1. OZONE AND ITS PRECURSORS OVER THE UNITED STATES:
SOURCES, OUTFLOW, TRANSPACIFIC INFLOW, AND HEMISPHERIC INFLUENCE
My thesis looks at ozone and its precursors over the U.S. in particular Asian inflow, sources over the U.S. , export from the BL, and the eventual hemispheric influence.
Rynda Hudman
Thesis Defense April 3, 2007

2. Hemispheric Pollution Direct Intercontinental Transport
Alt (km)
Intercontinental Influence of Ozone (1) primary constituent of smog in surface air [NRC, 1991] (2) 3rd most important greenhouse gas [IPCC, 2001] 10
Greenhouse gas 8 hn O3
NO2 NO 6
Hemispheric Pollution 4 OH
HO2
Ozone is produced in the atmosphere by the photochemical oxidation of VOCs in the presence of NOx.
We care about ozone because it is the primary constituent of smog at the surface, and the 3rd most important green house gas in the free troposphere.
Ozone formation in most of the atmosphere is limited by the supply of NOx.
So we care about ozone, NOx and its oxidation products when discussing the influence of ozone. There are two modes of intercontinental influence. 1st Direct Intercontinental Transport of pollutants either by direct boundary layer transport or uplift into the free troposphere, transport, followed by subsidence over the receptor region. 2nd is the impact on hemispheric pollution defining a hemispheric background, pollutants are vented out of the boundary layer, mix with free tropospheric air and impact the downwind continent by subsidence. Here I examine the U.S. sources, export and hemispheric influence of ozone and its precursors as well as Asian inflow into the United States.
Direct Intercontinental Transport
(1 week) 2
VOCs
Air quality
Air quality
CONTINENT 1
CONTINENT 2
OCEAN

3. RISING OZONE BACKGROUND AT NORTHERN MID-LATITUDES
Mountain sites in Europe
U.S. Pacific coastal sites
There is evidence that ozone in northern midlatitudes has risen in the past century and more specifically continues to rise. On the left is data from a mountain site in Europe which show a 1.6%/yr increase since 1890s with a larger increase since the early 1980s. On the right are a comparison of surface sites on the West Coast of the U.S. which show a linear trend 0.5 ppbv year, ~10 ppbv increase over the past 20 years. This illustrates the importance of having a good understanding of the anthropogenic contribution to hemispheric ozone. Here, I examine the U.S. contribution to background ozone, by aiming to understand precursor emissions and their export.
Marenco et al. [1994]
Jaffe et al. [2003]
What is North American impact on ozone from biomass burning, fossil fuels, and lightning?

4. SENSITIVITY OF SIMULATED SURFACE OZONE TO ANTHROPOGENIC EMISSIONS IN INDIVIDUAL CONTINENTS
N. America
Sept 1997
Europe
Qinbin Li in our group did sensitivity simulations to understand the background enhancements to surface ozone from the three major poles of NOx emissions in midlatitudes. The top is North America, we see a 3-5 ppbv enhancement over Europe, European contribution head to the Arctic and East. Anthropogenic Asian emissions enhance west coast ozone by 3-4 ppbv. This is lower than the predicted increase by Jaffe. So its unclear still what is causing this.
Asia
[Li et al., 2002]

5. DEPLETION OF OZONE BACKGROUND DURING REGIONAL POLLUTION EPISODES
Ozone (ppbv)
Cumulative Probability
Low-elevation CASTNet sites, Jun-Aug
CASTNet observations
GEOS-Chem model
Model background *
The influence of ozone background on ozone air quality over the U.S. has been well studied. Here I show work by Arlene Fiore showing the cumulative probability of ozone using castnet sites across the U.S.. Simulation of these data by GEOS-Chem, the model I also use, is shown in red. The model background, calculated by shutting off NA emission sources, is shown in green so that includes natural background + anthropogenic emissions from other continets. What we see is that during pollution episodes, background ozone is at a minimum due to loss during stagnation. So I am to understand how much does Asian pollution affect ozone air quality?
How much does Asian pollution affect ozone air quality in the United States?
Fiore et al., [2002]

