• Investigate possible causes

Intercontinental Transport and Chemical Transformation (ITCT)An International Global Atmospheric Chemistry (IGAC) Program

Ozone Trends along U.S. West CoastDavid Parrish - NOAA Aeronomy Laboratory

Goal: Investigate impact of continental emissions on downwind ocean and continents

• Demonstrate that ozone on U.S. West Coast has increased over last 20 years

Today:

• Discuss some implications

• Not a uniquely important region in terms of impact

• Several studies in North Pacific region over last 2 decades

Why focus on Asian Emissions, North Pacific and US West Coast?

30

25

20

15

10

5

0An

thro

po

ge

nic

NO

x E

mis

sio

ns

(Tg

/ye

ar)

20001995199019851980

North America

Asia+ 5.0 %/year

Europe

• Asian emissions increased significantly over period of studies - Look for parallel change in ambient levels

TrinidadHead2002

CheekaPeak

1997-2002

Pt. Arena1985

Pt. ReyesNationalSeashore

Springtime O3 Trends

RedwoodNational

Park

LassenVolcanicNational

Park

• Very few “background” data

Caveats:

• Relatively short records

• Strongest Asian outflow

Focus on Spring Season:

• Strongest trans-Pacific transport

• Most studies

2 aircraft studies: NASA CITE 1C in 1984 NOAA ITCT 2K2 in 2002

6 ground sites

70

60

50

40

30

20

O3 (pp

bv)

20001996199219881984

CITE 1C

ITCT 2K2

Lassen VolcanicNational Park

Elevated Data setsSites slope O3 2000 r2

(ppbv/yr) (ppbv)Lassen 0.46 ± 0.39 45.8 ± 2.4 0.36Aircraft 0.51 55.3

60

50

40

30

20

10

O3 (pp

bv)

20001996199219881984

Pt. Arena

TrinidadHead

Cheeka Peak

Point ReyesNational Sea Shore

RedwoodNational Park

Marine Boundary Layer Data Sets sites slope O3 2000 r2

(ppbv/yr) (ppbv) 4 sea-level 0.50 ± 0.36 39.9 ± 3.3 0.44 All 5 0.78 ± 0.28 42.9 ± 2.4 0.68

(Data selected to avoid North American influence)

Conclusion: Along the U.S. west coast, springtime O3 has increased by ≈ 0.5 ppbv/yr, i.e. ≈10 ppbv in 20 years or ≈1-1.5 %/yr

Increasing background ozone during spring on the west coast of North America, Jaffe et al., Geophys. Res. Letters, 30, 2003

Springtime mean O3 levels have increased

(Select marine air only)

45

40

35

30

807060504030O3 (ppbv)

45

40

35

30

-135 -130 -125 -120 -115 -110 -105

CITE 1C1984

ITCT-2K22002

• Two springtime aircraft studies

• Same dates, same region

Altitude dependence of springtime O3 increase

(Select marine air only)

Conclusion: Increase in O3

is seen at all altitudes. One indication that it is not strictly local effect.

8

6

4

2

0

altit

ude

abov

e su

rfac

e (k

m)

100806040200O3 (ppbv)

CITE 1C ITCT-2K2

• Two springtime aircraft studies

• Same dates, same region

Altitude dependence of springtime O3 increase

Ozone observations 1988-2001 from N.P.S. site at Lassen N.P.

(Analysis by Dan Jaffe, University of Washington, Bothell)

Seasonal dependence of O3 increase

Conclusion: O3 increase may be present in all seasons.

Do changes in background O3 matter?

Change in background O3

Small changes in background O3 make it harder for us to meet our air quality standard !

(Analysis by Dan Jaffe, University of Washington, Bothell)

Summer 2003: Record year for Siberian forest fires

Aircraft profile on June 2, 2003 found layers of enhanced smoke, carbon monoxide and ozone in these air masses.

Is there a connection with climate change?

