Brian Eder, Alfreida Torian, James Godowitch, Thomas Pierce and Steve Howard

Brian Eder, Alfreida Torian,James Godowitch, Thomas Pierce and Steve Howard

Emission and Modeling Evaluation BranchAtmospheric Modeling and Analysis Division

National Exposure Research Laboratory,U. S. EPA RTP, NC 27711

Presented at the 8th Annual CMAS Conference, Chapel Hill, NC October 21, 2009

An Evaluation of CMAQ’s Performancein the PBL and Free Troposphere

Using Ozonesondes

Because of the dearth of upper-air measurements, evaluation of CMAQ’s ability to simulate O3 mixing ratios has historically focused on surface performance.

These evaluations take advantage of extensive data sets offered by networks like CASTNet and EPA’s AQS.

While such analyses are essential in understanding and subsequently improving the model’s performance, it is increasingly important to examine the model’s ability to simulate conditions aloft:

- Planetary Boundary Layer (PBL): surface to 1000 - 3000 m

- Free Troposphere (FT): 1000 - 3000 m to tropopause

Motivation

Motivation

This increased emphasis of CMAQ’s ability to properly simulate ozone aloft is due in part to recent revisions of the NAAQS.

Such revisions have resulted in increased scrutiny on CMAQ’s ability to accurately simulate both:

- transport aloft, whether it be regional, continental or even hemispheric

- the “background” or natural component of ozone, including ozone originating from stratospheric intrusions associated with tropopause folds.

Accordingly, this research will utilize data obtained from four sites:

- Trinidad Head, CA (41.070 N, 124.150 W)- Boulder, CO (40.020 N, 105.270 W)- Huntsville, AL (34.730 N, 86.580 W)- Wallops Island, VA (37.900 N, 75.500 W)

in order to evaluate CMAQ’s ability to simulate:

- Ozone mixing ratios (ppm)- Temperature (0 C)- Relative Humidity (%)

in the PBL and FT.

This analysis covers the summer months (J, J, A) from 2002 - 2006.

Response

Version: v.4.7 as configured for CDC PHASE runs for period 2002-2006

Emissions: Processed using SMOKE and based on the 2002 NEI (w/year-specific fire, mobile, biogenic and points EGU data).

Chemistry: CB05

Meteorology: MM5

LBCs: Month-specific derived from a 2002 GEOS - Chem simulation

Resolution: 36 Km horizontal grid

24 vertical layers extending from the surface to 100 hPa.

CMAQ Attributes

Ozonesonde Observations

StationStation Lat.(o N)

Long.( o W)

Elev.(m asl)

Number

sondes

Trinidad Head, CASTN 445

41.07 124.15 20 135

Boulder, COSTN 67

40.02 105.27 1743 98

Huntsville, ALSTN 418

34.73 86.58 196 91

Wallops Island, VASTN 107

37.90 75.50 13 37

CMAQ Domain

Evaluation Protocol

CMAQ Layer Characteristics

Layer Bottom Middle Top Depth# (m agl) (m agl) (m agl) (m agl)

24 10,634 12,031 13,429 2,79523 8,583 9,608 10,634 2,05222 6,943 7,763 8,583 1,64021 5,566 6,255 6,943 1,37620 4,376 4,971 5,566 1,19219 3,323 3,849 4,376 1,05418 2,838 3,081 3,323 48517 2,378 2,608 2,838 46116 2,025 2,201 2,378 35315 1,768 1,896 2,025 25714 1,518 1,643 1,768 25013 1,355 1,437 1,518 16312 1,195 1,275 1,355 16011 1,038 1,116 1,195 15810 882 960 1,038 1559 730 806 882 1538 579 655 730 1507 431 505 579 1486 285 358 431 1465 213 249 285 724 142 178 213 723 71 106 142 712 35 53 71 351 0 18 35 35

Observations from each sonde were assigned to the appropriate CMAQ layer based on either:

- extrapolation in layers where no observations were available,

- weighted averaging when numerous observations were available.

Evaluation Protocol

Only ozonesondes launched during the afternoon, when the PBL was more likely to be well mixed, were used in the calculation of the evaluation statistics.

A suite of performance metrics were calculated, including the:

- Normalized Mean Error (NME) - Normalized Mean Bias (NMB),

which will be the metrics discussed.

N M BM odel O bs

O bs

N

N

( )

( )

1

1

100%

N M EM odel O bs

O bs

N

N

1

1

100%( )

Ozone

10

100

1000

10000

100000

-80 -60 -40 -20 0 20 40 60 80

NMB (%)

Heig

ht

(m

ag

l)

Wallops (n=37) Huntsville (n=91) Trinidad (n=135) Boulder (n=98)

Evaluation Results - NMB

Ozone

10

100

1000

10000

100000

-80 -60 -40 -20 0 20 40 60 80

NMB (%)

Heig

ht

(m

ag

l)



CMAQ greatly over-predicts ozone throughout the lower PBL at the two coastal sites, especially at Trinidad Head.

CMAQ performs well throughout

the most of the PBL at the two inland sites, especially at Boulder.

CMAQ consistently and increasingly under-predicts ozone in the upper portions of the FT, especially near the tropopause.