6. SOURCES, OUTFLOW, TRANSPACIFIC INFLOW, AND HEMISPHERIC INFLUENCE
RESEARCH Questions:
INFLOW: How is ozone produced during transpacific transport of Asian pollution, and what are the implications for surface ozone air quality in the U.S.?
SOURCES and CHEMICAL EVOLUTION: How well constrained are U.S. CO and NOx sources from combustion and lightning? Can we relate the trend in the ozone-CO relationship in the U.S. boundary layer outflow to changes in OPE and emissions?
OUTFLOW AND INFLUENCE: How does NOx evolve in the U.S. boundary layer and what are the implications for NOx export? What is the impact of NA biomass burning, lightning and anthropogenic export on hemispheric ozone?
In my thesis I aim to answer the following questions:
In tems of inflow - Read 1.
Over the continent - Read 2.
NOx in the boundary layer is short lived, so how does it evolve and what for s this mean for export?
Finally, using the constraints above, what is the NA enhancement to hemispheric oxone.
To look at these questions, I make use of the GEOS-Chem model, a coupled ozone-NOc-VOC- aerosol model, run at 2x2.5 with assimuilated meteorology from GMAO at NASA. I use this model to interpret observations of ozone and its precursors during two major campaigns.
TOOL: GEOS-CHEM: 3-D coupled ozone-NOx-VOC-aerosol tropospheric Chemistry Model [Bey et al., 2001] (uses assim. met.; 2ºx2.5º horiz. resn., 43 tracers) to interpret aircraft observations of ozone and its precursors

7. MAJOR FINDINGS North America SOURCES AND EXPORT INFLOW SPRING 4 2 6 8
NOx stationary sources %
Anthropogenic CO % 4 2 6 8
Alt (km) 10
O3 (ppbv)
SOURCES AND EXPORT
BB NA FF Lightning
NOx/flash
4X larger than previously thought!
Export well constrained
 effects on O3 & OPE
SUMMER
INFLOW
Subsidence
Over E Pacific
Asian Plume
PANNOxHNO3 strong O3
Before I dive in, I want to summarize the major findings of my work and then go into detail on each one.
First for the inflow:
Asian pollution plumes are uplifted over the continent in cyclones in the spring, are transported quickly at 5-8 km. Some continue over the U.S. but others subside. We find that during subsidence PAN decomposition to form NOx is a major and possibly dominant component of ozone enhancement in these plumes. Strong dilution takes place as plumes entrain into the boundary layer reducing the impact on U.S. surface sites. California mountain sites, however, are more sensitive to Asian pollution because of their contact with the free troposphere.
Over the continent we used ICARTT observations to confirm decreases in stationary NOx sources over the U.S. from the NOx SIP Call which amounts to a 22% decrease in NOx emissions during the summer. We then look at resulting ozone decreases in terms of regional ozone production efficiency.
We find the anthropogenic CO source over the U.S. is over estimated by 60% making it less than the biogenic source in the summer. We find that the NOx oxidation in the BL and export to the free troposphere is well understood. At 3-4 km HNO3 dominates the export but at higher elevations PAN is dominant supporting evidence of a large source of ozone through PAN export.
We constrain NOx by lightning. It is a factor of 4 higher than what is previously thought and has a ppbv impact on ozone. We then use these constraints to get estimates on enhancements to the ozone over the U.S. and downwind. We find equal enhancements from lightning and FF in the upper troposphere.
X10 Dilution
 Asia
 Europe
North America

8. Northern Hemisphere Burden
MAJOR FINDINGS (2)
North American (NA) enhancement to Northern Hemisphere summertime ozone burden
Northern Hemisphere Burden
We find that simulated NA biomass emissions impact the European ozone background by 2-6 ppbv as large as the NA FF enhancement. Using all of these constraints gained we can provide new estimates on NA influence on global ozone. We find NA cenhances the ozone budget by 14%, with equal contributions from biomass and lightning.
2004 NA Biomass burning enhanced ozone 2-6 ppbv over Europe! 
 Asia
 Europe
North America

9. NOAA/ITCT-2K2 AIRCRAFT CAMPAIGN IN APRIL-MAY 2002 Monterey, CA
High-ozone Asian pollution plumes observed in lower free troposphere but not at surface (Trinidad Head)
May 5 plume at 6 km:
High CO and PAN,
no O3 enhancement O3 CO
PAN
To study Asian inflow I looked at aircraft observations from spring First, PEACE-B which took place over Japan and the NW Pacific and ITCT2k2 which took place at the same time off shore of California. A number of Asian pollution plumes where observed in the free troposphere, but there was no visible Asian ozone plumes observed the surface site at Trinidad Head. Here I am showing two free tropospheric plumes observed by the ITCT2k2 aircraft. 1st a plume was observed on May 5th at 6km altitude off the coast of Northern California. It was of Asian fossil fuel origin (based on backward trajectories and HCs within the plume). It was uplifted by a WCB in a cyclone to ~6km and quickly transported over the Pacific. It was enhanced in CO and in PAN but there was no ozone enhancement above the local ft background.
In contrast to the May 17th a plume. The plume was also uplifted in a cyclone over East Asia to ~ 6-7km altitude, mid-Pacific it the reached a weak high pressure ridge where it left the WCB and continued to slowly subside over the next 7 days to 2.5 km where it was observed offshore of Southern California. Similar to the May 5th plume it was of fossil fuel origin. It was enhanced in CO. But was depleted of PAN, total NOy was ~ the same. Comparing these plumes we fing the PAN had decomposed into NOx producing ~20 ppbv ozone in the subsiding plume. This corresponds to an ozone production efficiency per unit NOx of 53.
HNO3
May 17 subsiding
plume at 2.5 km:
High CO and O3,
PANNOxHNO3
Hudman et al. [2004]
Measurements (NOAA WP-3D):
T. Ryerson (O3, NOx), John Holloway (CO), Frank Flocke (PAN), Andy Neuman (HNO3)

