wrong and provide a context for comparison model perfo rmance with other studies. The general CAMx ozone model performance over the en tire episode is then discussed.

We then focus on the ozone model performa nce for three 3-day episodes when observed

exceedances of the 8-hour ozone st andard occurred in the Denver NAA. The details of the ozone model performance for these 3-day episodes are pr esented. Figure 2-2 displays the region-wide maximum 8-hour ozone concentration in the Denver NAA for the June-July 2006 modeling period, with the three 3-day episodes selected for more detailed analysis indicated by the red dotted lines at the 85 ppb ozone NAAQS level. These three 3-day episodes include 7 of the 9 8- hour ozone exceedance days during the June-J uly 2006 modeling period and are as follows:

• June 17-19, 2006F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-7 • July 13-15, 2006

• July 27-29, 2006

Figure 2-2 . Maximum daily maximum 8-hour ozone concentration (ppb) observed during the June-July 2006 episode and three “mini episodes” selected for more detailed analysis: June17- 19, July 13-15, and July 27-29.



### 2.3 OPERATIONAL OZONE MODEL PERF ORMANCE FOR THE JUNE-JULY

2006 MODELING PERIOD



### Figures 2-3 and 2-4 display the daily ozone m odeling performance stat istical metrics during June-July 2006 and the final CAMx Run 17 2006 ba se case simulation for, respectively, 1-hour

and 8-hour ozone concentrations in the Denve r NAA, and compares them with EPA’s 1-hour ozone performance goals for Unpaired Peak Accuracy ( ≤ ±20%), Mean Normalized Bias ( ≤ ±15%) and Mean Normalized Gross Error ( ≤ 35%). EPA (1991) developed these ozone statistical performance goals for 1-hour ozone, bu t we have also applied them for 8-hour ozone performance for testing purposes as well. Th e ozone statistical perf ormance measures are calculated using all ozone predicted and observed pairs (matched by time and location) for which the observed values is greater than a threshold values; a 60 ppb and 40 ppb observed threshold

value was used for the 1-hour and 8-hour oz one performance measures, respectively.

There are five panels of daily ozone model performance presented in these figures for the JuneJuly 2006 modeling period. The top panel presen ts the observed region -wide daily maximum 8- hour ozone concentration and the predic ted value that is spatially paired at the same site. Not surprising, the modeled predicted daily maximum 8-hour ozone concentrations at the site with the observed maximum is almost always lower. The second panel presents the Unpaired Peak Accuracy metric and compares it to the ≤ ±20% EPA performance goal. The third panel is the Average Peak Paired Accuracy which is essentia lly the Normalized Mean Bias of predicted and observed daily maximum 8-hour ozone concentrations paired at each monito ring site. The fourth and fifth panels show the normalized bias and gro ss error statistical performance metrics that are compared to EPA’s ≤ ±15% and ≤ 35% performance goa ls, respectively.

2.3.1 Ozone Performance Stat istics for 1-Hour Ozone Denver Highest Observed 8-Hour Ozone during June-July 2006

50 55 60 65 70 75 80 85 90 95 1001-Jun-063-Jun-065-Jun-067-Jun-069-Jun-0611-Jun-0613-Jun-0615-Jun-0617-Jun-0619-Jun-0621-Jun-0623-Jun-0625-Jun-0627-Jun-0629-Jun-061-Jul-063-Jul-065-Jul-067-Jul-069-Jul-0611-Jul-0613-Jul-0615-Jul-0617-Jul-0619-Jul-0621-Jul-0623-Jul-0625-Jul-0627-Jul-0629-Jul-0631-Jul-06 Ozone (ppb) 1st

DateF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-8 The 1-hour ozone Unpaired Peak Accura cy performance metric achieves the ≤ ±20% performance goal for all days of the June-July 2006 modeling peri od except two days (second to top time series in Figure 2-3). On June 19, 2008 the modeled region-wide maximum 8-hour

ozone concentrations is -20.8% below the obser ved value so just barely does not meet EPA’s

≤ ±20% performance goal. And on July 24, 2006, the 1-hour ozone Unpaired Peak Accuracy is 22.9% that slight ly exceeds the ≤ ±20% performance goal. The modeled unpaired peak on this day occurs to the southeast of Denver (see Appe ndix A) where no monitors exist so the presence of this higher modeled value can not be verified by the current monitoring network in the Denver NAA. In fact, more than two thirds of the tim e (73% of the days) the 1-hour ozone Unpaired Peak Accuracy metric ach ieves a more stringent ≤ ±10% performance goal (that is the final CAMx 2006 base case simulation modeled peak 1-hour ozone concentrations in the Denver NAA is within 10% of the observed peak on a va st majority of the days during the June-July 2006 modeling period).

The third daily time series panel in Figure 2-3 presents the 1-hour ozone Average Accuracy of the Peak performance measure. This is the Mean Normalized Bias for daily maximum 1-hour

ozone concentrations across all sites in the Denver NAA matched by loca tion and day (but may not match by time of day). There is no performan ce goal for this metric, but it appears most days during the June-July 2006 mode ling period are within ±20%.

The bottom two panels in Figure 2-3 displays the daily Mean Normalized Bias and Mean Normalized Gross Error performance metrics fo r 1-hour ozone for which EPA has performance goals of within ≤ ±15% and ≤ 35%, respectively. The Mean Normalized Gross Error always

achieves the ≤ 35% performance goal and, in fact, is always ≤ 20% and frequently ≤ 10%. These are quite good performance metrics for Mean Normalized Gross Error.

Of the 30 days during June 2006, 26 days achieve the <±15% performance goal for 1-hour ozone Normalized Bias (i.e., 87 perc ent of the days in June 2006 achieve the 1-hour ozone bias performance goal). Of the four days in June th at do not achieve the bias performance goal, three are due to an underprediction bias of -16.8% (J une 13), -17.2% (June 17) and -16.4% (June 24) and one is due to an overpredicti on bias of 18.1% (June 28).

The 1-hour ozone Mean Normalized Bias metrics fo r June are fairly balanced with days of both underprediction and overprediction bias (Figure 2-3a). However, in July a normalized bias undeprediction occurs on most days. Even with th is underprediction bias in July, of the 28 days with normalized bias metrics, 24 days (86% ) had normalized bias that achieves EPA’s ≤ ±15% performance goal. Note that normalized bias values were not calculated for July 8-9, 2006 because there were no observed hourly ozone concentrations above the 60 ppb threshold and July

31 st 

### was also missing because it was not simulated for the full day because it was at the end of the episode and meteorological data for the e nd of the day were not available due to the conversion from GMT to MST time; besides it was a low ozone day (all observed ozone < 70 ppb) so would not provide any additional data fo r the Design Value projections. The normalized bias on July 10, 13, 22 and 23 did not achieve the 1-hour ozone performance goal for normalized bias with normalized bias values of, respectiv ely, -19.7%, -18.1%, -1 7.95% and -19.7%. The July 10 th 

### poor performance is not a concern since th is is a low observed and modeled ozone day, however July 13, 22 and 23 are observed ozone exceedance or near exceedance days so the underprediction bias is a concern.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-9 Denver Run17 2006 Base Case 1hr O3

Unpaired Peak Accuracy

-30 -20 -10

0 10 20 306/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

+20%

-20%

Average Paired Peak Accuracy

-30 -20 -10

0 10 20 306/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

Normalized Bias

-30 -20 -10

0 10 20 306/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

+15%

-15%

Normalized Error

0 10 20 30 406/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

35% Peak Observed and Paired Predicted

0 20 40 60 80 100 120 1406/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(ppb) Observed

Run17

120 ppb



### Figure 2-3a. Daily ozone model performance evaluation statistical performance measures in the Denver NAA and comparison with EPA performance goals for June 2006, the final CAMx
Run17 2006 base case simulation and 1-hour ozone.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-10 Denver Run 17 2006 Base Case 1hr O3

Unpaired Peak Accuracy

-30 -20 -10

0 10 20 307/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

+20%

-20%

Average Paired Peak Accuracy

-30 -20 -10

0 10 20 307/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

Normalized Bias

-30 -20 -10

0 10 20 307/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

+15%

-15%

Normalized Error

0 10 20 30 407/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%)

Run17

35% Peak Observed and Paired Predicted

0 20 40 60 80 100 120 1407/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(ppb) Observed

Run17

120 ppb



### Figure 2-3b. Daily ozone model performance evaluation statistical performance measures in the Denver NAA and comparison with EPA perfo rmance goals for July 2006, the final CAMx
Run17 2006 base case simulation and 1-hour ozone.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-11 2.3.2 Daily Ozone Performance Statistics for 8-Hour Ozone Concentrations



### Figure 2-4 displays the same daily statistical performance metric time series for running 8-hour

ozone concentrations as shown for 1-hour ozone in Figure 2-3, only using a 40 ppb observed ozone cutoff instead of 60 ppb as used for the 1-hour ozone metrics. Al so shown in Figure 2-4 are EPA’s 1-hour ozone performance goals for U npaired Peak Accuracy and Mean Normalized Bias and Gross Error that are compared to th e 8-hour ozone statistics for reference. The Unpaired Peak Accuracy measur e for 8-hour ozone achieves the ≤ ±20% performance goal on 27 of the 30 days (90% of the days) in June (Figur e 2-4a). On June 19, 22 and 28 the 8-hour ozone Unpaired Peak Accuracy performance statistics were -23.8%, +20.6% and +26.1%, respectively. On June 19, 2006, the model predicts relative ly low ozone (50-75 ppb) throughout the domain and completely fails to capture the observe d ozone exceedances at RFNO (95 ppb), FTCW (88 ppb) and SBC (87 ppb). June 19, 2006 is a ve ry poor performing day for the model. An examination of the maps comparing the predicte d and observed spatial di stribution of the 8-hour ozone concentrations on June 22, 2006 (Appendix A) reveals that there is a predicted cloud of

elevated 8-hour ozone concentrations of 75- 80 ppb that occurs south of Denver between the monitors in the DMA and Colorado Springs. W ithin the DMA, both the observed and modeled 8-hour ozone concentrations are between ~40 ppb and ~60 ppb. On June 28 the modeled 8-hour ozone peak is 86 ppb and occurs southeast of the DMA away fr om the ozone monitors; again within the DMA itself there is reasonable agreem ent between the predicted and observed daily

maximum 8-hour ozone concentrations. The mode led high ozone southeas t of the DMA is not supported by the observations in Colorado Springs , but its presence can not be confirmed or refuted by the current DMA ozone monitoring ne twork. During July 2006, the CAMx Run 17

2006 base case simulations achieves EPA’s ≤ ±20% performance goal on all 30 days of the month (Figure 2-4b).

