Tropospheric ozone and its precursors over the United States:

Sources and intercontinental influence

Rynda Hudman Postdoctoral Fellow

University of California, Berkeley

Lawrence Livermore National Lab June 17, 2010

CONTINENT 2 OCEANCONTINENT 1

INTERCONTINENTAL INFLUENCE OF OZONE (1) primary constituent of smog in surface air [NRC, 1991]

(2) 3rd most important greenhouse gas [IPCC, 2007]

OH HO2

CO, VOCs

NONO2

h

Hemispheric Pollution

Direct Intercontinental Transport(1 week)

Air quality

Greenhouse gas

4

8

2

Alt (km)

10

6

Air quality

O3= NOx

NOx HAS OTHER WIDESPREAD CONSEQUENCES

NO

NO2 HNO3

• Acidification of soils and waterways

• Eutrophication of waterways

• Forest die-back

• impacts carbon sequestration

• Secondary organic aerosol formation

• Impacts GHG lifetimes through its effect on OH

hrs - 1 day

SOURCES OF NOx

Fossil Fuel

ANTHROPOGENIC SOURCESBIOGENIC SOURCES

FF: 21-28 TgN/yrBB: 6-12 Tg N/yr

Lightning: 1-6 TgN/yr

*Numbers from IPCC [2007]

Biomass Burning

Natural Soils: 5-8 TgN/yr

Agr: 0.5-2 TgN/yr

• Can we better constrain the magnitude of these sources?

• Can we go beyond previous work and understand the physical processes governing biogenic sources?

AgricultureNatural Soils

OUTLINE

Do we understand nitrogen transformations in the atmosphere?

Can we constrain magnitude and processes governing N sources over North America?

•Anthropogenic •Lightning•Soils•Biomass Burning

What are the impacts on hemispheric ozone and air quality?

UNITED STATES OCEANASIA

SOURCES

1. TRANSPACIFIC TRANSPORT OF ASIAN POLLUTION AND IMPACT ON U.S. AIR QUALITY

CHEMICAL EVOLUTION AIR QUALITY IMPACTS

NO

NO2 HNO3 (soluble)

PAN (insoluble, thermally unstable)

NOy

NOAA ITCT-2k2: APRIL – MAY 2002Monterey, CA

Flight path: Sampled several Asian pollution plumes

May 5th

May 17th

5-7 km

High CO

Moderate Ozone

2-4 km

High CO

High Ozone

Primarily Anthropogenic, but very different pathways

Hudman et al., [2004]

TWO FOSSIL FUEL POLLUTION PLUMES OF ASIAN ORIGIN

High PAN

PAN NOx HNO3

LARGE PAN DRIVEN OZONE PRODUCTION

Observational Estimate:

17 ppbv ozone produced from 320 pptv PAN

Ozone production per unit NOx ~ 50

~50% of ozone produced from PAN decomposition

Hudman et al., [2004]

PAN DRIVEN OZONE PRODUCTION IN SUBSIDING TROPOSPHERIC POLLUTION PLUMES

Observations: 38 ± 7 ppb (unfiltered), GEOS-Chem model: 39 ± 5 ppb 41 ± 5 ppb (filtered against local influence)

[Goldstein et al.,2004]

Model vs observations at Trinidad Head (April – May 2002)

WHY WERE NO PLUMES SEEN AT THE SURFACE?

Analogy to dust: X10 dilution as plume entrained to boundary layer 20 ppbv ozone enhancement 2 ppbv enhancement at the surface

Likely very different at mountain sites, due to greater exposure to FT!