10. CONCEPTUAL PICTURE OF OZONE PRODUCTION IN TRANSPACIFIC ASIAN POLLUTION PLUMES
GEOS-CHEM
Hudman et al. [2004]
Stratospheric
downwelling
Subsidence
Over E Pacific
Gross OPE 60-80,
low OH
PANNOxHNO3
Warm conveyor belt;
5-10% export of NOy
mainly as PAN
PAN, weak O3
strong O3
We can explain this large OPE, looking at the GEOS-Chem model. The model predicts a region of high gross OPE over the Eastern Pacific of ~70-90 consistent with observations. This high OPE in the model is due to strong radiation over the stratus deck, and low humidity. This along with the low OH in the plume from the large HC load leading to a long NOx lifetime  large ozone enhancements.
From this we can develop a conceptual picture of ozone production. Over the continent there is ozone production with low OPE but high NOx. 5-10% export mainly as PAN. The high background of the free troposphere leads to a low delta ozone. But there is often strong subsidence around the Pacific High into a region of high OPE.
We don’t see this enhancement at the surface because of a large dilution during entrainment into the U.S. boundary layer of a factor of 10 (based on an analogy with dust data, the free tropsopheric to BL enhancement is ~ X10. For dust plumes this is huge, but for ozone, a 20 ppbv enhancement like in the May 17th plume results in only a 2 ppbv enhancement at the surface, which is undetectable.
NOx
HNO3
PAN
Asian
boundary
layer
(OPE ~ 5)
U.S.
boundary
layer
10x dilution
(Asian dust data)
very weak O3
E. Asia Pacific United States
Hudman et al. [2004]

11. MODEL vs. OBSERVATIONS AT TRINIDAD HEAD (April-May 2002)
We can see this in the surface timeseries at Chebogue point. The model is thick balck, the observed are the circles and plus signs. The MOZART model is dashed. As you can see GEOS-Chem captures the afternoon values (there is strong night depletion due to the low BL, which we would not expect to resolve. ) The dashed lines are 2 CO events, there is no corresponding ozone peak.
Observations: 38 ± 7 ppb (unfiltered)
41 ± 5 ppb (filtered against local influence)
GEOS-Chem model: 39 ± 5 ppb
MOZART model: 37 ± 9 ppb
A.H. Goldstein et al.,
J. Geophys. Res., 109,
D23S17, 2004

12. Observed 8-h ozone at Sequoia National Park (1800 m) in May 2002
CALIFORNIA MOUNTAIN SITES ARE PARTICULARLY SENSITIVE TO ASIAN OZONE POLLUTION
Observed 8-h ozone at Sequoia National Park (1800 m) in May 2002
vs. corresponding simulated (GEOS-CHEM) Asian pollution ozone enhancement
May 17 obs. Asian plume event in red
Asian enhancements are 7-10 ppbv
during NAAQS exceedances;
unlike at surface sites, Asian pollution influence is not minimum under high-ozone conditions!
California mountain sites, however, are different since they are subject to free troposphere influence. Here I show hr running mean at Sequoia National Park on the yaxis. This is a site a 1800m in south central California. On the x-axis is the GEOS-Chem simulated ozone enhancement during the same period. Hightlighted in red are the days during the pass over of the May 17th plume. On May 18th, when the May 17th plume would have moved inland to the site, the pak exceeded the U.S. air quality standard with Asian pollution contributing 7-10 ppbv according to the model. This is in contrast to surface sites which show a negative of background correlation with high ozone conditions.
Hudman et al. [2004]

