Evaluation of the Accuracy o

MM5/CALMET Generated 

Wind Fields in Southwestern 

Wyoming

D.N. Blewitt, CCM

Comments on behalf of the 

American Petroleum Institute
Importance of Accurate 

Meteorological Modeling 

Results

• For conducting regional air quality analyses 

AQRVs and ozone, accurate meteorological modeling results are imperative

• Because Class I Areas are a concern, accura

estimates of wind direction are necessary

• Because of the importance of chemical reac

accurate estimates of wind speed are necess
Bridger Class I Area

Jonah Met TowerSalt Mt. Range

Southwest Wyoming Geography
MM5 Results Available fo

CALMET Input

• MM5 was run as part of the SWWYTAF an

using a 36 kilometer grid for the year 1995 (EarthTech, 2001The Southwest Wyoming Regional CALPUFF Air Quality Modeling 

• MM5 was run for 2002 using a 12 kilomete

(Bureau of Land Management, 2007, Moxa Area Infill Gas Development Project)

• MM5 was run for for Southwest Wyoming 

year 2006 using a 4 kilometer grid – CALMwas not run (Environ 2008)
36 and 12 Kilometer CALM

Analysis

• MM5 was used as the initial guess fiel

CALMET

• In addition to MM5, CALMET used 2

surface stations and 5 upper air station

• The modeling domain was 464 km (ea

west) by 400 km (north-south)

• The grid size used in CALMET was 4 

kilometers 
Jonah Meteorological Da

• Data collected 1999 to 2004• 10-meter tower 

– Wind speed– Wind direction– Temperature– Sigma theta

• Data recovery in excess of 99 percent• QA/QC calibrations and audits performed 

according to EPA Guidelines


Analysis Technique 

• CALMET was run and ISC met data sets fo

Jonah and Lander sites were extracted

• Compared extracted wind rose to measured 

rose

• Comparison between MM5/CALMET is ba

pairing in space but not time

• Operational evaluation • Qualitative comparison of model output to 

monitored data 
Jonah MM5/CALMET

Predicted

Jonah Obser

36 Kilometer Comparison
0 100 200 300 400

MM5 Wind Direction (Deg)

0

100200300400

CALMET Wind Direction (Deg)

Figure 11. MM5 wind Direction vs Calmet for Wind Speeds > 1.0 m/sNote: Every 10th point is plotted

Comparison of MM5 Wind Direction to CALMET Win

36 Kilometer MM5 Run
0 1 2 3 4 5 6 7 8 9 10 11 12 13

Wind Speed Class (m/S)

0

10203040

Frequency of Occurance (%)

Measured Wind SpeedCalmet Level 1( 10-meter) Wind Speed

Comparison of Frequency of Occurance of Measured WindSpeed and Calmet Extracted Wind Speed for the Same Location and All Stabilities
NORTH

SOUTH

WEST EAST

5%

10%

15%

20%

25%

WIND SPEED(Knots)

>= 2217 - 2111 - 177 - 114 - 71 - 4

Calms: 5.77%

NORTHSOUTH

WEST 

5%

10%

15%

20%

2

Jonah CALMET/MM5 Predicted Jonah Measured

12 Kilometer Comparison
NORTH

SOUTH

WEST EAST

5%

10%

15%

20%

25%

WIND SPEED(Knots)

>= 2217 - 2111 - 177 - 114 - 71 - 4

Calms: 5.77%

Jonah CALMET/MM5 Predicted

12 Kilometer Comparison
Comparison of Measured and Modeled W

Speeds (12 Kilometer MM5) at Jonah

05

1015202530354045

Calm 0.5-2.1 2.1-3.6 3.6-5.7 5.7-8.8 8.8-11.1 >11.1

Wind Speed (m/s)

Frequency (%) Me

Mo
4 Kilometer MM5 Jonah (2006) Observed Jonah 

Source: Environ

4 Kilometer Comparison
4 Kilometer MM5 4 Wamsutter (2006) Observed Wamsutter Mo

Source: Environ

4 Kilometer Comparison
NORTH

SOUTH

WEST EAST

5%

10%

15%

20%

25%

WIND SPEED(Knots)

>= 2217 - 2111 - 177 - 114 - 71 - 4

Calms: 5.77%

Comparison of 4 kilometer MM5, 

12 and 36 Kilometer MM5/CALMET Windroses for 
Conclusions and Recommenda

The widespread use of meteorological model o

in air quality modeling requires:

• The accuracy of MM5/CALMET model output mu

tested for each dispersion model application

• EPA needs to coordinate a stakeholder group to dev

guidelines for the use of meteorological models in quality analyses

• Meteorological model accuracy is more important t

number of years of model results used in an air quaanalysis
Conclusions and 

Recommendations (continu

Topics that the modeling community need to 

address:

– Which meteorological model should be used?– Grid size?– How should meteorological monitoring sites be 

included in modeling?

– Model performance criteria?