Modeling Protocol for the OTC CALGRID 

Screening-Level Modeling Platform for the 

Evaluation of Ozone, Fine Particulate Matter, and 

Regional Haze 

December 29, 2009 

New Hampshire Department of Environmental Services 

Air Resources Division 

29 Hazen Drive 

Concord, NH 03302
1 

1.0 Introduction

The Ozone Transport Commission (OTC) has sponsored the development of a 

photochemical modeling system to assist states in the preparation of their State 

Implementation Plans (SIPs) for attaining the eight-hour National Ambient Air Quality 

Standard (NAAQS) for ozone. The Community Multiscale Air Quality Model (CMAQ) 

is the basis of the OTC SIP-quality modeling platform that is being used in states’ eighthour ozone attainment SIPs. CMAQ was also an important analysis tool in states' SIPs 

for regional haze. It was used to assess source contributions to regional haze and to 

evaluate the effectiveness of control strategies for the mitigation of future visibility 

impairment. 

Running the CMAQ modeling platform is very resource intensive and usually requires 

the use of a Unix-based operating system. Therefore, the CMAQ modeling that is being 

done in support of the eight-hour ozone and regional haze SIPs is limited to a handful of 

modeling centers that have the necessary expertise and computer resources. Similarly, 

because of the substantial effort, time, and storage space required to run the SIP-quality 

CMAQ platform, it is impractical to assess a large number of run scenarios. 

Consequently, OTC sponsored the development of an additional grid-based 

photochemical modeling platform that states could use as a screening tool for running 

additional emissions control strategies or performing sensitivity runs. The requirements 

for this additional modeling platform were that it be flexible, portable, and easily 

accessible to agencies that wish to use it. In this manner, a larger number of run 

scenarios could be modeled, allowing states to screen a wider variety of potential control 

strategies. 

The California Grid Model (CALGRID) was selected as the basis of this screening 

platform. CALGRID is a grid-based photochemical modeling platform that is designed 

to be run in a Windows environment. CALGRID has recently undergone a series of 

improvements and enhancements, with the most recent version being designated 

CALGRID Version 2.45. CALGRID Version 2.45 is being used as the screening 

platform for the OTC eight-hour ozone attainment SIPs. CALGRID is also being used in 

screening-level analyses for fine particulate matter (particulate matter with an equivalent 

aerodynamic diameter of 2.5 microns or less, also known as PM2.5) and regional haze. 

This document outlines the manner in which CALGRID will be used in these efforts. 

2.0 Platform Description and Model Inputs

To make the CALGRID modeling platform the best possible tool to supplement the SIPquality CMAQ platform, it was decided that CALGRID would be run on the same 

modeling domain using a common set of model inputs. All boundary conditions, 

meteorology, and emissions inputs were the same as those used for the SIP-quality 

CMAQ platform. Processing programs were written to convert these inputs into a format 

useable by the CALGRID model. The modeling domain and model inputs are described 

in the sections below. 
2 

2.1 Modeling Domain

The OTC CMAQ/CALGRID modeling domain was set up on a Lambert Conic 

Conformal projection and covers the eastern United States and parts of Canada. The 

southwest corner of the domain was set at 264 km, -888 km and the northeast corner was 

set to 2328 km, 1176 km. A 12-km grid cell resolution was used with 172 grid cells in 

the east-west direction and 172 grid cells in the north-south direction. For the vertical 

grid definition, 22 layers were used in the CMAQ simulations. For CALGRID, the 

processing programs that were used to reformat the boundary conditions, meteorology, 

and emissions mapped the 22 layers used for CMAQ to a total of nine vertical layers for 

the CALGRID modeling. The OTC CMAQ/CALGRID modeling domain is shown in 

Figure 1. 

Figure 1: Map of the OTC CMAQ/CALGRID Modeling Domain

0 20 40 60 80 100 120 140 160

0

20

40

60

80

100

120

140

160
3 

2.2 Boundary Conditions 

For the OTC CMAQ modeling, boundary conditions were derived from GEOS-Chem 

(Goddard Earth Observing System) global atmospheric simulations by running CMAQ 

on the 36-km continental grid. For the CALGRID platform, initial conditions, side 

boundary conditions, and top layer concentrations were derived from the CMAQ 

boundary conditions files by means of a processing program. This program mapped the 

22 vertical layers used in the CMAQ simulations to the nine layers used with CALGRID. 