13. ICARTT: COORDINATED ATMOSPHERIC CHEMISTRY CAMPAIGN OVER EASTERN NORTH AMERICA AND NORTH ATLANTIC IN SUMMER 2004
The 2nd and third parts of my thesis use observations from the ICARTT campaign, which as you know took place during the summer There were a large number of aircraft, satellitesurface components. Two major aircraft efforts were the INTEX-NA by NASA using the DC8 and ITCT 2k4 by NOAA using the WP3. The NOAA P3 stayed mostly in new england focusing on emission verification and chemical evolution of fine scale urban plumes. The NASA DC8 covered a larger region and focused on emissions and continental outflow.
SCIENTIFIC OBJECTIVES
Regional Air Quality
Continental Outflow
Transatlantic Pollution
Aerosol Radiative Forcing

14. Biomass burning 2004 Persistent Alaskan and Canadian burning
CO June – August 2004
Canada
Canadian National Forest Fire Situation Report Sept 8, 2004 (
2004 was a very large fire year as you measured on Cobra over Alaska and Canada. It was the largest fire season in Alaska and here I am showing Canada hectares burned and you can see it is well above the 10 year avg. Solene Turquety in are group created a biomass burning inventory based on MODIS hotspots and area burnded…simulated results are shown here and were validated using the MOPITT instrument.
Wildfires in Alaska: > 2,500,000 Hectares!
Alaska Fire services: “The largest fire season in Alaska’s rich history ”
Biomass burning inventory created using MODIS hotspots and daily area burned
[Turquety et al., 2007]

15. Lightning X4 over U.S. & distributed to tropopause
Flash counts (flashes/km2/s)
GEOS-CHEM SIMULATION
Modifications from ICARTT constraints in blue (improved)
NOx Lightning Emissions
Lightning X4 over U.S. & distributed to tropopause
[Price and Rind, 1992]
We again use GEOS-Chem. Of special importance to this study - NOx lightning emissions are following the cloud top height raised to the fifth power of Price and Rind, scaled to match tropical ozone concentrations yielding 4.7 tg N/year. We use the NEI99 v1 EPA inventory over the U.S. with modifications to some VOCs based on past budget analysis. Due to the large fire year, we use a May-August 2004 fire inventory for North America developed by Solene Turquety.This model has been extensively tested and includes the latest findings in the description of the Noy budget over N. America as we presently understand it.
NOx emission
CO emissions
EPA National Emissions Inventory 1999 v1 (w/ modifications to VOCs)
Power plant and Industry NOx %
Anthropogenic CO 60%
May-August 2004 NA Fire Inventory
[Turquety et. al, 2007]

16. GEOS-CHEM VS. ICARTT Mean comparison along the flight tracks
Ozone FT bias 5-10 ppbv
Large UT NOx bias
BL bias in CO and NOx
Using this simulation GEOS-Chem simulation sampled along the NASA DC-8 and NOAA WP3 flight tracks, we found some discrepancies in our current understanding of the North American NOy budget, particularly in upper tropospheric NOx and ozone concentration as well as in changes in emissions over the U.S. since Shown here in red are mean simulated profiles using our standard simulation. The black are mean observations. The WP3 and DC-8, shows a CO bias in the lowest two km, which Lee Murray discussed in his presentation yesterday. For NOx we also see a model high bias in the lowest two km. Striking are two features in the upper troposphere…elevated NOx underestimated in the model by a factor of 4 with current emissions estimates and a 5-10 ppbv bias in oxone throughout the free tropospheric over the U.S. with current emissions.
Measurements (WP-3D, DC-8): CO (J. Holloway, G. Sachse), NOx (T. Ryerson, R. Cohen, W. Brune), PAN (F. Flocke, H. Singh), HNO3 (A. Neuman, J. Dibb), ozone (T. Ryerson, M. Avery)

17. ICARTT OBSERVATIONS CONFIRM LARGE DECREASE SINCE 1999 IN INDUSTRY/POWER SOURCE
Large overestimate powerplant/industry dominated Midwest and in the South
Model / Observed NOx (0-2 km)
DC-8 Midwest
Observed Simulated Improved Simulation
[ratio]
The NOx bias can be explained by a decrease in the powerplant/industry source by 50% between as a result of the NOx SIP. This is evident in the Model/Observation ratio map. The largest discrepancy is over the midwest and in other powerplant dense regions. We reduced the powerplant/industry emission by 50% , greatly improving the NOx simulation at the surface.
50% reduction in power and industry source as determined by Frost et al., [2006] improves boundary layer NO2 simulation
Hudman et al. [2006a,b]
Measurements (WP-3D, DC-8): T. Ryerson (NO2), Ron Cohen/Tim Bertram (NO2)