Ozone

10

100

1000

10000

100000

-80 -60 -40 -20 0 20 40 60 80

NMB (%)

Heig

ht

(m

ag

l)



CMAQ greatly over-predicts ozone throughout the lower PBL at the two coastal sites , especially at Trinidad Head.


most of the PBL at the two inland sites, especially at Boulder.


Ozone

10

100

1000

10000

100000

-80 -60 -40 -20 0 20 40 60 80

NMB (%)

Heig

ht

(m

ag

l)



CMAQ greatly over-predicts ozone throughout the lower PBL at the two coastal sites , especially at Trinidad Head.


the most of the PBL at the two inland sites, especially at Boulder.


Evaluation Results - NME

Ozone

10

100

1000

10000

100000

0 20 40 60 80 100

NME (%)

Heig

ht

(m

ag

l)


Good CMAQ performance

throughout the PBL and most of the FT at the two inland sites.

Performance at the coastal regions is worse.

Performance in the upper FT is poor at all locations.

O3 T RH O3 T RH

Evaluation Results – Trinidad Head, CA (n=135)

O3 T RH

Ozone is greatly over-predicted within the PBL.

Slightly under-predicted in the

lower FT.

Greatly underpredicted in the upper FT.

O3 T RH


O3 T RH

Temperature is over-predicted throughout most of the PBL.

Slightly under predicted in the lower FT and over-predicted in the upper FT.


O3 T RH

RH is underpredicted throughout the entire PBL.

Over-predicted in most of the FT.


O3 T RH

MM5-CMAQ do a poor job in representing the marine-PBL at this west coast location.

- Not surprising given the 36 km

resolution


O3 T RH

The underprediction in the FT, may be attributable to the lateral boundary conditions (LBC).

- Values provided by GEOS-

Chem, while representing an improvement over previously used static LBCs, may not be high enough.



Summer Boundary Conditions GEOS-CHEM (2002)

10

100

1000

10000

100000

0 20 40 60 80 100

Ozone (ppbv)

He

igh

t (m

a

gl)

North East South West

The underprediction in the FT, may be attributable to the lateral boundary conditions (LBC).

- Values provided by GEOS-

Chem, while representing an improvement over previously used static LBCs, may not be high enough.

O3 T RH

Ozone is over- predicted within 400 m of surface.

Fairly well predicted in the

remainder of the PBL

Underpredicted in the FT.

Evaluation Results – Wallops Island, VA (n=37)

O3 T RH

Temperature is slightly under-predicted within 100 m of the surface.

Well predicted in the remainder of the PBL and most of the FT.


O3 T RH

RH is over- predicted near the surface.

Slightly underpredicted in

the upper PBL and lower FT

Over-predicted in the upper FT.


O3 T RH


CMAQ does a better job in representing the marine-PBL at this east coast location.

Ozone performance is still fairly poor throughout the FT.

- Transport aloft may be

underrepresented.

- LBCs aloft may again be too low.

O3 T RH

Evaluation Results – Huntsville (n=91)

Ozone is slightly over- predicted within 100 m of surface.

Increasingly under-predicted in the

remainder of the PBL and FT.

O3 T RH


Temperature is well-predicted throughout the PBL and most of the FT.

O3 T RH O3 T RH


RH is slightly over- predictedin the PBL.

Slightly underpredicted in the

lower FT and over-predicted in the upper FT.

O3 T RH O3 T RH


CMAQ does a better job at representing the meteorology at this inland location – as expected.

Ozone performance is, however, increasing poor through most of the FT.

- Transport aloft may again be

underrepresented.

- Lack of lightning generated NOx emissions may be an issue.

Ozone is very well predicted within 400 m of surface.

Slightly under-predicted in the

remainder of the PBL and lower FT.

Greatly underpredicted in the upper FT.

O3 T RH

Evaluation Results – Boulder, CO (n=98)

Temperature is under-predicted throughout the PBL and lower FT.

Over-predicted in the upper FT.

O3 T RH


O3 T RH

CMAQ does a good job at predicting the ozone at this inland mountain location throughout the PBL and most of the FT.

Surprisingly though, CMAQ’s meteorological performance isnot quite as good.


CMAQ varies in its ability to accurately simulate ozone in the PBL and FT.

Summary

Over-predicts ozone throughout the lower PBL at the coastal sites, especially at Trinidad Head.

- Inability to accurately resolve marine boundary layers at a 36 km scale. Performs better throughout most of the PBL at the inland sites, especially at Boulder.

Tends to underpredict throughout much of FT at all sites.

- Poor representation of transport aloft, lack of lightning generated NOx

emissions and inaccurate LBCs are possible contributors.

Consistently and greatly under-predicts ozone in the upper portions of the FT, especially near the tropopause.

- Inaccurate representation of ozone originating from stratospheric intrusions associated with tropopause folds may be the cause.

Future Work - Case Studies Individual case studies are being developed that will provide a better understanding of CMAQ’s inconsistent performance in simulating ozone aloft.

- In a few instances, both morning and afternoon ozonesonde launches were conducted at the four sites.

- These consecutive launches will be examined to evaluate CMAQ’s ability to simulate, diurnally, the evolution of the PBL and FT.

Huntsville, AL2 July, 2005 18:19 UTC

CMAQ Ozonesonde

Thank you

Contact Information: [email protected] (v)919.541.1379 (f)

Disclaimer: Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

Documents

Brian Eder, Alfreida Torian, James Godowitch, Thomas Pierce and Steve Howard