With the exception of an overprediction bias on June 16 and 28, the Av erage Accuracy of the Peak performance metrics are less than ±20% for 28 days in June and less than ±20% for all 30 days in July (Figure 2-4). The 8-hour ozone Mean Normalized Bias values in June 2006 are characterized by an overp rediction bias with 11 days exceeding the ≤ ±15% 1-hour performance goal. An examination of the time series plots of hourly ozone in Appendix C reveals that this overprediction bias is mainly due to overestim ation of the nighttime low hourly ozone values.

Unlike for 1-hour ozone performance statistics, wh ere June was performing better than July, for the 8-hour ozone performance statistics July is pe rforming better (Figure 2- 4b) than June (Figure 2-4a). All days in July the 8-hour ozone Unpaired Peak Accuracy meets the ≤ ±20% performance goal. With the exception of Ju ly 3 (+16.3%) and 12 (+16.2%) ove r 90% of the days in July

exhibit normalized bias values for 8-hour ozone concentrations that achieve the ≤ ±15% 1-hour performance goal. As for June, all days achie ve the gross error perf ormance goal by a wide margin.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-12 Denver Run 17 2006 Base Case 8hr O3

Unpaired Peak Accuracy

-30 -20 -10

0 10 20 306/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

+20%

-20%

Average Paired Peak Accuracy

-30 -20 -10

0 10 20 306/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

Normalized Bias

-30 -20 -10

0 10 20 306/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

+15%

-15%

Normalized Error

0 10 20 30 406/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

35% Peak Observed and Paired Predicted

50 60 70 80 90 1006/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(ppb) Observed

Run17

85 ppb



### Figure 2-4a. Daily ozone model performance evaluation statistical performance measures in the Denver NAA and comparison with EPA performance goals for June 2006, the final CAMx
Run17 2006 base case simulation and 8-hour ozone.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-13 Denver Run 17 2006 Base Case 8hr O3

Unpaired Peak Accuracy

-30 -20 -10

0 10 20 307/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

+20%

-20%

Average Paired Peak Accuracy

-30 -20 -10

0 10 20 307/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

Normalized Bias

-30 -20 -10

0 10 20 307/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

+15%

-15%

Normalized Error

0 10 20 30 407/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

35% Peak Observed and Paired Predicted

0 20 40 60 80 100 1207/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(ppb) Observed

Run17

85 ppb



### Figure 2-4b. Daily ozone model performance evaluation statistical performance measures in the Denver NAA and comparison with EPA perfo rmance goals for July 2006, the final CAMx
Run17 2006 base case simulation and 8-hour ozone.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-14 2.3.3 Daily Maximum 8-Hour Ozone Performance



### The Unpaired Peak Accuracy performance metr ic compares the daily maximum observed ozone at any site in the Denver m onitoring network with the model predicted maximum ozone anywhere within the Denver subreg ion (Figure 2-1). This is metric is somewhat biased because the monitoring network represents a limited spatia l extent that may not record the actual daily maximum ozone concentration on that day, wher eas the model has pred ictions throughout the region whose maximum may not occur at the locations of a monitor. In this case, a “perfect model” could exhibit an overprediction bias for th is metric just because the modeled ozone peak occurs away from the monitoring sites. Thus, in this section we examin e predicted and observed spatial paired daily maximum 8-hour ozone metrics, which is a particular ly stringent test of model performance.

Figure 2-5 displays the highest observed daily maximum 8-hour ozone concentration at any monitoring in the Denver network along with the spatially paired predicted daily maximum 8-

hour ozone concentration at the same monito r. The modeled daily maximum 8-hour ozone concentration at the site with the highest obser ved value tends to follow the observed day-to-day variations quite well, but it usually has an underp rediction bias especially on the highest days. This is not surprising as small spatial displacement in the winds may slightly miss-locate an urban ozone plume so that it does not directly impact the ozone monitor. EPA accounts for such spatial displacements of the modeled peak from the observed peak in their attainment demonstration test by using the highest modele d 8-hour ozone near the ozone monitor, where near is defined as approximately within appr oximately 15 km. Thus, for making 8-hour ozone projections at a monitor EPA guidance recomm ends selecting the hi ghest modeled daily

maximum 8-hour ozone concentration from a 7 x 7 array of 4 km grid cells centered on the monitoring site (EPA, 2007).F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-15 Peak Observed 8-Hour Ozone and Paired Predicted

50 55 60 65 70 75 80 85 90 95 1006/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(ppb) Observed Run17

Peak Observed 8-Hour Ozone and Paired Predicted

50 55 60 65 70 75 80 85 90 95 1007/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(ppb) Observed Run17



### Figure 2-5. Compared of observed highest daily maximum 8-hour ozone concentration for each day during June (top) and July (bottom) 2006 with concurrent spatially paired prediction
from the CAMx Run 17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-16 As noted above, EPA’s draft 8-hour ozone m odeling guidance listed a performance goal for predicted daily maximum 8-hour ozone concentrati ons near a monitor of within ±20% for most of the monitor-days (EPA, 1999). By near the m onitor we have presente d three approaches (see Table 2-3) for selecting the modeled daily maxi mum 8-hour ozone concentra tion to pair with the observed value, the Maximum and Closest value with in a 7 x 7 array of 4 km grid cells centered

on the monitor and selection of the modeled valu e at the monitor location (Spatially Paired).

Figure 2-6 and Table 2-6 present the results of the comparisons of predicted and observed daily maximum 8-hour ozone concentrations and compares them with the ≤ ±20% performance goal. Using the closest modeled daily maximum 8-hour ozone concentration near the monitor to the observed value, 89% of the daily maximum 8-hour ozone concentrations prediction and observed monitor-days are within ±20% of each other. And when comparing predicted/observed daily

maximum 8-hour ozone concentrations co-located at the monitor, 82% of the monitor-day pairs are within ±20% of each other. Thus, the CA Mx Run 17 2006 base case simulation satisfies the performance goal from EPA’s 1999 draft 8-hour oz one modeling guidance that most predicted daily maximum 8-hour ozone monitor-days be within ±20% of the observed value.

Table 2-6. Percent of the monitor-days that the model predicted daily maximum 8-hour ozone
concentrations near the monitor is within ±20% of the observed value (total monitor-days = 1008).

Maximum Near the Monitor Percent Difference # Days % Days

<-20 9 1%

-20% to +20 769 76%

> +20 230 23%

Closest Near the Monitor Percent Difference # days %

<-20 23 2%

-20% to +20 902 89%

> +20 83 8%

Co-Located At the Monitor Percent Difference # days %

<-20 48 5%

-20% to +20 829 82%

> +20 131 13%F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-17 Daily maximum 8-Hour ozone near monitor. All sites & all days. Subregion = Denver June+July, 2006. Run17 04km

0 20 40 60 80 100 120

0 20 40 60 80 100 120

Observed Ozone (ppb)Predicted Ozone (ppb) r 2 =0.2032

O - - O shows quantiles



### Figure 2-6a. Comparison of predicted and observed daily maximum 8-hour ozone concentrations for the June-July 2006 modeling period and the final CAMx Run 17 2006 base case simulation using the Maximum predicted value near the monitor.

Nearest daily maximum 8-Hour ozone. All sites & all days. Subregion = Denver June+July, 2006. Run17 04km

0 20 40 60 80 100 120

0 20 40 60 80 100 120

Observed Ozone (ppb)Predicted Ozone (ppb) r 2 =0.61

O - - O shows quantiles



### Figure 2-6b. Comparison of predicted and observed daily maximum 8-hour ozone concentrations for the June-July 2006 modeling period and the final CAMx Run 17 2006 base case simulation using the Closest predicted value near the monitor.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-18 Daily maximum 8-Hour ozone at monitor. All sites & all days. Subregion = Denver June+July, 2006. Run17 04km

0 20 40 60 80 100 120

0 20 40 60 80 100 120

Observed Ozone (ppb)Predicted Ozone (ppb) 

### r 2 

### =0.2615

O - - O shows quantiles



### Figure 2-6c. Comparison of predicted and observed daily maximum 8-hour ozone concentrations for the June-July 2006 modeling period and the final CAMx Run 17 2006 base case simulation using the Co-Located predicted value near the monitor.



### 2.4 DETAILED PERFORMANCE FOR THREE 3-DAY EPISODES



### In this section we perform a more detailed oz one model performance evaluation for three 3-day episode that occurred during the June-July 2006 modeling period. During these three 3-day episodes, 7 of the 9 8-hour ozone exceedance days from June-July 2006 modeling period occurred. This episodic ozone model perf ormance evaluation makes use of performance statistics, spatial maps and time series plots that are provided for the entire June-July 2006 modeling period in Appendices B and C.

2.4.1 June 17-19, 2007



### The first 3-day episode examined is the J une 17-19, 2006 episode during which 8-hour ozone exceedances occurred at the RFNO (94 ppb), SOBC (87 ppb) and FTCW (87 ppb) monitoring

sites on June 19. Elevated ozone also occurred at the Chatfield site ( 81 ppb) on June 17, and

numerous monitors measured 8- hour ozone concentrations in ex cess of 70 ppb during this 3-day episode. Table 2-7 compares the ozone model performance statistical measures with EPA’s goals (EPA, 1991) for monitoring sites in the DM A and vicinity and the three episode days. With the exception of 1-hour ozone normalized bias on June 17 (-17.2%) and unpaired peak accuracy on June 19 for 1-hour (-20.8%) and 8-h our (-23.8%) ozone, all of the ozone modeling performance statistics achieve EPA’s goals. Ho wever, there is a consistent and pronounced underprediction bias in the ozone performance statistics.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-19 Table 2-7. Final CAMx Run 17 2006 base case simulation daily 1-hour and 8-hour statistical performance measures for the June 17-19, 2006 episode and comparison with EPA performance goals.

2006 Performance
Statistic EPA
Goal June 17 June 18 June 19

1-Hour Ozone Unpaired Peak ≤ ±20% -17.2 -2.2 -20.8

Normalized Bias ≤ ±15% -17.2 -13.0 -11.9

Normalized Error ≤ 35% 17.3 13.0 15.9

8-Hour Ozone Unpaired Peak ≤ ±20% -15.0 -8.9 -23.8

Normalized Bias ≤ ±15% -6.1 -1.3 2.1

Normalized Error ≤ 35% 12.4 12.1 17.5



### Figures 2-7 display the spatial distribution of the predicted an d observed daily maximum 8-hour ozone concentrations on July 17-19, 2006 and the preliminary CAMx (Run1.1204) base case simulation. The spatial distri bution of the modeled daily maxi mum 8-hour ozone concentrations

on June 17 th 

### are extremely flat, ranging from 50 to 70 ppb (Figure 2-7a). This is compared to observed values that are also fairly flat, but a bout 10 ppb higher, ranging from 67 to 81 ppb. At the Chatfield and Highland monitors, where the hi ghest observed values o ccur on this day (80-81 ppb), the model is predicting less than 70 ppb (60-70 ppb).