It produced the necessary side boundary file and top layer concentration file for each 

modeled episode day. It also produced an initial conditions file for each episode day 

processed; these files could be retained so that the user could begin a CALGRID 

simulation on any desired episode day. 

2.3 Meteorology

The meteorological modeling that was done in support of the OTC CMAQ SIP-quality 

modeling platform was performed by the University of Maryland (UMD) in conjunction 

with staff at the New York State Department of Environmental Conservation (NYSDEC). 

UMD used the Penn State/National Center for Atmospheric Research 5th Generation 

Mesoscale Model (MM5) Version 3.6 to generate year 2002 meteorological inputs. The 

details of this work are described in NYSDEC’s Technical Support Document TSD-1a, 

Meteorological Modeling Using Penn State/NCAR 5th Generation Mesoscale Model 

(MM5), February 1, 2006. For the CALGRID modeling platform, a processing program 

was used to interpolate the MM5 outputs to the CALGRID modeling grid and map them 

to CALGRID’s vertical layer structure. QA/QC plots were generated during the 

processing to ensure the accuracy of the interpolated data. Figures 2 through 4 show 

example QA/QC plots from the re-formatting of the meteorological data. 
4 

Figure 2: QA/QC Plot of Humidity Data

August 6, 2002 Hour 12

Humidity Layer 1

CALGRID 2.45 Modeling Domain

Humidity (ppm)

NHDES

7/18/06

400 600 800 1000 1200 1400 1600 1800 2000 2200

LCC Easting (km)

-800

-600

-400

-200

0

200

400

600

800

1000

LCC Northing (km)

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

26000

28000

30000

Figure 3: QA/QC Plot of Temperature Data

August 6, 2002 Hour 18

Temperature Layer 1

CALGRID 2.45 Modeling Domain

Temp (K)

NHDES

7/23/06

400 600 800 1000 1200 1400 1600 1800 2000 2200

LCC Easting (km)

-800

-600

-400

-200

0

200

400

600

800

1000

LCC Northing (km)

0

280

282

284

286

290

292

294

296

298

300

302

304

306

308

310
5 

Figure 4: QA/QC Plot of Rainfall Data

August 12, 2002 Hour 17

Rain

CALGRID 2.45 Modeling Domain

Rain (inches)

NHDES

7/17/06

400 600 800 1000 1200 1400 1600 1800 2000 2200

LCC Easting (km)

-800

-600

-400

-200

0

200

400

600

800

1000

LCC Northing (km)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

2.4 Emissions 

The Regional Planning Organizations (RPOs) and their contractors were responsible for 

preparing modeling emissions inventories for use in the OTC CMAQ SIP-quality 

modeling. The RPOs prepared a set of accurate, up-to-date, and quality assured 

emissions inventories for the 2002 Base Case and three future years, 2009, 2012, and 

2018. For the future years, emissions inventories were prepared for two emissions 

control scenarios: one reflecting those emissions controls that are in place or likely to be 

in place by 2009, and another that reflects additional control strategies that may be 

needed to demonstrate attainment with the eight-hour ozone standard. The first scenario 

is referred to as “On The Books/On The Way” (OTB/OTW), and the second is referred to 

as “Beyond On The Way” (BOTW). A third scenario, sometimes referred to as "Best & 

Final", was developed to assess additional potentially reasonable control programs aimed 

at improving visibility. All of these inventories were broken down into the following 

general emissions source categories: biogenic, point, area, non-road mobile, and on-road 

mobile. 