(Analysis by Dan Jaffe, University of Washington, Bothell)

June 2003 Siberian forest fire impacted Seattle air quality June 6 at Enumclaw, Washington

Local pollution combined with LRT pushed this site over the air quality standard!

(Analysis by Dan Jaffe, University of Washington, Bothell)

Atmospheric Photochemistry Primer

CH4

VOC’sCO

CO2 + H2O

Emission Oxidation ofreduced C species

2O2

O3

Absence of NOx

destroys O3

HO2

OH

Radical chain chemistry performs oxidation

Production of hydroxyl radical

O3 O(1D) + O2

O(1D) + H2O 2OH

h

Presence of NOx

catalyzes O3

production

NO2

NO

O3

O2

h

Production of PAN

VOC’s + OH ….

…. + NO2 PAN

Transports NOx

H3C CO

O

O NO2

PA

N (

pp

bv)

2002200019981996199419921990198819861984

Cheeka Peak

Pt. A

ren

a

ITC

T 2

K2

PAN mediansslope = 3.8± 3.4 %/yr

r2 = 0.81

PAN meansslope = 3.0 ± 2.2 %/yr

r2 = 0.87

95%

83%

17%

mean

median

0.1

0.2

0.4

0.6

0.05

0.02

Conclusion: Along the U.S. west coast, springtime PAN has increased by ≈ 3-4 %/yr.Consistent with increasing Asian emissions.

Mean Springtime PAN levels have increased

Caveat: PAN levels are highly variable and available data are extremely limited

(ITCT 2K2 Aircraft data limited to marine boundary layer)

0.001

0.01

0.1

1

HC

(pp

bv)

Apr-25-1985 Apr-29-1985

10

2x101

3

4

5

6 O3 (ppbv)

Ethane Propane n_Butane

O3-3.0 -2.0 -1.0

ln (propane/ethane)

• Hydrocarbons and O3 vary together.

• Photochemical aging of Asian emissions largely responsible for variations.

0.001

0.01

0.1

1

HC

(pp

bv)

Apr-25-1985 Apr-29-1985

10

2x101

3

4

5

6 O3 (ppbv)

Ethane Propane n_Butane

O3 O3_HW

-3.0 -2.0 -1.0ln (propane/ethane)

• High northwest winds select for marine boundary layer air.

Conclusions from Pt. Arena Study:

(Parrish et al., JGR, 97, 15,883, 1992)

Pt. Arena

0.001

0.01

0.1

1

HC

(pp

bv)

Apr-25-2002 Apr-27-2002 Apr-29-2002

10

2x101

3

4

5

6 O3 (ppbv)

TrinidadHead

Similar HC variations, but O3 not nearly as affected.

70

60

50

40

30

20

10

0

O3

(pp

bv)

200220001998199619941992199019881986

max95%

83%

medianmean

17%

5%

min

Pt. Arena

Mean:0.50 ± 0.36

ppbv/yr

TrinidadHead

RedwoodNational Park

Point Reyes

95%:0.28 ± 0.41

ppbv/yr

5%:0.84 ± 0.67

ppbv/yr

O3 levels below 20 to 30 ppbv are much less likely now than in the mid- 1980’s

O3 increase greater at the lower levels

Atmospheric Photochemistry Primer

CH4

VOC’sCO

CO2 + H2O

Emission Oxidation ofreduced C species

Production of hydroxyl radical

O3 O(1D) + O2

O(1D) + H2O 2OH

h

Photochemical Clock

ethane + OH ….

propane + OH ….