On June 18 th 

### the variations in spatial distribution of the modeled (50-70 ppb) and observed (63- 76 ppb) daily maximum 8-hour ozone concentrations were both fairly flat, with the modeled values lower than observed (Figure 2-7b).

On the June 19 th 

### , the 8-hour ozone exceedance day for this 3-day episode, both the modeled and

observed 8-hour ozone concentratio ns are higher. The model co rrectly simulates the observed slightly elevated daily maximum 8-hour ozone c oncentrations at the s outhern ozone monitors (74-76 ppb at CHAT and HIGH). However, the hi ghest observed 8-hour ozone concentrations at RFNO (95 ppb) is underpredicted by the mode l by approximately 20 ppb, as is the ozone exceedance at FCTW (88 ppb).

Time series of predicted and observed hourly ozone concentrations for the June 17-19, 2006 period and several key monitoring s ites are shown in Figure 2-8. The modeled diurnal variations of the hourly ozone concentrations at the AR VA and NREL sites northwest of Denver are much flatter than the observed values. There are night time ozone increases in both the modeled and

observed ozone concentrations. At ARVA the m odel fails to capture the observed daytime peaks and nighttime lows, and at NREL the nighttime lo ws are captured, but the daytime peaks are underestimated. The underpredi ction of the daytime peaks is also apparent at the RFNO monitoring site, particular on the June 19 th 

### exceedance day. At RFNO, the modeled ozone increase begins to rise with the observed values at 9am, but flattens out at under 80 ppb at 11am as the observed values keep on rising to over 100 ppb. This may be due to too fast rise of the modeled mixing heights, a failure to capture a subs idence inversion and/or failure of the model to capture high ozone aloft.

At two sites south of Denver (CHAT and HIGH) the observed daytime peaks are underestimated on June 17-18, but reproduced quite well on June 19 th 

### . The nighttime lows are represented reasonably well at these two sites. Similar result s are seen at the two Fort Collins sites north ofF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-20 Denver with the modeled daytime peaks underestim ated by the model. The model does identify

June 19 th 

### as the worst ozone day, but ozone formation at the Fort Collins sites is too slow and peaks15-20 ppb below the observed ozone peaks.

Figure 2-9 displays the predicte d and observed hourly time se ries plots for NOx (top), CO (middle) and ozone (bottom) for two sites in downtown Denver, WELB and CAMP. At WELB the model is estimating higher daytime NOx than observed. At CAMP, the model matches the

diurnal variations of the observed NOx concentr ations reasonably well, suggesting that the

mobile source NOx emissions in downtown Denver are reasonably well characterized.

Figure 2-7a. Spatial distribution of the predicted and observed daily maximum 8-hour ozone concentrations (ppb) in the Denver area on July 17, 2006 for the final CAMx Run 17 2006 base

case simulation



### .F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-21 Figure 2-7b. Spatial distribution of the predicted and observed daily maximum 8-hour ozone concentrations (ppb) in the Denver area on July 18, 2006 for the final CAMx Run 17 2006 base

case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-22 Figure 2-7c. Spatial distribution of the predicted and observed daily maximum 8-hour ozone concentrations (ppb) in the Denver area on July 19, 2006 for the final CAMx Run 17 2006 base

case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-23 

## ARVA: Arvada -687.213 8.568

0 10 20 30 40 50 60 70 80 90 100 110 120



### 6/17/ 6 6/18/ 6 6/19/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



## NREL: National Renewable E -694.376 2.926

0 10 20 30 40 50 60 70 80 90 100 110 120



### 6/17/ 6 6/18/ 6 6/19/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed PredictedF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-24 

## RFNO: Rocky Flats North -693.592 21.629

0 10 20 30 40 50 60 70 80 90 100 110 120



### 6/17/ 6 6/18/ 6 6/19/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



## CHAT: Chatfield -687.313 -20.937

0 10 20 30 40 50 60 70 80 90 100 110 120



### 6/17/ 6 6/18/ 6 6/19/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed PredictedF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-25 

## HIGH: Littleton -677.368 -18.104

0 10 20 30 40 50 60 70 80 90 100 110 120



### 6/17/ 6 6/18/ 6 6/19/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



## FTCW: Fort Collins West -682.854 96.141

0 10 20 30 40 50 60 70 80 90 100 110 120



### 6/17/ 6 6/18/ 6 6/19/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed PredictedF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-26 

## FTCO: Fort Collins South -677.801 94.012

0 10 20 30 40 50 60 70 80 90 100 110 120



### 6/17/ 6 6/18/ 6 6/19/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure 2-8. Time series of predicted and observed hourly ozone concentrations (ppb) during June 17-19, 2006 for the final CAMx Run 17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-27 80013001: Welby -674.141 11.613

0 30 60 90 120 150

6/17/ 6 6/18/ 6 6/19/ 6 DateNOX [ppb] Minimum to Maximum Range Observed Predicted

80013001: Welby -674.141 11.613

0 200 400 600 800 1000 1200 1400 1600 1800 2000

6/17/ 6 6/18/ 6 6/19/ 6

DateCO [ppb] Minimum to Maximum Range Observed Predicted

WELB: Welby -674.141 11.613

0 10 20 30 40 50 60 70 80 90 100 110 120

6/17/ 6 6/18/ 6 6/19/ 6

DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure 2-9a. Comparison of hourly NOx (top), CO (middle) and ozone (bottom) predicted and observed time series at the Welby monitoring site for June 17-19, 2006 and the final CAMx

Run17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-28 80310002: CAMP -678.182 2.310

0 30 60 90 120 150

6/17/ 6 6/18/ 6 6/19/ 6 DateNOX [ppb] Minimum to Maximum Range Observed Predicted

80310002: CAMP -678.182 2.310

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

6/17/ 6 6/18/ 6 6/19/ 6

DateCO [ppb] Minimum to Maximum Range Observed Predicted

CAMP: 2105 Broadway -678.182 2.310

0 10 20 30 40 50 60 70 80 90 100 110 120

6/17/ 6 6/18/ 6 6/19/ 6

DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure 2-9b. Comparison of hourly NOx (top) and ozone (bottom) predicted and observed time series at the CAMP monitoring site for June 17-19, 2006 and the preliminary CAMx Run17 2006

base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-29 2.4.2 July 13-15, 2006



### The July 13-15, 2006 episode was a very severe 3-day ozone episode in the DMA with 11

instances of monitors exceed ing the 85 ppb 8-hour ozone NAAQS and with two exceedance days each at the SOBC, RFNO and FC TW monitoring sites. Table 2-8 summarizes the 1-hour and 8- hour ozone performance statistics for this 3- day episode. Although there is a large ozone underprediction bias on July 13 th



### , so that the EPA normalized bias goal is not achieved, performance on July 14-15 is better achieving EPA’s performance goals for all metrics.

Table 2-8. Final CAMx Run 17 2006 base case simulation daily 1-hour and 8-hour statistical performance measures for the July 13-15, 2006 episode and comparison with EPA performance goals.

2006

Performance
Statistic EPA
Goal July 13 July 14 July 15

1-Hour Ozone Unpaired Peak ≤ ±20% -18.6 -0.3 -7.6

Normalized Bias ≤ ±15% -181 -12.7 -5.3

Normalized Error ≤ 35% 18.1 13.4 9.8

8-Hour Ozone Unpaired Peak ≤ ±20% -18.5 -9.5 -6.5

Normalized Bias ≤ ±15% -6.1 -6.4 7.7

Normalized Error ≤ 35% 14.8 13.3 12.7



### The poor performance on July 13 th 

### is also reflected in the comparisons of the spatial distribution of the observed and predicted daily maximum 8-hour ozone concentrations in Figure 2-10a. The high observed ozone at the monitoring sites s outh of Denver (86-92 ppb) is underpredicted by the model by approximately 20 ppb.

Better performance is seen on July 14, 2006 (Figur e 2-10b). The model correctly places a large expanse of elevated ozone concentrations stretc hing from northwest Denver to Fort Collins that also impacts the Niwot Ridge and RMNP sites where ozone exceedances are observed (91 ppb). The modeled ozone peak (88 ppb) is located very close to the monitored ozone peak (97 ppb) at FTCW monitoring site. If the modeled ozone was about 10 ppb higher and extended a little further west, model performance wo uld be excellent on this day.

On July 15th the modeled elevated ozone cloud is located to the northeas t of Denver, when it should be located to the northwest of the city. Th is is clearly a case of spatial displacement due to errors in the wind fields (Figure 2-10c).F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-30 Figure 2-10a. Spatial distribution of the predicted and observed daily maximum 8-hour ozone concentrations (ppb) in the Denver area on July 13, 2006 for the final CAMx Run 17 2006 base

case simulation



### .F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-31 Figure 2-10b. Spatial distribution of the predicted and observed daily maximum 8-hour ozone concentrations (ppb) in the Denver area on July 14, 2006 for the final CAMx Run 17 2006 base

case simulation



### .F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-32 Figure 2-10c. Spatial distribution of the predicted and observed daily maximum 8-hour ozone concentrations (ppb) in the Denver area on July 15, 2006 for the final CAMx Run 17 2006 base

case simulation



### .F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-33 The time series of predicted and observed hourly ozone concentrations for the July 13-15, 2006 3-day episode are shown in Figure 2-11. Th e model does a better job of reproducing the observed diurnal variation of the observed hourly concentrations at the ARVA and NREL sites just northwest of Denver on July 13-15 than the June 17-19 episode, but still shaves the observed daytime ozone peaks. The 8-hour ozone exceed ances at the RFNO monitor on July 14-15 are underestimated by over 20 ppb.

The modeled ozone at RMNP is nearly constant 60 ppb except for a 20 ppb increase on July 14 to 80 ppb. The observed values are more variab le (typically 50 ppb to 70 ppb) and also exhibit an increase on July 14 th 

### that is twice as high (40 ppb) as the modeled increase (20 ppb). As noted in the spatial comparisons in Figure 2-10b) , the modeled elevated ozone cloud is displaced slightly eastward. This is a fairly common attrib ute of the MM5 winds inability to fully simulate the upslope flows during the day.

Ozone model performance at the monitoring site s south of Denver (WELC, CHAT and HIGH) is quite good on July 14-15, with the observed da ytime ozone underestimated on July 13.

At the monitoring sites north of Denver (F TCO, FTCW and WCTO), daytime ozone is underestimated on July13th at a ll three monitors with better performance seen on July 14-15, albeit with a daytime underestimation bias.