OCEAN

2. CONSTRAINING ANTHROPOGENIC SOURCES OF NOx

GEOS-CHEM SIMULATION• Lightning, Soils

• NEI 99 FF Emiss

•Daily biomass burning inventory

ICARTT Campaign

July-August 2004

Full mapping of Eastern U.S. and North Atlantic

LARGE DISCREPENCY IN SURFACE NOx and CO Mean comparison along the flight tracks

Measurements: CO (J. Holloway), NOx (T. Ryerson)Hudman et al. [2007]

BL bias in CO and NOx

Observed Simulated Improved Simulation

DC-8 Midwest

Model / Observed NOx (0-2 km)

Hudman et al. [2007]

[ratio]

Large overestimate powerplant/industry dominated Midwest and in the South

50% reduction in power and industry source due to SIP Call [Frost et al., 2006]

ICARTT OBSERVATIONS CONFIRM LARGE DECREASE SINCE 1999 IN INDUSTRY/POWER SOURCE

Measurements (WP-3D, DC-8): T. Ryerson (NO2), Ron Cohen/Tim Bertram (NO2)

Measurments: J. Holloway, G. Sachse, A. Goldstein

BOTH AIRCRAFT AND SURFACE DATA CO EMISSIONS ARE 2.5 TIMES TOO HIGHERROR IN OTHER SPECIES

Air

craf

t (0

-1.5

km

) OBSERVED SIMULATED (NEI99) SIMULATED (anthro CO reduced by 60%)

Measurments:

J. Holloway, G. Sachse

Ch

ebo

gu

e P

oin

t (s

urf

ace)

Measurments: A. Goldstein

Hudman et al. [2008]

OZONE REDUCTIONS RESULTING FROM DECREASE IN NOx EMISSIONS

Hudman et al. [2009]Bias reduces previous model of 5- 15 ppbv

3. LIGHTNING SOURCES OF NOx

Large UT NOx bias

Ozone FT bias 5-10 ppbv

Hudman et al. [2007]NO: W. Brune, NO2: R. Cohen/T Bertram

UT NOx (8 – 12 km)

GEOS-Chem X4 DC-8

UT NOx OBSERVATIONS POINT TO A LARGER THAN EXPECTED LIGHTNING NOx SOURCE

[ppbv]

Lightning parameterization in model (flashes/km2/s):

Land: ~CTH4.9 ,

Ocean: ~CTH1.73

CTH= Cloud Top Height

Price and Rind [1992]

FLASH RATES WELL SIMULATED IN SOUTH POINTING TO A LARGER YIELD/FLASH AT NORTHERN MIDLATITUDES

GEOS-Chem

NLDN

Flash Comparison (flashes/km2/s)

0.22 0.33

OZONE COMPARISON INTEX-NA SOUTHEAST U.S. Increasing lightning yield X4 to 500 mol/flash has ~10 ppbv effect on

ozone

NO2O3

Hudman et al. [2007]…suggests great sensitivity of ozone to climate change

Observed Simulated Improved Simulation

2004 was not an anomalous lightning year

Hudman et al. [2009]

SUMMERTIME NORTH AMERICAN OZONE ENHANCEMENTS

Biomass Lightning Anthropogenic

Simulated Observed All

North American

Source

NOx

Emission (Tg N)

Hemispheric ozone

enhancement (Tg, %)

Lightning 0.28 9.1 (5.1%)

Biomass burning

0.322.0(1.1%)

Fossil fuel 0.72 10.9 (6.2 %)

All 1.32 21.9 (12.3 %)

NA Enhancement to Hemispheric Ozone

ICARTT DC-8~ Equal contributions for lightning and anthropogenic emissions in free troposphere and to NH burden

Can use to develop radiative forcing estimates

North America

Subsidence Over E Pacific

PANNOxHNO3

strong O3

X10 Dilution

Asian Plume

Asia

Europe

INFLOW

KEY RESULTS

NOx stationary sources 22%

Anthropogenic CO 60%

4

2

6

8

Alt (km)

10

O3 (ppbv)

SOURCES AND EXPORT

BB NA FF Lightning

NOx/flash4X larger than previously thought!