Using these inventories, NYSDEC and the other modeling centers, the Virginia 

Department of Environmental Quality (VADEQ) and Northeast States for Coordinated 

Air Use Management (NESCAUM), generated the necessary emissions inputs for CMAQ 

using the Sparse Matrix Operator Kernel Emissions (SMOKE) model. For the 

CALGRID modeling effort, the pre-merged SMOKE emissions files were obtained from 

the modeling centers and re-formatted for input into EMSPROC, the emissions pre-
6 

processor for the CALGRID modeling system. The pre-merged SMOKE files that were 

obtained from the modeling centers were broken down into the biogenic, point, area, nonroad, and on-road categories mentioned earlier. These files by component were then 

converted for use with EMSPROC, thus giving users of the CALGRID modeling system 

the flexibility to analyze a wide variety of emissions control strategies. QA/QC plots 

were generated during the re-formatting of the emissions data to ensure that an accurate 

modeling inventory was generated for the CALGRID platform. Example emissions 

QA/QC plots are shown in Figures 5 through 8. 

Figure 5: QA/QC Plot of Surface Source CO Emissions
7 

Figure 6: QA/QC Plot of Surface Source VOC Emissions

Figure 7: QA/QC Plot of Point Source NOx Emissions
8 

Figure 8: QA/QC Plot of Point Source SO2 Emissions

3.0 CALGRID Model Outputs

A variety of post-processing programs have been developed to assist users of the 

CALGRID modeling platform in visualizing and tabulating model results. These postprocessors are designed to take the hourly concentration output generated by the 

CALGRID model and produce statistical results for desired averaging periods and 

geographic areas. CALGRID can also generate output suitable for plotting with standard 

graphical packages such as the Center for Ocean-Land-Atmosphere Studies’ Grid 

Analysis and Display System (GrADS) or Golden Software’s SURFER. 

As with the CMAQ SIP-quality modeling platform, it was decided that the CALGRID 

screening results should be used in a relative manner. Ratios of model-predicted base 

case and future scenario concentrations would be applied to current monitored ozone 

design values to generate estimated future design values (DVFs) for the future-year 

scenario of interest. It is these DVFs that are used in the determination of attainment. 

4.0 Episode Selection

For the CMAQ SIP-quality ozone modeling analysis, the five-month ozone season of 

2002 was selected for modeling because it met EPA’s episode selection criteria of 

containing episode days that are meteorologically representative of typical high ozone 

exceedance days and that are severe enough that any control strategy that is predicted to 

reach attainment on those days would reach attainment on other less severe days. 
9 

Similarly, the CALGRID screening platform was run for the summer period from May 15 

to September 15, 2002 for the 2002 Base Case and 2009 OTB/OTW and BOTW 

scenarios. However, running the full summer episode, even with the CALGRID 

screening platform, is very time-consuming and resource intensive. In order to increase 

production and maximize the number of scenarios that can be evaluated with the 

CALGRID screening platform, it was decided that shorter modeling episodes would be 

selected that adequately reproduced the results obtained by running the full summer 

episode. An extensive analysis was undertaken to run a number of shorter summer 

episodes and compare the resulting predicted DVFs with those obtained for the full 

summer episode. The 2002 Base Case and 2009 OTB/OTW scenarios were used in this 

evaluation. It was found that the combined DVFs calculated from the July 6 to July 23, 

2002 and July 30 to August 16, 2002 modeling episodes best represented those from the 

full summer episode (note that July 6th and July 30th are considered to be model warm-up 

days). 

5.0 CALGRID Model Performance Evaluation

A qualitative and quantitative assessment was made of the CALGRID screening 

platform’s ability to reproduce observed ozone, PM2.5, and visibility. To assess its 

performance, the CALGRID screening platform was run for the 2002 Base Case for the 

July 30 to August 16, 2002 modeling episode. Predicted maximum eight-hour ozone 

concentrations at monitor locations were compared against observations for 2002. 

Comparisons were also made of predicted vs. observed PM2.5 and regional haze. All of 

these comparisons are described below and shown in the subsequent figures. 

Figure 9 shows the relative bias between maximum eight-hour ozone observations and 

predicted CALGRID eight-hour ozone concentrations for the 2002 Base Case for the 

episode from July 30 through August 12. Figures 10 through 13 show plots of predicted 

2002 Base Case ozone concentrations against 2002 observations for selected episode 

days. Although the CALGRID model has a tendency to over-predict, especially in the 

urban core areas of northern Virginia, Maryland, southeastern Pennsylvania, New York 

City and Boston, it does a reasonable job of reproducing the pattern of the 2002 

maximum ozone observations. 