18. MEAN AFTERNOON OZONE CONCENTRATIONS 0-1.5 KM DURING ICARTT
SIMULATED (NEI99 stationary NOx source reduced by 50%)
OBSERVED
SIMULATED (NEI99)
This figure shows observed and simulated mean km afternoon ozone concentrations during ICARTT. Cool temperatures, cloudiness, and frequent frontal passages made summer 2004 a mild ozone season. Mean observed concentrations were typically ppbv. High values observed offshore reflect aged urban pollution plumes deliberately sampled by the WP-3D aircraft in stratified air and should not be viewed as representative. The simulation using NEI 99 is too high over the United States by 5-15 ppbv, with a simulated-to-observed regression slope of 1.05 ± 0.10 (R2 = 0.30). he NOx reduction improves the ozone simulation in the South and Midwest, though it only slightly improves the overall model-to-observed ozone correlation (0.95 ± 0.07, R2 = 0.34).
Stratified local plumes, not representative
High bias in the South and Midwest improved
simulated-to-observed regression slope (afternoon, overland, 0-1.5km):
NEI 99: 1.05 ± 0.10 (R2 = 0.30); NEI 99 Reduced NOx: (0.95 ± 0.07, R2 = 0.34).
Measurements (WP-3D, DC-8): T. Ryerson, M. Avery

19. OZONE REDUCTIONS RESULTING FROM DECREASE IN NOx EMISSIONS
Regional differences in ozone, can be explained by OPE:
OPE
Midwest:
Southeast:
The NOx emission reductions are largest in the Midwest, reflecting the distribution of power plants. The largest resulting ozone decreases in the model are in the southeast, the midwest shows weaker decreases 4-6 ppbv. These spatial differences in the different responses to ozone can be explained by regional variations in OPE. OPE decreases with increasing NOx and increases with increasing isoprene and UV flux. The Midwest BL OPE is where as the Southeast is 4-5.5, consistent with simulated ozone decreases.
We next wanted to see how changes in OPE and NOx have led to changes in observed o3/co correlations, an in turn NA export. Observed O3/CO can be approximated as OPE * ENOX/ECO. But this requires a good CO source.
Can we see changes in OPE due NOx emission reductions in dO3/dCO in U.S. outflow?
Requires good estimate of CO source…..

20. J. Holloway, G. Sachse, A. Goldstein
BOTH AIRCRAFT AND SURFACE DATA SUGGEST NEI 99 CO EMISSIONS ARE 2.5 TIMES TOO HIGH
Measurments:
J. Holloway, G. Sachse, A. Goldstein
SIMULATED (anthro CO reduced by 60%)
SIMULATED (NEI99)
OBSERVED
Measurments:
J. Holloway, G. Sachse
Aircraft (0-1.5 km)
The top figure compares simulated and observed mean CO concentrations in the boundary layer during ICARTT. The model using NEI-99 shows a consistent overestimate of ppbv that matches the spatial distribution of the anthro CO source. Surface observations at Chebogue Point show a similar overestimate.
Measurments:
A. Goldstein
Chebogue Point (surface)

21. CO OVERESTIMATE IS NOT CAUSED BY INSUFFICIENT VENTILATION OR BIOGENIC SOURCE
Boundary layer ventilation is constrained by vertical profile of short-lived VOCs
Biogenic VOCs are well-constrained by successful simulation of formaldehyde
This overestimate could reflect either excessive source, insufficient ventilation. On the left I show a profile of propane a moderately short lived species (~3 days) with only a surface source. We can test convection by looking at the observed profile shape. We see the model matches the shape of this and other NMVOCs during ICARTT. This overestimate doesn’t seem to be in anthropogenic VOCs since propane and other species (which?) are well simulated.
Propane: E. Atlas CH2O: Alan Fried

22. SCATTERPLOT OF SIMULATED TO OBSERVED CO
Parrish [2006] finds on-road source overestimated by 50% in NEI 99 (~33% reduction in NEI source)
CO decrease trend 3.7% yr-1 ( ), (12% reduction in NEI source since 1999)
 This estimate 2004 emissions 45% lower than NEI 99