Figure 2-12 compares the predicted and observed hourly NOx, CO and ozone concentrations at

the WELB and CAMP central Denver sites. At these sites the NOx, CO and ozone concentrations are reproduced quite well, with daytime modeled NOx values higher than observed at WELB, but matched qu ite well at CAMP. As NOx and CO at these two sites will be dominated by on-road mobile source emissions, th ese results suggest that the on-road mobile source NOx and CO emissions are reasonably well characterized.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-34 

## NREL: National Renewable E -694.376 2.926

0 10 20 30 40 50 60 70 80 90 100 110 120



### 7/13/ 6 7/14/ 6 7/15/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### ARVA: Arvada -687.213 8.568

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed PredictedF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-35 RFNO: Rocky Flats North -693.592 21.629

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### RMNP: Rocky Mountain NP -719.909 64.528

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed PredictedF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-36 WELC: Welch -692.154 -8.925

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### HIGH: Littleton -677.368 -18.104

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed PredictedF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-37 CHAT: Chatfield -687.313 -20.937

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### FTCO: Fort Collins South -677.801 94.012

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed PredictedF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-38 FTCW: Fort Collins West -682.854 96.141

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### WCTO: Weld County Tower -651.000 70.457

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure 2-11. Hourly time series of predicted and observed hourly ozone concentrations for the July 13-15, 2006 period and the final CAMx Run17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-39 80013001: Welby -674.141 11.613

0 50 100 150 200

7/13/ 6 7/14/ 6 7/15/ 6 DateNOX [ppb] Minimum to Maximum Range Observed Predicted

80013001: Welby -674.141 11.613

0 200 400 600 800 1000 1200 1400 1600 1800 2000

7/13/ 6 7/14/ 6 7/15/ 6

DateCO [ppb] Minimum to Maximum Range Observed Predicted

WELB: Welby -674.141 11.613

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6

DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure 2-12a. Comparison of hourly NOx (top) and ozone (bottom) predicted and observed time series at the Welby monitoring site for July 13-15, 2006 and the final CAMx Run17 2006

base case simulation base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-40 80310002: CAMP -678.182 2.310

0 50 100 150 200

7/13/ 6 7/14/ 6 7/15/ 6 DateNOX [ppb] Minimum to Maximum Range Observed Predicted

80310002: CAMP -678.182 2.310

0 200 400 600 800 1000 1200 1400 1600 1800 2000

7/13/ 6 7/14/ 6 7/15/ 6

DateCO [ppb] Minimum to Maximum Range Observed Predicted

CAMP: 2105 Broadway -678.182 2.310

0 10 20 30 40 50 60 70 80 90 100 110 120

7/13/ 6 7/14/ 6 7/15/ 6

DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure 2-12b. Comparison of hourly NOx (top) and ozone (bottom) predicted and observed time series at the CAMP monitoring site for July 13-15, 2006 and the final CAMx Run17 2006

base case simulation base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-41 2.4.3 July 27-29, 2006



### The July 27-29, 2006 episode was the most seve re 3-day ozone episode that occurred during

2006. 8-hour ozone exceedances occurred on all thr ee days and there were a total of 10 monitordays of exceedances in the Denver area, includi ng 2 days at the key RFNO monitoring site.

Table 2-9 displays the 1-hour and 8-hour performa nce statistics for July 27-29, 2006 all of which achieve EPA’s performance goals, although with an underprediction bias of the 1-hour ozone

statistics.

Table 2-9. Final CAMx Run 17 2006 base case simulation daily 1-hour and 8-hour statistical performance measures for the July 27-29, 2006 episode and comparison with EPA performance goals.

2006 Performance
Statistic EPA
Goal July 27 July 28 July 29

1-Hour Ozone Unpaired Peak ≤ ±20% -11.8 7.8 -1.2

Normalized Bias ≤ ±15% -9.6 -9.7 -9.1

Normalized Error ≤ 35% 13.1 14.8 12.4

8-Hour Ozone Unpaired Peak ≤ ±20% -10.3 -6.2 -6.3

Normalized Bias ≤ ±15% 1.0 -1.8 3.2

Normalized Error ≤ 35% 13.6 12.3 14.2



### The comparison of the predicted and observed sp atial distributions of daily maximum 8-hour ozone concentrations on July 27 th 

### confirm the model unde rprediction bias on this day (Figure 2-13a). The model predicts elevated ozone ma inly to the north and northwest of downtown, whereas the peak observed values are south of Denver. Although the modeled 8-hour ozone peak (78 ppb) is in the direction of an observe d 82 ppb ozone peak in Weld County. Clearly the model is failing to capture what caused the obs erved high ozone south of Denver on this day.

Better ozone performance is seen on July 28 th 

### (Figure 2-13b). The model correctly locates the elevated ozone cloud northwest of Denver, althou gh ozone formation appears to be slower in then model than observed so the peak ozone occurs farther downwind. The model elevated ozone cloud also appears to be slight displaced westward only glancing the FTCW monitor where high ozone was recorded (87 ppb).

July 29, 2006 was the most adverse ozone da y during 2006 in the DMA. High ozone values

were recorded at numerous monitors with exc eedances even recorded at the Carriage monitor close to downtown. On other days we noted th e too slow ozone formation in the model that

caused the modeled ozone to occu r too far downwind and away from Denver, such is not the case on this day. The highest modeled ozone in excess of 85 ppb is estimated south of

downtown Denver where observed values of 83-97 ar e recorded. Elevated predicted ozone is estimates at RFNO (~80 ppb) where an exceedan ce is observed (97 ppb). And high modeled

values are estimated to stretch to the FCTW monitor (~75 ppb), where another ozone exceedance is observed (95 ppb).F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-42 Figure 2-13a. Spatial distribution of the predicted and observed daily maximum 8-hour ozone concentrations (ppb) in the Denver area on July 27, 2006 for the final CAMx Run 17 2006 base

case simulation



### .F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-43 Figure 2-13b. Spatial distribution of the predicted and observed daily maximum 8-hour ozone concentrations (ppb) in the Denver area on July 28, 2006 for the final CAMx Run 17 2006 base

case simulation



### .F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-44 Figure 2-13c. Spatial distribution of the predicted and observed daily maximum 8-hour ozone concentrations (ppb) in the Denver area on July 29, 2006 for the final CAMx Run 17 2006 base

case simulation



### .F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-45 Figure 2-14 displays the time series of predicte d and observed hourly ozon e concentrations at key sites for the July 27-29, 2006 episode. For si tes to the northeast of Denver (Figure 2-14a), the ozone model performance is quite good. The model follows the observed ozone variations at the NREL and ARVA well, although the hourly ozone peaks on July 29 th 

### are underestimated a little. The observed hourly ozone at RFNO is tr acked well on July 27-29, 2006, again the hourly ozone peak on July 29 th 

### is underpredicted slightly. Furthe r northeast from Denver at the SOBC, the ozone model performance is also quite good.

At the CARR site just west of downtown Denve r and WELC site to th e southwest of downtown Denver, ozone model performance is also good, albeit the peaks on July 29 th 

### are underestimated (Figure 2-14b). South of De nver at the CHAT and HIGH mon itoring sites the observed ozone on July 27 th 

### is underestimated, but model performance for July 28 and 29 is quite good.

At sites north of Denver (Figure 2-14c), ozone m odel performance is not as good as seen for the other sites with the daytime ozone peaks too low. As seen on some of the other days, the model reproduces the observed rate of ozone formation in the morning but then stalls out around noon

while the observed values continue to rise.

Figure 2-15 compares the predicted and observed hourly NOx, CO and ozone time series at the

CAMP and WELB sites in Denver. The model reproduces the observed NOx and CO concentrations reasonable well, but with an ove rprediction bias during the day at WELB. The ozone is also reproduced well at these two site s. The model fuels to reproduce the very high observed morning NOx spike on July 28 th 

### at both sites and overpredicts the CO spikes on July

29 th 

### at WELB but less so at CAMP, whether this is an emissions or mixing issue can not be

discerned.

.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-46 ARVA: Arvada -687.213 8.568

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### NREL: National Renewable E -694.376 2.926

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed PredictedF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-47 RFNO: Rocky Flats North -693.592 21.629

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### SOBC: South Boulder Creek -697.351 26.869

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure 2-14a. Time series of predicted and observed hourly ozone concentrations (ppb) for the July 27-29, 2006 period, monitoring sites to the Northwest of downtown Denver
and the final CAMx Run17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-48 WELC: Welch -692.154 -8.925

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### CARR: Carriage -681.834 2.717

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed PredictedF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-49 HIGH: Littleton -677.368 -18.104

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### CHAT: Chatfield -687.313 -20.937

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure 2-14b. Time series of predicted and observed hourly ozone concentrations (ppb) for the July 27-29, 2006 period, monitoring si tes mostly south of downtown Denver and
the final CAMx Run17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-50 WCTO: Weld County Tower -651.000 70.457

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### FTCO: Fort Collins South -677.801 94.012

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed PredictedF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-51 FTCW: Fort Collins West -682.854 96.141

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6



### DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure 2-14c. Time series of predicted and observed hourly ozone concentrations (ppb) for the July 27-29, 2006 period, monitoring sites to the North of downtown Denver and
the final CAMx Run17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-52 80310002: CAMP -678.182 2.310

0 50 100 150 200

7/27/ 6 7/28/ 6 7/29/ 6 DateNOX [ppb] Minimum to Maximum Range Observed Predicted

80310002: CAMP -678.182 2.310

0 200 400 600 800 1000 1200 1400 1600 1800 2000

7/27/ 6 7/28/ 6 7/29/ 6

DateCO [ppb] Minimum to Maximum Range Observed Predicted

CAMP: 2105 Broadway -678.182 2.310

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6

DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure 2-15a. Comparison of hourly NOx (top) and ozone (bottom) predicted and observed time series at the CAMP monitoring site for July 27-29, 2006 and the final CAMx Run17 2006

base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-53 80013001: Welby -674.141 11.613

0 50 100 150 200

7/27/ 6 7/28/ 6 7/29/ 6 DateNOX [ppb] Minimum to Maximum Range Observed Predicted

80013001: Welby -674.141 11.613

0 200 400 600 800 1000 1200 1400 1600 1800 2000

7/27/ 6 7/28/ 6 7/29/ 6

DateCO [ppb] Minimum to Maximum Range Observed Predicted

WELB: Welby -674.141 11.613

0 10 20 30 40 50 60 70 80 90 100 110 120

7/27/ 6 7/28/ 6 7/29/ 6

DateO3 [ppb] Minimum to Maximum Range Observed Predicted



### Figure 2-15b. Comparison of hourly NOx (top) and ozone (bottom) predicted and observed time series at the Welby monitoring site for July 27-29, 2006 and the final CAMx Run17 2006

base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec2_MPE_Ozone1.doc August 2008 

### 2-54 2.5 OZONE OPERATIONAL MODEL PERFORMANCE EVALUATION

CONCLUSIONS



### The ozone operational model performance ev aluation of the CAMx Run 17 2006 base case simulation of the June-July 2006 period has found some days when the model reproduces the observed ozone quite well, where as others where the model does not simulate the ozone well. A vast majority of the modeling days achieve EP A’s ozone model performance goals, lending some confidence that the model is performing well enough for use in making future year ozone projections. However, we should be taken that such ozone project ions are not relying solely on poorly performing model days.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-1 3.0 DIAGNOSTIC MODEL PERF ORMANCE EVALUATION

3.1 INTRODUCTION In the previous section we pe rformed an operational model perf ormance evaluation of the final

CAMx Run 17 2006 base case simulation that ad dressed how well the model reproduces the surface hourly and 8-hour ozone concentrations in the Denver Metropolitan Area (DMA) (i.e., does the model get the right answer). In this section we perform a diagnostic model performance evaluation that compares the model predictions against ozone precursor s, ozone aloft, key indicator species and tries to address the issue of whether the model is ge tting the right answer for the right reason. We also present in this se ction an evaluation of th e base case simulation for particulate matter (PM) species. However, because the focus of the Denver June-July 2006 modeling was on ozone, very little effort was de voted to developing the PM precursor emissions inventory and no effort was made to optimize the model configuration for PM performance.