Figures 14 through 19 present predicted maximum 24-hour PM2.5 concentrations (top of 

each figure) against observations (bottom of each figure) for selected episode days. 

Included for comparison are corresponding maximum PM2.5 concentrations predicted 

with the Regional Modeling System for Aerosols and Dispersion (REMSAD). 

Observations include measurements taken at monitors in the IMPROVE network 

(Interagency Monitoring of Protected Visual Environments). These figures show that 

CALGRID reasonably reproduces the pattern of maximum daily PM2.5 observations and 

provides a similar pattern of predictions as REMSAD, which is state-of-the-science 

model for predicting particulate matter and other pollutants. 
10 

Figure 20 compares predicted haze index (bottom of figure) with observations at 

IMPROVE sites (top of figure) for a relatively clear episode day (May 14th). Figure 21 

compares predicted haze index with observations for a relatively hazy day (August 12th). 

Lastly, Figures 22 through 28 show time-series plots of predicted vs. observed haze index 

for selected days and Class I areas. 

Figure 9: Relative Bias Between Maximum 8-hour Ozone Concentrations Predicted 

with CALGRID and Observations

Relative Bias (CALGRID minus Observed)

 -20 to -15

 -15 to -10

 -10 to -5

 -5 to -2

 -2 to 2

 2 to 5

 5 to 10

 10 to 15

 15 to 20

 20 to 50

Based on Model Data for 

July 30 - August 12, 2002

2002 Base Case Emissions

versus Observed Data

Green Circles are where

CALGRID Underpredicts

Red Triangles are where

CALGRID Overpredicts

NHDES 11/21/06
11 

Figure 10: Comparison of Maximum 8-hour Ozone Concentrations for August 11, 

2002

 

Maximum 8-Hour Ozone Concentrations

CALGRID - 2002 Base Case

OTC Modeling Domain - August 11, 2002

Ozone

Concentrations

(PPB)

NHDES

11/21/06

 0 to 40

 40 to 50

 50 to 60

 60 to 70

 70 to 80

 80 to 90

 90 to 100

 100 to 150

Figure 11: Comparison of Maximum 8-hour Ozone Concentrations for August 12, 

2002

Maximum 8-Hour Ozone Concentrations

CALGRID - 2002 Base Case

OTC Modeling Domain - August 12, 2002

Ozone

Concentrations

(PPB)

NHDES

11/21/06

 0 to 40

 40 to 50

 50 to 60

 60 to 70

 70 to 80

 80 to 90

 90 to 100

 100 to 150
12 

Figure 12: Comparison of Maximum 8-hour Ozone Concentrations for August 13, 

2002

Maximum 8-Hour Ozone Concentrations

CALGRID - 2002 Base Case

OTC Modeling Domain - August 13, 2002

Ozone

Concentrations

(PPB)

NHDES

11/27/06

 0 to 40

 40 to 50

 50 to 60

 60 to 70

 70 to 80

 80 to 90

 90 to 100

 100 to 150

Figure 13: Comparison of Maximum 8-hour Ozone Concentrations for August 14, 

2002

Maximum 8-Hour Ozone Concentrations

CALGRID - 2002 Base Case

OTC Modeling Domain - August 14, 2002

Ozone

Concentrations

(PPB)

NHDES

11/27/06

 0 to 40

 40 to 50

 50 to 60

 60 to 70

 70 to 80

 80 to 90

 90 to 100

 100 to 150
13 

Figure 14: Comparison of Maximum 24-hour PM2.5 Concentrations for July 31, 

2002 

July 31, 

2002

REMSAD

1

5

10

15

20

25

30

35

40

50

60

PM2.5

Concentrations

(UG/M3)

0 - 4

5 - 9

10 - 14

15 - 19

20 - 24

25 - 29

30 - 34

35 - 39

40 - 49

50 - 59

>= 60

CALGRID

Observations

IMPROVE
14 

Figure 15: Comparison of Maximum 24-hour PM2.5 Concentrations for August 

3, 2002 

August 3, 

2002

REMSAD

1

5

10

15

20

25

30

35

40

50

60

PM2.5

Concentrations

(UG/M3)