23. ANTHROPOGENIC CO SOURCE IN THE UNITED STATES IN SUMMER IS NOW LOWER THAN BIOGENIC SOURCE
NEI 99
NEI 99 with 60% reduction in CO
Here I am showing pie charts of the fraction of CO from different sources. We get the isporene and biogenic sources of CO assuming CO yields based on. This is likely an overestimate because it does not account for deposition and assumes all the isoprene goes through HCHO --> CO. In the model these are calculated online.
After reducing the Anthropogenic CO source by 60%, anthropogenic CO accounts for 30% Anthropogenic VOCs an additonal 11% making the anthropogenic contribution 41%. Biogenic emissions contribute 58%with the largest source from isoprene making biogenic CO dominate over anthropogenic CO in the summer.
SOURCE TYPE (Tg CO)
CO ANTHROPOGENIC EMISSION (11.5, 4.6)
CO SOURCE FROM ANTHROPOGENIC VOC OXIDATION (1.8, 1.8)
CO SOURCE FROM ISOPRENE OXIDATION (6.7, 6.7)
CO SOURCE FROM OTHER BIOGENIC OXIDATION (2.4, 2.4)
CO SOURCE FROM OTHER BIOMASS BURNING OVER CONTINENTAL U.S.(0.16, 0.16)  Note: Fires in Canada and Alaska ~19 Tg CO

24. OZONE-CO CORRELATIONS SHOW DECADAL INCREASE
Aircraft (0-1.5 km, 11-5pm LT)
Chebogue Point
ALL WIND DIRECTIONS
WINDS FROM W-SE
Overestimate of tropical background
Here I am showing ozone/CO correlations from the DC-8 aircraft and the Chebogue Point surface site on the southern tip of nova ScotiaThe Aircraft data are from 11 am – 5pm, excluding fresh plumes. For chebogue point we show data from the W-SE which sampled NA outflow. ThedO3/dCO in the obse is 0.47 (R2=0.54) and the corresponding model ratio is 0.36 (R2-0.21). This is caused by an overestimate of the ozone background in the Southeast and tropical airmasses. Looking at the regions geographically, we found what really dominates this slope is emission from the NE U.S.
The slope at Chebogue Point is lower 0.4, consistent although slightly lower than observations. The same problem exists with background as above. Previous studies found slopes of The higher values could be due to decadal changes in U.S. CO and NOx emissions.
Obs during the early 90s show dO3/dCO ~ 0.3 – 0.4 [Chin et al., 1994; Parrish et al., 1998].
Change could be due to decadal changes in emissions

25. OBSERVED dO3/dCO INCREASE OVER THE PAST DECADE CONSISTENT WITH UNDERSTANDING OF OPE AND SOURCES
dO3/dCO  OPE (dO3/dNOx) * NOx/CO source ratio (dNOx/dCO)
Consider NE U.S.,
July 1 – August 15, (With ICARTT Constraints)
Anthro = 1.2 Tg CO, 0.10 Tg N Biogenic = 0.87 Tg CO
July 1 – August 1994
4.9% anthro decrease/year in urban air [Parrish, 2006]  Total CO 26% higher
22% stationary NOx reduction [Hudman et al., 2007]  Anthro NOx 15% higher
 OPE lower by ~9%
 NOx/CO source ratio lower by ~19%
If we look at dO3/dCO it is ~ OPE * NOx/ CO source ratio. If we consider the NE U.S. where the emissions are predominantly vehicular. We can use the 4.9% decrease yr-1 deduced by Parrish. That is a 26% decrease in the last 10 years in total CO. As I showed earlier there was 22% reduction in NOx since 1999, before then NOx was relatively stable. In the NE this is 15% greater. This change is a 9% change in net OPE, and a 19% change in NOx/CO. So from this we would expect a 28% increase in dO3/dCo, which is what we see. The ozone flux calculated is consistent with 1990s estimates (which had low CO emissions).
~28% increase in dO3/dCO expected (90s)  (present)
Multiply dO3/dCO * ECO 1.5 Gmol ozone d-1 (Ozone flux consistent with 1990s estimates)

26. SPECIATION AND EXPORT OF BOUNDARY LAYER NOx
Onshore %
Offshore %
OBSERVED
GEOS-Chem
Model successfully simulates boundary layer NOy
NOx
We find observed f = 16  10% and modeled f = 14  9% ( km)
18% 7%
PAN
f= export efficiency
R = ECOanthro/ENOxanthro
 = NMVOC CO production
20% 9%
NOy speciation is well simulated by the model. Here I am showing HNO3 + PAN + NOx fractions of total NOy. Because we are interested in export, we assume these are all of the NOy. ANs are less than 3% in the free troposphere, as are higher PANs, and nitrate aerosol. We see NOx/NOy is 18% over the continent and 7% off shore, HNO3 is dominant component everywhere with 62% on land an 84% off shore. PAN is favored in the south because of isoprene.
We can develop a simple observationally based diagnostic of export, by defining an export efficiency or fraction of NOy by viewing CO as an inert tracer of anthropogenic emissions. So R is the anthroponic CO/NOx emissions ratio. Alphs is the oxidation of VOC CO source From this we calculate and export fractuib if 16 +/- 10 in the observations and 14 +/0 9 in the model. The components of this esport are mostly HNO3 just above the boundary layer due to dry bl venting. And mostly PAN above 4km supporting global estimates of a large PAN contribution to hemispheric ozone.
HNO3
Export to the lower free troposphere is mostly HNO3 but at higher altitudes is mostly PAN.
62%
84%
Hudman et al. [2007a]