≈40 days

≈10 days

As fresh emissions age, propane/ethane ratio decreases

Ratio insensitive to dilution

10

2x101

3

4

5

6

O3

(pp

bv)

-3.0 -2.5 -2.0 -1.5ln(propane/ethane)

Pt, Arenaslope = 0.86 ± 0.10

r = 0.86

O3 dependence on VOC aging

• In 2002 O3 was destroyed only slowly as VOC’s aged

20

40

50

60

30

O3 (

ppbv

)

• In 1985 O3 was destroyed efficiently as VOC’s aged

-3.0 -2.5 -2.0 -1.5ln(propane/ethane)

10

2x101

3

4

5

6

O3

(pp

bv)

Pt, Arenaslope = 0.86 ± 0.10

r = 0.86

ITCT 2K2 WP-3Dslope = 0.19 ± 0.06

r = 0.49

Conclusion: As Asian NOx

emissions have increased, Pacific photochemistry has become less efficient at destroying O3

(Select marine air only)

Summary: In springtime

Impact of Asian Emissions on the Photochemistry of the North Pacific Troposphere

• Asian emissions have increased by ≈ 5% / year over last 20 years

• O3 levels in Eastern Pacific have increased by ≈ 1-1.5 % / year

• PAN levels in Eastern Pacific have increased by ≈ 3-4 % / year

• Pacific photochemistry has become less efficient sink for O3

Caveat: Based on very few “background” data of short time span. 1985 Pt. Arena data are only early PAN and VOC measurements collected over 10 day period

Air Quality Control is beginning to have an international dimension

Implication

Acknowledgements

Ozone Measurements:

National Park Service Air Resources Division

NASA GTE Data Archive

PHOBEA - Jaffe et al.

PAN Measurements:

NCAR - Ridley et al.; Flocke et al.

SRI - Singh et al.

PHOBEA - Kotchenruther et al.

NOAA - Roberts et al.

Hydrocarbon Measurements:

NCAR - Atlas et al.

SRI - Singh et al.

10

2x101

3

4

5

6

O3

(ppb

v)

-3.0 -2.5 -2.0 -1.5ln(propane/ethane)

Pt, Arenaslope = 0.86 ± 0.10

r = 0.86

10

2x101

3

4

5

6

O3

(ppb

v)

5 6 7 8 90.1

2 3 4 5 6 7 8 91 propane (pptv)

Pt. Arena, 1985slope = 0.56 ± 0.05

r = 0.90

Propane concentration can substitute.

In the past 18 years, O3

decreases much less strongly with HC aging in spring in the Pacific MBL.

10

2x101

3

4

5

6

O3

(ppb

v)

5 6 7 8 90.1

2 3 4 5 6 7 8 91 propane (pptv)

Pt, Arenaslope = 0.56 ± 0.05

r = 0.90

Trinidad Headslope = -0.04 ± 0.06

r = -0.11

Hydrocarbon ratios provide a photo- chemical clock.

Can we find any other data similar to Pt. Arena?ITCT 2002 Aircraft data:

3.02.01.00.0log[n-butane (pptv)]

ITCT HC MBLsamples(< 1 km)

Select marine air only

-3.0 -2.5 -2.0 -1.5ln(propane/ethane)

10

2x101

3

4

5

6

O3

(pp

bv)

Pt, Arenaslope = 0.86 ± 0.10

r = 0.86

ITCT 2K2 WP-3Dslope = 0.19 ± 0.06

r = 0.49

Similar to Trinidad Head data

50

40

30

20

10240220200180160140120

3.02.01.00.0

Log[n-butane (pptv)]

TRACE-P HCDC-8 and P-3MBL > 25 N

aged

TRACE-P data: 2000

10

2x101

3

4

5

6

7

8

O3

(ppb

v)

-3.0 -2.5 -2.0 -1.5 -1.0ln(propane/ethane)

Pt, Arenaslope = 0.86 ± 0.10

r = 0.86

TRACE-Pslope = 0.40 ± 0.09

r = 0.58

Further south but also less O3 dependence

60

40

20

0

-20240220200180160140120

3.02.01.00.0

Log[n-butane (pptv)]

PEM West B HCDC-8

MBL < 25 Naged

PEM West B data:1994

5

6

7

8

910

2

3

4

5

6

O3

(ppb

v)

-3.0 -2.5 -2.0 -1.5 -1.0ln(propane/ethane)

Pt, Arenaslope = 0.86 ± 0.10

r = 0.86

PEM West-Bslope = 0.67 ± 0.12

r = 0.72

Similar to Pt. Arena, but largely tropical