3.2 OZONE PRECURSOR MODEL PERFORMANCE

The performance for ozone precursors is ex amine using the routin e hourly NOx and CO monitoring network in the DMA and using sp ecial study Volatile Organic Compound (VOC) grab sampling at several sites conducted by th e CDPHE/APCD that occu rred during portions of the June-July 2006 episode.

3.2.1 Routine Performance for Hourly NOx and CO Concentrations

Figure 3-1 displays the same daily model perfor mance statistics for hourly NOx concentrations

in the DMA as used for ozone. NOx is collect ed at two sites in the DMA (CAMP and WELB) and is a primary emitted pollutant. We would not expect the model to produce model performance for NOx anywhere near as good for ozone as NOx is highly influenced by subgridscale emissions variations that can not be cap tured by the model. Although the ozone model performance goals are provided in Figure 3-1, th ey are not expected to be achieved for NOx model performance. For example, the CAMP mon itor is located at the intersection of several major downtown streets that is affected by local mobile sources, whereas the model is predicting a 4 km by 4 km average concentration. Given th is, it is not surprising that the model usually underestimates the maximum hourly NOx concentra tions at the monitor (top panel in Figure 3- 1). Over all hours the model is exhibiting an ove rprediction bias in hourly NOx concentrations that is mainly due to an underprediction of th e daytime low NOx concentrations at Welby shown in the previous Chapter. Because the norma lized bias performance metric normalizes the difference in the predicted and observed hourly NOx concentrations by the observation, as the observed NOx concentration approaches zero it tends to blow up and become very large.

Figure 3-2 displays model performance statistics fo r hourly CO concentrati ons that are collected at 13 sites in the DMA. Again because CO is a primary emitted species that is emitted mainly by mobile sources, it can exhibit larg e spatially variations within shor t distances that is not captured by a photochemical grid model using a 4 km grid resolution. Even with these caveats, the model appears to estimate reasonable levels of CO concen trations that are similar to the observed values

on average.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-2 Denver Run 17 2006 Base Case Hourly NOx.

Unpaired Peak Accuracy

-100

-50

0 50 1006/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

+20%

-20%

Average Paired Peak Accuracy

-100

-50

0 50 1006/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

Normalized Bias

-50

0 50 100 150 2006/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

+15%

-15%

Normalized Error

0 50 100 150 200 250 3006/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

35% Peak Observed and Paired Predicted

0 50 100 150 200 2506/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(ppb) Observed

Run17



### Figure 3-1a. Daily model performance statistics for June 2006, hourly NOx concentrations in the DMA (CAMP and WELB) and the final CAMX Run 17 2006 base

case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-3 Denver Run 17 2006 Base Case Hourly NOx.

Unpaired Peak Accuracy

-100

-50

0 50 1007/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

+20%

-20%

Average Paired Peak Accuracy

-100

-50

0 50 1007/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

Normalized Bias

-50

0 50 100 150 2007/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

+15%

-15%

Normalized Error

0 50 100 150 200 250 3007/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

35% Peak Observed and Paired Predicted

0 50 100 150 200 2507/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(ppb) Observed

Run17



### Figure 3-1b. Daily model performance statistics for July 2006, hourly NOx concentrations in the DMA (CAMP and WELB) and the final CAMX Run 17 2006 base

case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-4 Denver Run 17 2006 Base Case Hourly CO.

Unpaired Peak Accuracy

-60 -40 -20

0 20 40 606/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

+20%

-20%

Average Paired Peak Accuracy

-50

0 50 1006/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

Normalized Bias

-40 -20

0 20 40 60 80 1006/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

+15%

-15%

Normalized Error

0 20 40 60 80 1006/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(%) Run17

35% Peak Observed and Paired Predicted

0 500 1000 1500 2000 25006/16/26/36/46/56/66/76/86/96/106/116/126/136/146/156/166/176/186/196/206/216/226/236/246/256/266/276/286/296/30(ppb) Observed

Run17



### Figure 3-2a. Daily model performance statistics for June 2006, hourly CO concentrations in the DMA (13 sites) and the final CAMX Run 17 2006 base case

simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-5 Denver Run 17 2006 Base Case Hourly CO.

Unpaired Peak Accuracy

-100

-50

0 50 1007/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

+20%

-20%

Average Paired Peak Accuracy

-50

0 50 1007/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

Normalized Bias

-50

0 50 100 1507/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

+15%

-15%

Normalized Error

0 50 100 1507/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(%) Run17

35% Peak Observed and Paired Predicted

0 500 1000 1500 2000 2500 30007/17/27/37/47/57/67/77/87/97/107/117/127/137/147/157/167/177/187/197/207/217/227/237/247/257/267/277/287/297/30(ppb) Observed

Run17



### Figure 3-2b. Daily model performance statistics for July 2006, hourly CO concentrations in the DMA (13 sites) and the final CAMX Run 17 2006 base case

simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-6 3.2.2 VOC and Key Indicator Model Performance

During the summer of 2006, the CDPHE/APCD colle cted 3-hour grab canister samples at several sites in the DMA as shown in Figure 3-3 and Ta ble 3-1. Morning VOC samples were collected at the CAMP and Welby sites in the metropolitan Denver as well as Fort Lupton and Platteville up in Weld County. Afternoon VOC samples were collected at the Rocky Flats North and Fort Collins West high ozone (downwind) monitors. The VOC samples at the two Denver sites (CAMP and WELB) will provide an evaluation of the model’s on-ro ad mobile source emissions inventory, whereas the morning samples at the tw o Weld County sites will provide an evaluation of the oil and gas VOC emissions inventory that dominates the VOC inventory in Weld County.

Figure 3-3. Locations of monitoring sites where VOC samples were collected during the
summer of 2006.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-7 Table 3-1a. Locations of monitoring sites where VOC samples were collected during the
summer of 2006. 2006 Ozone Precursor Monitoring Sites

AQS # Site Name Address Latitude Longitude Elevation

08-001-3001 Welby 3174 E. 78th Ave., Denver, 80229 39 50 21 104 56 56 1550 m

08-031-0002 CAMP 2105 Broadway, Denver,

80205 39 45 04 104 59 14 1591 m

08-123-0008 Platteville 1004 Main St., Platteville,

80651 40 12 40 104 49 25 1476 m

08-123-0011 Fort Lupton Kahil St. & Fulton Ave., Fort Lupton, 80621 40 04 28 104 48 53 1498 m

08-059-0006 Rocky Flats - N 16600 W. Highway 128, Broomfield, 80021 39 54 46 105 11 18 1796 m

08-069-0011 Fort Collins - West 3416 W. LaPorte Ave., Fort Collins, 80525 40 35 32 105 08 27 1575 m



### Table 3-1b. Sampling schedule and times for summer of 2006 VOC sampling study in the

DMA.

2006 Ozone Precursor Monitoring Sites

AQS # Site Name Sample Period Time Period 08-001-3001 Welby 16 June – 31 July 2006, every 3 rd day A.M. --- 06:00 – 09:00 (MDT)
08-031-0002 CAMP 16 June – 31 July 2006, every 3 rd day A.M. --- 06:00 – 09:00 (MDT)

08-123-0008 Platteville 16 June – 31 July 2006, every 3 rd day A.M. --- 06:00 – 09:00 (MDT)

08-123-0011 Fort Lupton 16 June – 31 July 2006, every 3 rd day A.M. --- 06:00 – 09:00 (MDT)
08-059-0006 Rocky Flats - N 28 June – 13 July 2006, on-call basis P.M. --- 13:00 – 16:00 (MDT)
08-069-0011 Fort Collins - West 19 July – 28 July 2006, on-call basis P.M. --- 13:00 – 16:00 (MDT)



### These VOC canister samples were speciated to ob tain individual VOC species concentrations along with total nonmethane hydrocarbon (TNMHC) c oncentrations that were compared against

the model results to determine how well the model predicted total VOC concentrations,

concentrations of individual VOC species as well as predic ting the key VOC/NOx indicator species ratios. However, before the measured VOC concentrations could be compared against the modeled values the following ac tivities had to be performed:

• Time shift of the measured data to the MST time zone being used in the modeling;

• Adjustment of the VOC species to account for concentrations below the minimum detection level (MDL) whereby a fairly st andard practice of setting VOC species

concentrations that are below di ction to half of the MDL; and

• Speciated the VOC speciation samples to the CB05 VOC species used in the modeling.

The speciation of the VOC samples into the CB 05 species was performe d by the research group at Colorado University under th e direction of Dr. Jana Milford whose assistance was greatly appreciated.

The conversions of the measured VOC species c oncentrations to the CB05 species was necessary in order to obtain an “apples-to-apples” comp arison of VOC species and total VOC between the model predictions and observati ons. The raw VOC measurements can not be directly compared

with the modeled VOC concentrations. There are portions of several VOC species that areF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-8 considered nonreactive (NR) in the CB05 VOC classification system so are dropped in the model VOC species. In addition, the VOC sampling di d not speciate their samples for methanol (MeOH) and ethanol (EtOH) that are two species in the CB05 chemical mechanism so those two species were dropped from the comp arison. In addition, ethane (ETHA) is an explicit species in CB05 but is considered nonreactive by EPA’s reac tivity classification scheme so is not included

in the definition of “total VOC” used in this evaluation. However, the model performance for ethane is evaluated separately. Thus, the total VOC comparisons presented below will not include all VOC compounds, but they will include consistent compounds between the observations and model predictions so are an ap propriate comparison from a model performance evaluation perspective. However, when looking at the VOC/NOx ratios a nd trying to interpret

results in terms of whether ozone formation is more VOC-limited or NOx-limited the user should be aware that not all VOC compounds are present in the “total VOC” concen trations used in the model performance evaluation.