27. UT NOx OBSERVATIONS POINT TO A LARGER THAN EXPECTED LIGHTNING NOx SOURCE
NOx (8-12 km)
Observed
GEOS-Chem (Lightning X4)
[ppbv]
Here I am showing Observed NOx between 8-12 km. We saw very large values of NOx between ppbv all the time. We argue that this is a lightning source. The aircraft source is well constrained, and convection doesn’t show a bias for bl species like propane. This doesn’t appear to be a NOx lifetime issue because if it were, we would expect when looking at a frequency distribution of NOx to see more variability in the model than in the observations. This isnt the case adding some support to the argument that OH is ok.
DOESN’T APPEAR TO BE A NOx LIFETIME ISSUE
Hudman et al. [2007a]
NO: W. Brune, NO2: R. Cohen/T Bertram

28. FLASH RATES WELL SIMULATED POINTING TO A LARGER YIELD/FLASH AT NORTHERN MIDLATITUDES
Lightning parameterization (flashes/km2/s):
Land : ~CTH4.9 , Ocean: ~CTH1.73
CTH= Cloud Top Height
Price and Rind [1992]
Flash Comparison
GEOS-Chem
GEOS-Chem Vertical Distribution
Pickering et al., [1998]
[Flashes km2 s]
NLDN
The way that we parameterize lightning in the model is using the CTH scheme, this scheme is based on observations that flash frequency is related to CTH, additionally its related to updraft velocities. The velocities are lower over the ocean and by the ratio of land/ocean updraft Price and Rind came up with the ocean parameterization. Here I am showing a comparison of NLDN flashes vs. GEOS-Chem over the U.S. What we see in NLDN is largest flash counts over the Gulf and up the Ohio River Valley and over monsoonal southweat. The model captures the high frequency over the Gulf but does not capture the northerly extent. So at leaast over the South we need to increase the NOx yield /flash

29. PEAK CURRENT AS A FUNCTION OF LATITUDE
One way Nox emissions are calculated is using the peak current (or energy of the storm). The higher the energy the higher the yield. Here Heidi Huntrieser in Germany found midlatitude peak currents are higher than tropical storms. Its unclear why but may be do to aerosol charging increasing the charge separation.
[Huntrieser et al., 2005]

30. NO PRODUCTION RATE CALCULATED FROMR RECENT CAMPAIGNS
Over midlatitudes Ken Pickering shows a distribution flash production vs. IC/CG ratio of storms. The green and red are over the U.S. The blue are over Europe. The black like is the US. Median when using flash counts from NLDN. They predict 500 mol/flash. GEOS-Chem predicts ~125 mol/flash worldwide over the continents. So we increase this by a factor of 4.
Standard GEOS-Chem mean flash rate was 125 mol flash-1 (Improved  X4  500 mol flash-1)
[Ken Pickering]

31. OZONE COMPARISON INTEX-NA SOUTHEAST U. S
OZONE COMPARISON INTEX-NA SOUTHEAST U.S Increase in lightning yield X4 to 500 mol/flash has ~10 ppbv effect on ozone O3
NO2
2004 was not an anomalous lightning year
Observed Simulated Improved Simulation
When we do this. We find in th esouth NOx is completely corrected and it also corrects a 5-10 ppbv bias in ozoen throught the free troposphere. This suggests a great sensitivity to lightning changes under a warming cliimate wasn’t an anomolous year. Here I am showing GEOS-Chem flashes over the U.S. and coastal waters and NLDN. The jump in is due to upgarades completed late so the comparable years are In both the model and NLDN there is not much interannual variabillty.
Hudman et al. [2007a]
…suggests great sensitivity of ozone to climate change

