1. Ozone Trends along U.S. West Coast
David Parrish - NOAA Aeronomy Laboratory
Intercontinental Transport and Chemical Transformation (ITCT)
An International Global Atmospheric Chemistry (IGAC) Program
Goal: Investigate impact of continental emissions on downwind
ocean and continents
Today:
Policy – Everyone is downwind from someone, even their own selves.
Asian are running an experiment for us:
Emission history
Trends on West coast
Demonstrate that ozone on U.S. West Coast has increased
over last 20 years
Discuss some implications
Investigate possible causes 1 1

2. Why focus on Asian Emissions, North Pacific and US West Coast?
Several studies in North Pacific
region over last 2 decades
Asian emissions increased
significantly over period of
studies - Look for parallel
change in ambient levels
Policy – Everyone is downwind from someone, even their own selves.
Asian are running an experiment for us:
Emission history
Trends on West coast
Not a uniquely important region
in terms of impact 2 2

3. Focus on Spring Season:
Springtime O3 Trends
Cheeka
Peak
Focus on Spring Season:
Strongest Asian outflow
Redwood
National Park
Strongest trans-Pacific transport
Lassen
Volcanic
National Park
Most studies
Trinidad
Head
2002
6 ground sites
2 aircraft studies:
NASA CITE 1C in 1984
NOAA ITCT 2K2 in 2002
Pt. Arena
1985
Very few “background” data
Caveats:
Relatively short records
Pt. Reyes
NationalSeashore 4 4

4. Springtime mean O3 levels have increased
Increasing background ozone during spring on the west coast of North America,
Jaffe et al., Geophys. Res. Letters, 30, 2003
(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 5 5

5. Altitude dependence of springtime O3 increase
Two springtime aircraft
studies
Same dates, same region
(Select marine air only) 9 9

6. Altitude dependence of springtime O3 increase
Two springtime aircraft
studies
Same dates, same region
Conclusion: Increase in O3
is seen at all altitudes.
One indication that it is
not strictly local effect.
(Select marine air only) 9 9

7. Ozone observations 1988-2001 from N.P.S. site at Lassen N.P.
Seasonal dependence of O3 increase
Ozone observations from N.P.S. site at Lassen N.P.
Conclusion: O3 increase
may be present in all
seasons.
(Analysis by Dan Jaffe, University of Washington, Bothell)

8. 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)

9. 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)

10. 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)

11. HO2 OH NO2 NO O3 O2 2O2 O3 Atmospheric Photochemistry Primer CH4 VOC’sCO
CO2 + H2O
Emission
Oxidation of
reduced C species
Production of hydroxyl radical O3
O(1D) + O2
O(1D) + H2O
2OH h
HO2 OH
Radical chain chemistry
performs oxidation
Presence of NOx
catalyzes O3
production
NO2 NO O3 O2 h
2O2 O3
Absence of NOx
destroys O3
Production of PAN
VOC’s + OH ….
…. + NO2
PAN
Transports NOx
H3C C O
NO2

12. Mean Springtime PAN levels have increased
Conclusion: Along the U.S.
west coast, springtime
PAN has increased by
≈ 3-4 %/yr.
Consistent with increasing
Asian emissions.
Caveat: PAN levels are
highly variable and
available data are
extremely limited
(ITCT 2K2 Aircraft data limited to marine boundary layer)

13. O3 not nearly as affected. Pt. Arena
High northwest winds select for
marine boundary layer air.
Trinidad
Head
Similar HC variations, but
O3 not nearly as affected.
Conclusions from Pt. Arena Study:
(Parrish et al., JGR, 97, 15,883, 1992)
Hydrocarbons and O3 vary together.
Photochemical aging of Asian
emissions largely responsible
for variations.
Pt. Arena

14. O3 increase greater at the lower levels
O3 levels below 20 to 30
ppbv are much less likely
now than in the mid-
1980’s

15. Atmospheric Photochemistry Primer
VOC’s CO
CO2 + H2O
Emission
Oxidation of
reduced C species
Production of hydroxyl radical O3
O(1D) + O2
O(1D) + H2O
2OH h
Photochemical Clock
ethane + OH ….
propane + OH
t ≈ 40 days
t ≈ 10 days
As fresh emissions age,
propane/ethane ratio decreases
Ratio insensitive to dilution

16. O3 dependence on VOC aging
Conclusion: As Asian NOx
emissions have increased,
Pacific photochemistry has
become less efficient at
destroying O3 60 50
In 1985 O3 was destroyed
efficiently as VOC’s
aged 40
In 2002 O3 was destroyed
only slowly as VOC’s
aged
O3 (ppbv) 30 20
(Select marine air only)

17. Impact of Asian Emissions on the
Photochemistry of the North Pacific Troposphere
Summary: In springtime
Asian emissions have increased by ≈ 5% / year over last 20 years
O3 levels in Eastern Pacific have increased by ≈ % / year
PAN levels in Eastern Pacific have increased by ≈ 3-4 % / year
Policy – Everyone is downwind from someone, even their own selves.
Asian are running an experiment for us:
Emission history
Trends on West coast
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 10

18. National Park Service Air Resources Division
Implication
Air Quality Control is beginning to have an international dimension
Acknowledgements
Ozone Measurements:
National Park Service Air Resources Division
NASA GTE Data Archive
PHOBEA - Jaffe et al.
PAN Measurements:
Hydrocarbon Measurements:
NCAR - Ridley et al.; Flocke et al.
NCAR - Atlas et al.
SRI - Singh et al.
SRI - Singh et al.
PHOBEA - Kotchenruther et al.
NOAA - Roberts et al.

20. Propane concentration
can substitute.
In the past 18 years, O3
decreases much less
strongly with HC aging
in spring in the Pacific
MBL.
Hydrocarbon ratios
provide a photo-
chemical clock.

21. Can we find any other data similar to Pt. Arena?
ITCT 2002 Aircraft data:
ITCT HC MBL
samples
(< 1 km)
Select marine air only
Can we find any other data similar to Pt. Arena?
Similar to Trinidad Head data

22. Further south but also less O3 dependence
TRACE-P data:
2000
Further south but also less O3 dependence
TRACE-P HC
DC-8 and P-3
MBL > 25 N
aged

23. Similar to Pt. Arena, but largely tropical
PEM West B data:
1994
Similar to Pt. Arena, but largely tropical
PEM West B HC
DC-8
MBL < 25 N
aged