0 - 4

5 - 9

10 - 14

15 - 19

20 - 24

25 - 29

30 - 34

35 - 39

40 - 49

50 - 59

>= 60

CALGRID

Observations

IMPROVE
15 

Figure 16: Comparison of Maximum 24-hour PM2.5 Concentrations for August 

6, 2002

August 6, 

2002

REMSAD

1

5

10

15

20

25

30

35

40

50

60

PM2.5

Concentrations

(UG/M3)

0 - 4

5 - 9

10 - 14

15 - 19

20 - 24

25 - 29

30 - 34

35 - 39

40 - 49

50 - 59

>= 60

CALGRID

Observations

IMPROVE
16 

Figure 17: Comparison of Maximum 24-hour PM2.5 Concentrations for August 

9, 2002

August 9, 

2002

REMSAD

1

5

10

15

20

25

30

35

40

50

60

PM2.5

Concentrations

(UG/M3)

0 - 4

5 - 9

10 - 14

15 - 19

20 - 24

25 - 29

30 - 34

35 - 39

40 - 49

50 - 59

>= 60

CALGRID

Observations

IMPROVE
17 

Figure 18: Comparison of Maximum 24-hour PM2.5 Concentrations for August 

12, 2002

August 12, 

2002

REMSAD

1

5

10

15

20

25

30

35

40

50

60

PM2.5

Concentrations

(UG/M3)

0 - 4

5 - 9

10 - 14

15 - 19

20 - 24

25 - 29

30 - 34

35 - 39

40 - 49

50 - 59

>= 60

CALGRID

Observations

IMPROVE
18 

Figure 19: Comparison of Maximum 24-hour PM2.5 Concentrations for August 

15, 2002

August 15, 

2002

REMSAD

1

5

10

15

20

25

30

35

40

50

60

PM2.5

Concentrations

(UG/M3)

0 - 4

5 - 9

10 - 14

15 - 19

20 - 24

25 - 29

30 - 34

35 - 39

40 - 49

50 - 59

>= 60

CALGRID

Observations

IMPROVE
19 

Figure 20: Comparison of Observed and Predicted Haze Index for May 14, 2002

Observed Haze Index at IMPROVE Monitors for May 14, 2002

(in Deciviews)

NHDES 10/5/07

CALGRID 172x172 

Modeling Domain

Haze Index

(in Deciviews)

 0 to 7

 7 to 14

 14 to 19

 19 to 30

 30 to 37

 37 to 39

 39 to 50

Visual Range

(in Kilometers)

400 to 200

200 to 100

100 to 60

60 to 20

20 to 10

10 to 8

8 to 4

Great Gulf:

Obs = 3

Pred = 0

Brigantine:

Obs = 19

Pred = 18

Shenandoah:

Obs = 16

Pred = 18

Lye Brook:

Obs = 3

Pred = 7

CALGRID Predicted Haze Index at Ozone Monitors for May 14, 2002

(in Deciviews)

NHDES 10/5/07

CALGRID 172x172 

Modeling Domain

Haze Index

(in Deciviews)

 0 to 7

 7 to 14

 14 to 19

 19 to 30

 30 to 37

 37 to 39

 39 to 50

Visual Range

(in Kilometers)

400 to 200

200 to 100

100 to 60

60 to 20

20 to 10

10 to 8

8 to 4
20 

Figure 21: Comparison of Observed and Predicted Haze Index for August 12, 2002

Observed Haze Index at IMPROVE Monitors for August 12, 2002

(in Deciviews)

NHDES 10/5/07

CALGRID 172x172 

Modeling Domain

Haze Index

(in Deciviews)

 0 to 7

 7 to 14

 14 to 19

 19 to 30

 30 to 37

 37 to 39

 39 to 50

Visual Range

(in Kilometers)

400 to 200

200 to 100

100 to 60

60 to 20

20 to 10

10 to 8

8 to 4

Acadia NP:

Obs = 28

Pred = 27

Great Gulf:

Obs = 33

Pred = 28

Brigantine:

Obs = 25

Pred = 27

Shenandoah:

Obs = 33

Pred = 25

Lye Brook:

Obs = 33

Pred = 25

CALGRID Predicted Haze Index at Ozone Monitors for August 12, 2002

(in Deciviews)