32. SUMMERTIME NORTH AMERICAN OZONE ENHANCEMENTS
ICARTT DC-8
~ Equal contributions for lightning and anthropogenic emissions in free troposphere and to NH burden
NA Enhancement to Hemispheric Ozone
North American Source
NOx Emission (Tg N)
Ozone Production Efficiency
Hemispheric ozone enhancement (Tg, %)
Lightning
0.28
32.5
9.1 (5.1%)
Biomass burning
0.32
17.5
5.6 (3.1%)
Fossil fuel
0.72 15
10.9 (6.1 %)
All
1.32 19
25.6 (14.3 %)
The ICARTT campaign offered cpmstraints on NOx emissions from anthropogenic emissions, lightning and biomass burning and implied large corrections for these. we developed a new estimate for North American contribution to hemispheric ozone.
Here I am showing enhancements from these individual sources along the DC-8 flgiht tracks. The total North American enhancements amounts to 30 ppbv in the bioundary layer and 20 ppbv in the free troposphere. BL is mainly anthropogenic but in the free troposphere there are equal enhancements from lightning and anthropogenic emissions. Biomass added 2-4 ppbv to 4km and less above.
Hudman et al. [2007b]
Biomass Lightning Anthropogenic
Simulated Observed All

33. NORTH AMERICAN ENHANCEMENT TO HEMISPHERIC OZONE
Here I am showing ozone enhancements from different North American NOx sources at different altitudes. Qinbin Li found a permanent upper level cyclone along the southern U.S. allowing ozone buildup. Cooper found and associated ppbv from ightning. We find a similat ppbv stretching woenwind across subtropical Atlantic to Europe.
Th emean NA anthro enhancement is at the surface but shifts NE in the Atlantic free troposphere reflecting frontal passages. NA emissions extend further north than lightning.
Biomass burning is highest in boreal regions reflecting the high fire ywar. Emissions extend to the Arctic where they dominate over anthro, lightning at the surface but not in the upper troposphere. Enhancements of 3-5 ppbv are seen over Western Europe similar to anthropogenic emissions.
Hudman et al. [2007b]

34. Anthropogenic CO emission in NEI 99 is overestimated by 60%.
MAJOR FINDINGS (1)
PAN decomposition represents a major and possibly dominant component of the ozone enhancement in transpacific Asian pollution plumes.
A factor of 10 dilution of Asian pollution plumes takes place during entrainment in the U.S. boundary layer, greatly reducing their impact at U.S. surface sites.
California mountain sites are more sensitive to Asian pollution because of their exposure to the free troposphere. Asian enhancements are 7-10 ppbv during NAAQS exceedances; unlike at surface sites, Asian pollution influence is not minimum under high-ozone conditions.
A 50% summertime powerplant/industry NOx reduction source 1999 results in an 4 – 8 ppbv reduction in ozone at the surface with maximum effect in the southeast.
Anthropogenic CO emission in NEI 99 is overestimated by 60%.
The biogenic CO source now exceeds the anthropogenic source in summer.
Replace ‘strong dilution’ by ‘factor of 10 dilution’
I think an important result about the CA mountain sites is that the model attributes 6-8 ppb to Asia under conditions where the NAAQS is exceeded.
Finding 3 should partly be about confirming the NOx decrease. Replace “varying due…” by “with maximum effect in the southeast’. You can then comment orally on how that reflects the higher OPE there.
Finding 4: Anthropogenic CO EMISSION … point out orally that this implies large overestimate of off-road sources, which people hadnt looked at previously. Write down as major finding that the biogenic CO source now exceeds the anthropogenic source in summer – it IS a major finding. So much for CO providing a tracer of pollution!
Finding 6 is grammatically challenged. Fix.
Finding 7: give numbers, conclude as to trend in ozone export.
Finding 8: should really be split into two or more findings about (1) relative contributions of anthro, bb, and lighting; (2) % N American contribution to NH budget; (3) bb vs. anthro surface influence over Europe.
Nothing wrong with presenting the major findings over two slides, ‘Major findings (1)’ and ‘Major findings (2)’

35. MAJOR FINDINGS (2)
7. dO3/dCO in NA boundary layer outflow is ~28% higher than in the early 1990s, consistent withour understanding of changes in OPE and emissions.
8. Lightning is the dominant source of UT NOx over United States during the summer and had ~10 ppbv impact on upper tropospheric ozone.
9. Successful simulation of lightning over the U.S. requires a factor of 4 increase in NOx yield to 500 mol flash-1.
10. Lightning & Anthropogenic emissions each enhance ozone by ppbv in the upper free troposphere over the U.S. Biomass burning enhancement over the Eastern U.S. was greatest below 4 km (~3-4 ppbv).
11. Lightning & anthropogenic emissions have a roughly equal enhancement to hemispheric ozone (~5%) during the summer.
12. Biomass burning emissions enhance surface ozone over Western Europe by 3-5 ppbv, comparable to the enhancement from fossil fuel.
Conclusions Slide 19 of 19