Export well constrained

effects on O3 & OPE

SUMMERSPRING

3. SPACE BASED CONSTRAINTS ON SOIL NOx

Most of what we know about processes responsible for soil NOx emissions is based on point measurements.

ATMOSPHERE

BIOSPHERE

NO is a low-yield product of nitrifying bacteria

N2O(g), N2(g), NO(g)

[Meixner and Yang, 2006]

Processes not well understood, HUGE spatial variability, but best correlation soil moisture (precip), T, N avail.

WHERE TO EXPECT LARGE NITRIC OXIDE EMISSIONS: Fertilized fields and monsoon regions

Pulsing : Release of soil NO following rain event, due N-buildup & reactivation of water-stressed bacteria

• Monsoon:

1. SW U.S./Mexico

2. Africa/ITCZ

3. Southeast Asia

• Fertilized Fields:

1. United States

2. Europe

LARGE SOIL NOx SOURCE INFERRED FROM SATELLITES

Regional Distribution of soil NOx

[Jaeglé et al., PNAS, 2005]

GLOBAL: 8.9 Tg N/yrMIDLATITUDES: 3.9 Tg N/yr

We examine interannual variability in soil NO emissions and our understanding of pulsing behavior over the Agricultural Great Plains

OMI NO2 Column Aug 4, 2004

• 2600 km swath width providing daily global coverage

•1:45 pm equatorial overpass time

•14 x 24 km pixel size at nadir

OZONE MONITORING INSTRUMENT (OMI) HAS MUCH FINER SCALE RESOLUTION AND DAILY GLOBAL COVERAGE

[Bertram et al., GRL, 2005]

SOIL NOx “EVENTS” pulsing over freshly fertilized Montana fields after rain event

[Bertram et al., GRL, 2005]

We extend this work to include U.S.:daily NARR Temp & Precip MODIS LandtypeFertilizer emissions [Ramankutty]

ENOx 2005-2008

Hudman et al. [2010]

CAN SOIL NOx EMISSIONS BE ROUTINELY VIEWED FROM SPACE?

MODELED SOIL NOx EMISSIONS Dry, warm conditions anomalously high modeled June 2006 soil emissions

Hudman et al. [2010]

SOIL EMISSION CONTRIBUTION TO NO2 COLUMN

June 2006

SOIL COLUMN / TOTAL COLUMN SOIL S.D. / COLUMN S.D.

SOIL COLUMN = TOTAL COLUMN – NO SOIL COLUMN

GEOS-Chem global CTM (2x2.5)

Hudman et al. [2010]

We should be able to see anomalies in soil NOx and day-to-day variability over Great Plains

OMI NO2 JUNE INTERANNUAL VARIABILITY FOLLOWS PREDICTED SOIL NOx

OMI June 2006 AnomalySoil NO model June 2006

June 2006 had lower than average lightning emissions, suggesting this was not a factor here

Hudman et al. [2010]

OMI NO2 JUNE INTERANNUAL VARIABILITY FOLLOWS SOIL NOx

2005 20072006

Hudman et al. [2010]

Suggests fertilizer induced emissions of soil NOx governs monthly variability in NO2 column over Great Plains… what about pulsing?

PULSING OVER EASTERN SOUTH DAKOTA

Pulsing event reaches 4x1015 molec cm2,

~ 2 ppbv assuming 1km well mixed BL

Hudman et al. [2010]

We can use OMI to test understanding pulsing triggers

North America Asia

Europe

KEY RESULTS

• Space-based observations can offer constraints on soil NOx

•Large scale behavior consistent with models.

•Observed interannual anomaly is similar to model predictions.

•Mechanistic details of pulses bear some resemblance, learning about the process of soil NOx emissions remains a challenge.

•Because large scale features are well represented ozone air quality

MEAN MAXIMUM 8-HR OZONE ENHANCEMENT DUE TO SOIL NOx

Ozone enhancement due to soil NOx emission doubles from 3 6ppbv, with events up to 16 ppbv!