3.2.2.1 VOC Performance in Denver Urban Area

VOC samples were collected at the CAMP and We lby monitoring sites that are located within the heart of the DMA. VOC, NOx and CO con centrations at these tw o urban sites will be dominated by on-road mobile sources. Conseque ntly, the model performance at these two sites will help assess the accuracy of the on-road mobile source emissions inventory. As noted above,

there are a lot of local- a nd microscale effects (e. g., streets) that result in high spatial variability in the observed VOC, NOx and CO concentrations that can not be captured by the model predictions that are averaged acr oss a 4 km by 4 km grid cell with a layer 1 top of approximately 36 m AGL. Thus, in evaluating model performan ce for ozone precursors at these sites, more emphasis is placed on the performance for VOC /NOx and CO/NOx ratios then for VOC, NOx and CO concentrations. Since VOC, NOx and CO are all dominated by on-road mobile sources at these two sites, the subgrid-scal e effects on the three pollutants s hould be very similar. Given

that there is more confidence in the on-road mobile source NOx emissions than the VOC and CO emissions, then an evaluation of the model at these sites for VOC/NOx and CO/NOx ratios provides a good indication of the accuracy of the on-road mobile source VOC and CO emissions. The performance for VOC/NOx ratios will also pr ovide an indication of whether the model is predicting the correct chemical regimes and will predict oz one responses to changes in VOC and NOx emissions in the correct fashion (i.e., gett ing the right answer for the right reason).

Figure 3-4a compares the predicted and obser ved morning 3-hour av erage VOC, NOx and CO concentrations at the CAMP monitor. Although there are a few outliers, in general the observed VOC concentrations are approximately 200 ppbC th at is approximately a factor of two higher than the modeled values (~100 ppbC). Simila rly, the observed NOx concentrations are approximately 100 ppb that are approximately a f actor of 2 higher than predicted (~50 ppb). With one exception, the observed VOC and NOx con centrations are always the same or higher than the predicted values. The exception is on July 4, 2006 when the observed value is 10 ppb

that is twice as low is the next lowest NOx obs ervation and an order of magnitude lower than the average observed NOx concentrations at this site. July 4 has very unusual and atypical traffic patterns and it is not surprising that it is an outlie r compared to the other days. On-road mobile source emissions representative of a Sunday were used for July 4, but that likely did not fully capture the unusual and atypical tra ffic patterns for this holiday day.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-9 Of the 15 days with morning samples at the CAMP monitor, there is excellent agreement with the predicted and observed VOC/NOx ratios for 11 of the 15 days (73% of the days; Figure 3-4b, top). On the four days when there is not exce llent agreement with the predicted and observed

VOC/NOx ratios at the CAMP mo nitor, one is the July 4 th 

### outlier day discussed previously. On July 22, 2006 (a Saturday) the model predicts a 2.5 VOC/NOx ratio when an 8.3 ratio was observed. Whereas on June 25 (a Sunday) and July 22 (a Thursday) VOC/NOx ratios of 5.9 and

5.1 were observed with modeled va lues of 3.8 and 3.2, respectively.

The model is generally overpredicting the observed morning CO/NOx ratio at the CAMP monitor (Figure 3-4b, middle). With a few excepti ons, this overprediction is not large, but is systematic and may indicate an overrestimation of th e on-road mobile source CO emissions.

With the exception of July 19, 2006, observed morn ing ethane (ETHA) concentrations at the CAMP monitoring are underpredi cted by a large amount at the CAMP monitor with average observed values near 25 ppbC and average mode led values an order magnitude lower (~2.5 ppbC). This is undoubtedly partly due to EPA’ s classification of etha ne as a nonreactive VOC species so it is not included in a standard VOC emissions inventory. Although ethane was

included in the WRAP Phase III oil and gas emissions inventory for the Denver-Julesburg Basin, it is likely missing for some sources in the DMA so it is not surprising that it is underestimated by the model. Since ethane has very low reac tivity this should not adversely affect ozone formation, model performance or response to cont rols, but it certainly affects ethane model performance.

The comparison of VOC, NOx and CO concentra tions and VOC/NOx and CO/NOx ratios at the Welby monitor are shown in Figure 3-5. As noted in Chapter 2, there appear to be more issues with subgrid-scale variability at the Welby monitor then at CAMP. There is also more missing data at Welby so there are less VOC/NOx and CO /NOx ratio comparisons. Results at Welby are

similar to CAMP with the model underestima ting VOC and NOx concentr ations, but generally predicting the same magnit ude of CO concentrations as obse rved (Figure 3-5a). Although there is good agreement with the modeled and observe d VOC/NOx ratios on some days (June 19 and July 7, 10 and 16) the model unde rpredicts the observed VOC/NOx ratio on June 16 and 22 and July 1 and 4.

Table 3-2 summarizes the predicted and observe d morning VOC/NOx ratio comparisons at the CAMP monitoring site in downtown Denver that al so includes the day of week. As noted above, for most days these comparisons are very good, which is likely due to the extra effort invested in the Denver modeling of on-road mobile sources us ing the CONCEPT emissions model. Both the observed and predicted VOC/NOx ratios are higher on the weekend days, with Sunday being higher than Saturday, and lower on weekdays . The model underestimates the observed VOC/NOx ratio on Sunday June 25 by -25%, but agrees quite well on Sunday July 16. Similar results are seen for the two Saturday comparis ons with good agreement on July 1 (+13%) and an underprediction bias on July 22 (-38%). Thus, the model appears to be capturing much of the weekend effect on mobile sources, but may not be capturing the full effect on all days. However, with just four days of weekend comparisons it is hard to draw firm conclusions.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-10 Table 3-2. Comparison of predicted and observed morning CB05-VOC/NOx ratios at the downtown Denver CAMP monitoring site.

VOC/NOx Ratios

Date Day of
Week Observed Predicted Percent
Difference

June 16 Fri 3.31 2.56 -22%

June 19 Mon 1.58 2.18 +38%

June 22 Thurs 8.30 2.52 -70%
June 25 Sun 5.85 3.81 -35%

June 28 Wed 2.27 2.01 +13%

July 1 Sat 3.04 3.42 +13% July 4 Holiday 17.74 2.18 -88% July 7 Fri 2.57 2.21 +36% July 10 Mon 2.07 2.82 +36% July 13 Thurs 2.42 2.39 -1% July 16 Sun 3.68 3.81 +3% July 19 Wed 1.64 2.39 +46% July 22 Sat 5.13 3.17 -38% July 25 Tue 2.60 2.20 -15% July 28 Fri 2.00 2.50 +25%F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-11 

### Predicted vs. Observed VOC at CAMP

0.00 100.00 200.00 300.00 400.00606166061960622606256062860701607046070760710607136071660719607226072560728

DateVOC [ppbC] Predicted Observed



### Predicted vs. Observed NOx at CAMP

0 50 100 150 200606166061960622606256062860701607046070760710607136071660719607226072560728

DateNOx [ppb] Predicted Observed



### Predicted vs. Observed CO at CAMP

0 200 400 600 800 1000 1200606166061960622606256062860701607046070760710607136071660719607226072560728

DateCO [ppb] Predicted Observed



### Figure 3-4a. Comparison of predicted and observed 3-hour average morning (5-8am MST) CB05-VOC, NOx and CO concentrations at the CAMP monitor for the CAMx Run

17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-12 

### Predicted vs. Observed VOC/NOx Ratio at CAMP

0 2 4 6 8 10606166061960622606256062860701607046070760710607136071660719607226072560728

DateVOC/NOx[ppbC/ppb] Predicted Observed



### Predicted vs. Observed CO/NOx Ratio at CAMP

0 5 10 15 20 25 30606166061960622606256062860701607046070760710607136071660719607226072560728

DateCO/NOx [ppb/ppb] Predicted Observed



### Predicted vs. Observed ETHA at CAMP

0 10 20 30 40 50 60606166061960622606256062860701607046070760710607136071660719607226072560728

DateETHA [ppbC] Predicted Observed



### Figure 3-4b. Comparison of predicted and observed 3-hour average morning (5-8am MST) CB05-VOC/NOx and CO/NOx ratio and ethane (ETHA) concentrations at the
CAMP monitor for the CAMx Run 17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-13 Predicted vs. Observed VOC at Welby

0.00 100.00 200.00 300.00606166061960622606256062860701607046070760710607136071660719607226072560728

DateVOC [ppbC] Predicted Observed



### Predicted vs. Observed CO at Welby

0 200 400 600 800 1000606166061960622606256062860701607046070760710607136071660719607226072560728

DateCO [ppb] Predicted Observed 

### Predicted vs. Observed NOx at Welby

0 50 100 150606166061960622606256062860701607046070760710607136071660719607226072560728

DateNOx [ppb] Predicted Observed



### Figure 3-5a. Comparison of predicted and observed 3-hour average morning (5-8am MST) CB05-VOC, NOx and CO concentrations at the WELB monitor for the CAMx Run

17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-14 Predicted vs. Observed VOC/NOx Ratio at Welby

0 2 4 6 8 10606166061960622606256062860701607046070760710607136071660719607226072560728

DateVOC/NOx[ppbC/ppb] Predicted Observed



### Predicted vs. Observed CO/NOx Ratio at Welby

0 10 20 30 40 50606166061960622606256062860701607046070760710607136071660719607226072560728

DateCO/NOx [ppb/ppb] Predicted Observed



### Predicted vs. Observed ETHA at Welby

0 10 20 30 40 50 60606166061960622606256062860701607046070760710607136071660719607226072560728

DateETHA [ppbC] Predicted Observed



### Figure 3-5b. Comparison of predicted and observed 3-hour average morning (5-8am MST) CB05-VOC/NOx and CO/NOx ratio and ethane (ETHA) concentrations at the Welby monitor for the CAMx Run 17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-15 3.2.2.2 VOC Comparisons in Weld County

Unlike the two Denver VOC sampling sites, NOx a nd CO were not collected at the two Weld County sites so we can only make model-obs erved comparisons for total CB05-VOC and Ethane, which are shown in Figure 3-6. At Ft . Lupton the modeled VOC ranges from 40 to 226 ppbC, whereas the observed values range from 1 22 to 981 ppbC. Most modeled VOC values at Ft. Lupton are between 100-200 ppbC, whereas mo st observed values range from 250 to 700 ppbC. Similar results are seen at Plattevill e where the modeled VOC ranges from 50 to 200 ppbC, whereas the observed values range from 200 to 2,000 ppbC.