NHDES 10/5/07

CALGRID 172x172 

Modeling Domain

Haze Index

(in Deciviews)

 0 to 7

 7 to 14

 14 to 19

 19 to 30

 30 to 37

 37 to 39

 39 to 50

Visual Range

(in Kilometers)

400 to 200

200 to 100

100 to 60

60 to 20

20 to 10

10 to 8

8 to 4
21 

Figure 22: Comparison of Predicted and Observed Haze Index at Acadia National 

Park, ME

Predicted vs. Observed Haze Index at Acadia NP, ME for Selected Dates

0

5

10

15

20

25

30

35

1/14/20022/10/20023/15/20024/14/20025/14/20026/16/20027/13/20028/15/20029/14/2002

10/17/200211/16/200212/13/2002

Deciviews

Predicted

Observed

'

Figure 23: Comparison of Predicted and Observed Haze Index at Great Gulf 

Wilderness Area, NH 

Predicted vs. Observed Haze Index at Great Gulf Wilderness Area, NH for Selected Dates

-5

0

5

10

15

20

25

30

35

1/14/20022/10/20023/15/20024/14/20025/14/20026/16/20027/13/20028/15/20029/14/2002

10/17/200211/16/200212/13/2002

Deciviews

Predicted

Observed
22 

Figure 24: Comparison of Predicted and Observed Haze Index at Brigantine 

National Wildlife Refuge, NJ

Predicted vs. Observed Haze Index for Brigantine NWR, NJ for Selected Dates

0

5

10

15

20

25

30

35

1/14/20022/10/20023/15/20024/14/20025/14/20026/16/20027/13/20028/15/20029/14/2002

10/17/200211/16/200212/13/2002

Deciviews

Predicted

Observed

Figure 25: Comparison of Predicted and Observed Haze Index at Addison Pinnacle, 

NY

Predicted vs. Observed Haze Index at Addison Pinnacle, NY for Selected Dates

0

5

10

15

20

25

30

1/14/20022/10/20023/15/20024/14/20025/14/20026/16/20027/13/20028/15/20029/14/2002

10/17/200211/16/200212/13/2002

Deciviews

Predicted

Observed
23 

Figure 26: Comparison of Predicted and Observed Haze Index at Arendtsville, PA

Predicted vs. Observed Haze Index at Arendtsville, PA for Selected Dates

0

5

10

15

20

25

30

35

1/14/20022/10/20023/15/20024/14/20025/14/20026/16/20027/13/20028/15/20029/14/2002

10/17/200211/16/200212/13/2002

Deciviews

Predicted

Observed

Figure 27: Comparison of Predicted and Observed Haze Index at Lye Brook, VT

Predicted vs. Observed Haze Index at Lye Brook, VT for Selected Dates

0

5

10

15

20

25

30

35

1/14/20022/10/20023/15/20024/14/20025/14/20026/16/20027/13/20028/15/20029/14/2002

10/17/2002

11/16/2002

12/13/2002

Deciviews

Predicted

Observed
24 

Figure 28: Comparison of Predicted and Observed Haze Index at Shenandoah, VA

Predicted vs. Observed Haze Index at Shenandoah, VA for Selected Dates

0

5

10

15

20

25

30

35

1/14/20022/10/20023/15/20024/14/20025/14/20026/16/20027/13/20028/15/20029/14/2002

10/17/200211/16/200212/13/2002

Deciviews

Predicted

Observed

6.0 CALGRID Model Runs

The OTC CALGRID modeling platform will be run for the 2002 Base Case, 2009 

OTB/OTB, and 2009 BOTW. These simulations will be run for the full summer (May 15 

to September 15, 2002) episode as well as for the shorter summer modeling episodes 

described earlier. A variety of control scenarios and sensitivity runs will be performed 

for the shorter episodes as requested by the OTC Modeling Committee or individual state 

agencies. The results of these runs may be used to evaluate, at a screening level, any 

additional emissions reductions that may be required, thus relieving the technical burden 

on the CMAQ modeling centers. CALGRID screening results may also be used in 

individual states’ weight-of-evidence (WOE) analyses. If states request it, the CALGRID 

modeling platform will be delivered so that they may run additional modeling scenarios 

at their discretion.