Comparable to decreases from power plant legislation discussed earlier.

Hudman et al. [2010]

Hudman et al. , in prep.

4. BIOMASS BURNING & CLIMATE

North America

•What is the relationship between Area Burned and Meteorology/Moisture?

• We can drive these relationships into the future using GCM Future Area Burned

• Develop future ozone and aerosol precursor emission estimates

•Chemical transport model (driven by GCM winds) impacts on air quality

During ICARTT, we were able to put some estimates on NOx

emissions from fires…here we want to look at processes….

CANADIAN FIRE WEATHER INDEX MODEL

2/3 day 15 day 52 dayDrying time

Severity Rating

WEATHER

MOISTURE

FIRE DANGER

Jul 1 – Aug 15 2004 Anomaly

Strong Alaskan Ridge record fires

+60

500hPa GEOPOTENTIAL HEIGHT

Height of pressure level above mean sea level

Strong ridges are accompanied by warm and dry weather conditions at the sfc

(Hudman et al., in prep)

Regressions capture 74% of the variability in Canada and Alaska

Major predictors: 500 mb GPH (large scale stagnation) and drought indices

Hudman et al. , in prep.

REGRESSIONS CAPTURE VARIABILITY OF AREA BURNED

34% increase over Alaska, 8% (-34 to +118%) increase in Canada. Large regional variability.

2000-2050 change in area burned

RAIN VS. STAGNATION UNCERTAINTY IN RESPONSE

++ Rain500 GPH changes

Hudman et al., in prep

(Hudman et al., in prep)

CHANGE IN SURFACE OZONE ENHANCMENT JUL-AUG

Doubling of enhancement over Alaska, 1-2ppbv increase over populated Quebec cities and Midwest (20-40% increase)

A decrease of ozone toward the Arctic

PERCENT CHANGE IN SURFACE OC/EC JUL-AUG Preliminary Result

(Hudman et al., in prep)

[%]

Transport of Black Carbon aerosol to the Arctic decreases by 40%

KEY RESULTS

500 mb GPH anomaly & fuel moisture are most important variables

Large regional variability in the response, due to dependence on rainfall vs. stagnation (highly GCM dependent).

Present day ozone enhancements due to wildfire 3-10 ppbv over Canada and Alaska. Future fire increases range from -2 - +4 ppbv. Large decreases of BC toward the Arctic.

North America

WHAT HAVE WE LEARNED? FUTURE DIRECTIONS?

1. TRANSFORMATION: PAN decomposition represents a major and possibly dominant component of the ozone enhancement in transpacific Asian pollution plumes. Dilution limits surface impacts.

2. ANTHROPOGENIC: NOx reduction legislation has been successful 4-8 ppbv decrease in summertime ozone.

3. CO emissions are overestimated in current inventories impacts on other species estimates such as CO2

4. LIGHTNING: Lightning at midlatitudes produces X4 more NOx/flash than midlatitude/subtropical storms 10-15 ppbv ozone, comparable to anthropogenic emissions

5. SOIL: Soil NOx emissions are highly dependent on temperature and precipitation, impacts on ozone ~6 ppbv (events reaching 16 ppbv), comparable to #2 above.

6. BIOMASS BURNING: Future fire activity likely depends on fuel moisture and atmospheric stability, both of which are highly variable in GCM projections.

ACKNOWLEDGEMENTS

Thanks for your attention!

Advisors: Ron Cohen, Daniel Jacob, Jennifer Logan, Loretta Mickley, Students and postdocs: Lee Murray, Dominick Spracklen, Ashley Russell, Luke Valin, Solene Turquety, Shiliang Wu, Dylan Millet, Agency: Mike Flannigan (CFS), Alan Cantin (CFS), Alice Gilliland (EPA)

FUNDING: EPA, NASA, NOAA, NSF PhD Fellowship, AMS Graduate Fellowship

ITCT-2K2 & ICARTT, Science TeamsAURA Science Team