The model is also underpredicti ng the observed ethane concentra tions at the two Weld County sites (Figure 3-7). At Ft. L upton the observed ethane values range from 24 to 240 ppbC, with average values of around 150 ppbC. Whereas the m odel ethane predictions range from 6 to 43 ppb, with average values of approximately 25 ppbC that are over a 100 ppbC lower than observed on average. Even larger ethane underp rediction bias is seen at Platteville with observed values of 35 to 600 ppbC and modeled values of 9 to 80 ppbC.

The model systematic underprediction of ethane in Denver and Weld County suggest that there are missing sources of natu ral gas in the inventory.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-16 

## Predicted vs. Observed VOC at Ft Lupton

0.00 200.00 400.00 600.00 800.00 1000.00 1200.00606166061960622606256062860701607046070760710607136071660719607226072560728



### DateVOC [ppbC] 

### Predicted Observed



## Predicted vs. Observed VOC at Platteville

0.00 500.00 1000.00 1500.00 2000.00 2500.00606166061960622606256062860701607046070760710607136071660719607226072560728



### DateVOC [ppbC] 

### Predicted Observed

Figure 3-6. Comparison of the predicted and observed morning CB05-VOC concentrations at the Ft. Lupton and Platteville sites in Weld County.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-17 

## Predicted vs. Observed ETHA at Ft Lupton

0 50 100 150 200 250 300606166061960622606256062860701607046070760710607136071660719607226072560728



### DateETHA [ppbC] 

### Predicted Observed



## Predicted vs. Observed ETHA at Platteville

0 100 200 300 400 500 600 700606166061960622606256062860701607046070760710607136071660719607226072560728



### DateETHA [ppbC] 

### Predicted Observed

Figure 3-7. Comparison of the predicted and observed morning CB05-VOC concentrations at the Ft. Lupton and Platteville sites in Weld County.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-18 3.2.3 Speciated VOC Comparisons

Figure 3-8 compares the speciat ed CB05 VOC concentrations for three days at the CAMP monitor. There is similarity in the speciat ed VOC model performance so just 3 days are reproduced. Paraffin (PAR) are reproduced we ll on June 19, but underestimated by 30-40 ppbC on July 13 and 28. Olefins (OLE) are underestimated by approximately a factor of two. The two aromatic species (TOL and XYL) are overestimated on June 19 but underestimated on the two July days. Formaldehyde (FORM) is underpredicted by approximately a factor of 2 on all three days. Acetaldehyde (ALD2) is greatly underestim ated by the model with observed values of ~9 ppbC and modeled values a factor of ~6 lower at ~1.5 ppbC. Higher aldehydes are

overestimated on June 19 and underestimated on the other two days. Ethene (ETH) is underestimated by 20-40%. ISOP and TERP, that are mainly biogenic VOC species, are almost

nonexistent in the observed and mode led VOC concentrations at CAMP.

CB05 VOC species performance results at the Wel by monitor (Figure 3-9) are similar to what was seen at CAMP. PAR is reproduced reas onable well on June 19, but underpredicted by 90 ppb on July 13 (samples for July 28 were missing) . Formaldehyde is again underestimated by a factor of two, and acetaldehyde is underestimated by approximately a factor of 6. Ethane is underpredicted by a factor of 3 on J une 19 and a factor of 20 on July 13.

The ETHA and PAR underestimation bias sugge sts missing natural gas emissions in the emissions inventory. This issue is discussed in more detail below when looking at the Weld County monitors. The underpredi ction of FORM is of concern since it is an important VOC species that initiates the radical cycle.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-19 Predicted and Observed CB05 Species at CAMP on June 19, 2006 (5-8AM MST)

0 20 40 60 80 100 120PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204



### Predicted and Observed CB05 Species at CAMP on June 19, 2006 (5-8AM MST)

0 2 4 6 8 10PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204



### Figure 3-8a. Comparison of predicted and observed 5-8am MST CB05 VOC species at the CAMP monitor on June 19, 2006.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-20 Predicted and Observed CB05 Species at CAMP on July 13, 2006 (5-8AM MST)

0 20 40 60 80 100 120PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204



### Predicted and Observed CB05 Species at CAMP on July 13, 2006 (5-8AM MST)

0 2 4 6 8 10PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204



### Figure 3-8b. Comparison of predicted and observed 5-8am MST CB05 VOC species at the CAMP monitor on July 13, 2006.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-21 Predicted and Observed CB05 Species at CAMP on July 28, 2006 (5-8AM MST)

0 20 40 60 80 100 120PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204



### Predicted and Observed CB05 Species at CAMP on July 28, 2006 (5-8AM MST)

0 2 4 6 8 10PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204



### Figure 3-8c. Comparison of predicted and observed 5-8am MST CB05 VOC species at the CAMP monitor on July 28, 2006.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-22 Predicted and Observed CB05 Species at Welby on June 19, 2006 (5-8AM MST)

0 50 100 150PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204



### Predicted and Observed CB05 Species at Welby on June 19, 2006 (5-8AM MST)

0 2 4 6 8 10PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204



### Figure 3-9a. Comparison of predicted and observed 5-8am MST CB05 VOC species at the Welby monitor on June 19, 2006.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-23 Predicted and Observed CB0 5 Species at Welby on July 13, 2006 (5-8AM MST)

0 50 100 150PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204



### Predicted and Observed CB0 5 Species at Welby on July 13, 2006 (5-8AM MST)

0 2 4 6 8 10PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204



### Figure 3-9b. Comparison of predicted and observed 5-8am MST CB05 VOC species at the Welby monitor on July 13, 2006.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-24 VOC species at the two Weld County monitors are dominated by ethane (ETHA) and paraffin (PAR). Table 3-3 compares the predicted and observed PAR and ETHA concentrations at Ft. Lupton and Platteville and Figur e 3-10 compares the other CB05 VOC species at Ft. Lupton and three days. The large underpredi ction of PAR and ETHA at these sites (typically -70% to -80%) indicate missing natural gas emissions in th e inventory (Table 3-3). In addition to underestimating FORM and ALD2, as seen at th e two Denver monitoring sites, the aromatic species are also underestimates at the Weld County sites, which suggest that gasoline combustion VOC emissions may be underestimated in the inventory as well.

Table 3-3. Comparison of predicted and observed morning paraffin (PAR) and ethane (ETHA) concentrations at the Weld County monitoring sites.

Site Date Observed Predicted Difference Difference (ppbC) (ppbC) (ppbC) (%)

PAR Ft. Lupton June 19 403 119 284 -70% Ft. Lupton July 13 321 67 254 -79% Ft. Lupton July 28 455 105 350 -77%

Platteville June 19 484 224 260 -54% Platteville July 28 779 267 512 -66%

ETHA Ft. Lupton June 19 88 18 70 -80% Ft. Lupton July 13 41 9 32 -77% Ft. Lupton July 28 96 13 83 -77%

Platteville June 19 97 31 66 -68% Platteville July 28 161 34 127 -79%F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-25 Predicted and Observed CB05 Species at Ft Lupton on June 19, 2006 (5-8AM MST)

0 1 2 3 4 5PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204

Predicted and Observed CB05 Species at Ft. Lupton on July 13, 2006 (5-8AM MST)

0 1 2 3 4 5PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204

Predicted and Observed CB05 Species at Ft. Lupton on July 28, 2006 (5-8AM MST)

0 1 2 3 4 5PAROLETOLXYLFORMALD2ETHISOPETHAIOLEALDXTERPConcentration [ppb] Observed Run17.1204



### Figure 3-10. Comparison of predicted and observed CB05 VOC species at the Ft. Lupton monitoring site.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-26 3.3 OZONE MODEL PERFORMANCE ALOFT

NOAA collected ozonesonde measurements launc hed at Boulder that overlapped with our modeling period for six days. An ozonesonde collect s a vertical profile of ozone concentrations starting at the launch point (B oulder) and rising at a given rate that moves horizontally downwind by the prevailing winds. When matching the modeled vertical ozone profile with the ozonesonde data, we used the predicted ozone co ncentrations within th e grid cell above the launch point of the ozonesonde. Thus, we did not match up the horizontal location or time of the ozonesonde with the modeling results. Although the ozonesonde measurements went up to 20- 30 km, we only present the results for the lowest 10 km of the atmosphere as that is what is important for tropospheric ozone modeling.

One element of the Conceptual Model of high ozon e events in the Denver areas is that on some days there may be a reservoir of ozone aloft that is entrained into the mixed layer as it rises during the day. Thus, it will be interesting to see whether elevated ozone exists aloft that could be entrained into the mixed layer.

Figure 3-11 compares the predicted and observed ve rtical ozone profiles at Boulder for the six days that ozonesonde measurements were avai lable during the June-J uly 2006 modeling period. One general observation is that the model exhibi ts much less vertical variations in ozone concentrations than observed. This may be due in part by the fact that the model is just looking

at vertical variations in oz one over the launch point, wherea s the ozonesonde is measuring vertical, horizontal and tem poral changes in ozone as the ozonesonde moves downwind.

On June 15 th 

### there is good agreement between the pred icted and observed ozone in the lowest 2 km of the atmosphere (75-80 ppb). Between 2 km and 3 km AGL the observed ozone drops from 80 to 50 ppb, whereas the modeled values stay constant at 75-80 ppb. At ~5 km AGL the observed ozone rises from 50 to 90 ppb between 5 km and 6 km AGL and again matches the modeled value at 75-80 ppb between 6 km and 7 km . At 7 km the observed ozone rises to 250 ppb at 10 km AGL. This elevated ozone aloft is too high to be entrained in the mixing layer and is likely due to stratospheric ozone intrusion that is decoupled from the tropospheric ozone.

A comparison of the predicted and observed vert ical ozone profiles for the morning of June 23 are given in Figure 3-11b. The model and obs ervations agree on the reservoir of 75-80 ppb ozone above the morning inversion in the 1-2 km AGL height. However, above 2 km the observed values drop to a minimum of ~40 ppb at approximately 4 km AGL, whereas the modeled vertical ozone profile is constant at 75-80 ppb.

On June 29 th 

### the model estimates a nearly constant 65- 75 ppb variation in oz one in the vertical from the surface to 10 km AGL (Figure 3-11c). Th e observed vertical profile is also relatively

constant but has more variations from 55 ppb at the surface to 90 ppb at 10 km AGL.

On July 14, 2006 the model is predicting a constant ~70 ppb vertical ozone profile in the lowest 3 km of the atmosphere, whereas the observed values are 10-15 ppb higher (Figure 3-11d). Similarly, on July 21 the model (~55 ppb) is approximately 20 ppb lower than observed (~75 ppb) in the lowest 1 km of the atmosphere. Between 2 and 4 km AGL there is good agreement

between the modeled and observed vertical profile with a steady increase of from 55 ppb to 70 ppb (model) and 80 ppb (observed). However, above ~4 km AGL the model exhibits increasingF:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-27 ozone with height, but the obser ved ozone drops ~50 ppb with the observed value at 10 km AGL (55 ppb) being about 30 ppb lower than the model (85 ppb).

On July 26 the modeled ozone is below the observed ozone throughout the vertical profile (Figure 3-11f). The modeled ozone ranges from ~55 ppb at the surface and increases to ~65 ppb at 10 km AGL, whereas the observed values rang e form about 60 ppb at the surface increasing to over 100 ppb at 5 km AGL and then down to 75 ppb at 10 km AGL.

Maximum afternoon mixing heights in the Denver area would be expected to be in the 2,000 to 5,000 m AGL range. There does not a ppear to be any evidence of a reservoir of elevated ozone

aloft in the June ozonesonde measurements. Ho wever, the July ozonesonde measurements show elevated ozone aloft that is not captured by the model. Although these re sults are inconclusive, one potential explanation contributing to the unde rprediction of surface ozone concentrations at the high monitoring sites is the failure of the mo del to simulate the high ozone aloft that is entrained down to the surface as the mixing height rises.

Predicted and Observed Ozonesonde over Boulder on June 15, 2006 at 12pm

0 1 2 3 4 5 6 7 8 9 10

0 50 100 150 200 250 300

Ozone [ppb]Height above Surface [km] Observed Predicted, Run17.1204



### Figure 3-11a. Comparison of predicted and observed vertical distribution of ozone concentrations on June 15, 2006 for the CAMx Run 17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-28 Predicted and Observed Ozonesonde over Boulder on June 23, 2006 at 9am MST

0 1 2 3 4 5 6 7 8 9 10

0 20 40 60 80 100 120 140

Ozone [ppb]Height above Surface [km] Observed Predicted Run17.1204



### Figure 3-11b. Comparison of predicted and observed vertical distribution of ozone concentrations on June 23, 2006 for the CAMx Run 17 2006 base case simulation. 

### Predicted and Observed Ozonesonde over Boulder on June 29, 2006 at 9am MST

0 1 2 3 4 5 6 7 8 9 10

0 50 100 150 200

Ozone [ppb]Height above Surface [km] Observed Predicted Run17.1204



### Figure 3-11c. Comparison of predicted and observed vertical distribution of ozone concentrations on June 29, 2006 for the CAMx Run 17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-29 Predicted and Observed Ozonesonde over Boulder on July 14, 2006 at 11am MST

0 1 2 3 4 5 6 7 8 9 10

0 20 40 60 80 100 120

Ozone [ppb]Height above Surface [km] Observed Predicted Run17.1204



### Figure 3-11d. Comparison of predicted and observed vertical distribution of ozone concentrations on July 14, 2006 for the CAMx Run 17 2006 base case simulation. 

### Predicted and Observed Ozonesonde over Boulder on July 21, 2006 at 11am MST

0 1 2 3 4 5 6 7 8 9 10

0 20 40 60 80 100

Ozone [ppb]Height above Surface [km] Observed Predicted Run17.1204



### Figure 3-11e. Comparison of predicted and observed vertical distribution of ozone concentrations on July 21, 2006 for the CAMx Run 17 2006 base case simulation.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-30 Predicted and Observed Ozonesonde over Boulder on July 26, 2006 at 9am MST

0 1 2 3 4 5 6 7 8 9 10

0 20 40 60 80 100 120

Ozone [ppb]Height above Surface [km] Observed Predicted Run17.1204



### Figure 3-11f. Comparison of predicted and observed vertical distribution of ozone concentrations on July 26, 2006 for the CAMx Run 17 2006 base case simulation.



### 3.4 PM MODEL PERFORMANCE EVALUATION

In this section we compare the CAMx R un 17 2006 base case mode ling results against particulate matter (PM) species and PM related species concentr ations. However, the Denver June-July 2006 modeling database was set up for ozone modeling, not PM modeling. In fact, the CDPHE/APCD only provided 2006 base case emissions in Colorado for ozone precursor species (i.e., VOC, NOx and CO) and PM10 emissions for some categories . Thus, some of the PM emissions and PM related species are missing in Colorado. Where PM emissions data was available it was included, but give n the time constraints of th e study and the focus on ozone, no attempt was made to spend the extra resources and time to fill in th e missing PM precursor

emissions in Colorado.

Outside of Colorado the projected WRAP emi ssions inventory was used that includes PM precursors. However, these data were replaced with the CDPHE ozone precursor inventory in Colorado. For on-road mobile sources, the MO BILE6 emission factor model includes PM species with the SMOKE and CONCEPT emi ssions modeling so on-road mobile source emissions include PM precursors. For large stationary point s ources we used CEM data that

includes NOx and SO2 emissions. The MEGAN bi ogenic emissions model also includes PM precursor emissions. So the main source of miss ing PM emissions in Colorado is within the nonroad mobile and area source categories. Given th is, we would expect the model to underestimate PM concentrations. In particular, because most of the ammonia emissions are in the area source category, we would expect particulate ni trate (NO3) and ammonium (NH4) to be

underestimated.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-31 Total PM 2.5 

### mass measurements were collected at FRM and IMPROVE monitoring networks within the 12 km modeling domain. Figure 3- 12 displays the predicte d and observed scatter plots of 24-hour average PM 2.5 

### mass concentrations for the two networks and the June-July 2006 modeling period. Not surprising, given the missi ng PM precursor emissions in Colorado for some source categories, there is an underp rediction tendency for total PM2.5 mass with

fractional bias values of -90% to -100%.

Better performance is seen for SO4 concentra tions, albeit with an underestimation tendency (Figure 3-13). The fractional bias for SO4 across the CASTNET, IMPROVE and STN networks in the 12 km domain are -74%, -58% and -64%, respectively. A lthough this underprediction bias is due in part to missing SO2 and SO4 emissions, it is also affected by too much wet deposition of SO4 as evident by the overpredi ction of wet deposited SO4 at the NADP sites. Note that the

MM5 overstatement of the summer time convectiv e rainfall in the Four Corners states is a

common occurrence and much of the WRAP MM5 modeling effort was devoted to limiting the

overstated summer rainfall. For the Denver MM 5 modeling of the June-July 2006 period, we did

not observe overstated convective rainfall in the Denver area. However, that does not mean

MM5 did not overstate rainfall in other areas of the western U.S. that is likely causing the overstated of wet SO4 deposition ac ross the NADP monitoring sites.

Particulate nitrate (NO3) is greatly underestimat ed by the model (Figure 3-14). A large part of this underprediction is due to missing ammonia emissions in Colorado; NO3 particles can not form unless there is a buffering species and amm onia is the most common buffering agent in the western U.S. Without ammonia, all of the oxidize d NOx will stay as nitric acid (HNO3). In the top right panel of Figure 3-14 the modeled tota l nitrate (NO3+HNO3) is compared against the

CASTNet measured total nitrate a nd a much better comparison is s een. Although there still is an underprediction bias in total nitrat e, it is much lower than for NO3 and comparable to the other species.

Figure 3-15 displays the model performance for organic carbon (OC) and elemental carbon (EC) across the IMPROVE and STN monitoring networks. Note that the OC and EC measurements are more uncertain than the other PM species. Also note that although the monitors measure OC, the model predicts organic carbon matter (OCM) that includes other elements besides carbon.

For the OC model evaluation the observed OC was multiplied by 1.4 for comparison with the modeled OC in Figure 3-15.

As expected, both EC and OC are underestimated due to missing emissions, with the underestimation comparable to the other species. The exception is EC at the STN network that exhibits fairly reasonable fractional bias (-29%). This is likely because the EC emissions were

included in the on-road mobile source emissions and the urban-oriented STN sites are likely dominated by on-road mobile sources.

Because of the deficient PM precursor inventor y, the PM evaluation is inconclusive. As expected the model is underpredicting, and the u nderprediction appears to be consistent across the PM species. Given this, we elected not to expend any effort evaluating the model using the NPS ROMANS study database un til better PM precursor em issions can be developed.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-32 Figure 3-12. Comparison of predicted and observed total PM 2.5 

### mass model performance at FRM (left) and IMPROVE (right) sites in the 12 km modeling domain.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-33 Figure 3-13. Comparison of predicted and observed total sulfate (SO4) model performance at CASTNET (top left), IMPROVE (top right), STN (bottom left) and NADP (bottom right) monitoring sites in the 12 km modeling domain.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-34 Figure 3-14. Comparison of predicted and observed total nitrate (NO3) model performance at CASTNET (top left), CASTNET for total NO3 (NO3+HNO3) (top right), IMPROVE (bottom left) and NADP (bottom right ) monitoring sites in the 12 km modeling

domain.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-35 Figure 3-15. Comparison of predicted and observed Organic Carbon (OC; top) and Elemental Carbon (EC; bottom) model performance at IMPROVE (left) and STN (right) monitoring sites in the 12 km modeling domain.F:\Denver_O3_2008\Reports\2006_Base_Case\Dra ft_Final\Sec3_MPE_Diag1.doc August 2008 

### 3-36 3.5 DIAGNOSTIC MODEL PE RFORMANCE CONCLUSIONS

The diagnostic model performance evaluation provi des additional support that the Denver JuneJuly 2006 modeling database is wo rking sufficiently well for projecting future year changes in ozone concentrations in response to changes in em issions. It has also id entified areas of further analysis and refinement can be achieved to obt ain a better photochemical modeling database.

The mostly good agreement between the pred icted and observed VOC/NOx ratios at the metropolitan Denver sites suggests that we are ch aracterizing the on-road mobile sources well and capturing the correct chemical regimes in De nver. However, the comparisons for ethane and paraffin at the Denver sites, and especially th e Weld County sites, s uggest that natural gas emission sources are likely understated. In addi tion, the VOC speciation is an area that should be reviewed in the future with the model generally underestimating carbonyls (e.g., formaldehyde).

The ozone aloft performance evaluation was inco nclusive due to only having six comparisons

available. But the results do lend credence to th e hypotheses that the model is not predicting as high ozone aloft that is brought to the ground through vertical mixing. The PM evaluation was also inconclusive due to missing PM precursor emissions in the database, which is also an area for future improvements.F:\Denver_O3_2008\Reports\2006_B ase_Case\Draft_Final\Sec 4_Refs1.doc August 2008 

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### APPENDIX A

Comparison of Predicted and Observed Spa tial Distributions of the Daily Maximum

8-Hour Ozone Concentrations in the Denver Area during June-July 2006 for the Final CAMx 2006 Base Case (Run 17) Simulation

### Denver 2006 Base Case (run17.1204)