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 OCEAN CONTINENT 1 INTERCONTINENTAL INFLUENCE OF OZONE (1) primary constituent of smog in surface air [NRC, 1991] (2) 3 rd most important greenhouse gas [IPCC, 2007] OHHO 2 CO, VOCs NO NO 2 h Hemispheric Pollution Direct Intercontinental Transport (1 week) Air quality Greenhouse gas Alt (km) 10 6 Air quality O3O3 = NO x

NOx HAS OTHER WIDESPREAD CONSEQUENCES NO NO 2 HNO 3 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 NO x Fossil Fuel ANTHROPOGENIC SOURCESBIOGENIC SOURCES FF: TgN/yr BB: 6-12 Tg N/yr Lightning: 1-6 TgN/yr *Numbers from IPCC [2007] Biomass Burning Natural Soils: 5-8 TgN/yr Agr: 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? Agriculture Natural 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 OCEAN ASIA SOURCES 1. TRANSPACIFIC TRANSPORT OF ASIAN POLLUTION AND IMPACT ON U.S. AIR QUALITY CHEMICAL EVOLUTION AIR QUALITY IMPACTS NO NO 2 HNO 3 (soluble) PAN (insoluble, thermally unstable) NO y

NOAA ITCT-2k2: APRIL – MAY 2002 Monterey, 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  HNO 3

LARGE PAN DRIVEN OZONE PRODUCTION Observational Estimate: 17 ppbv ozone produced from 320 pptv PAN Ozone production per unit NO x ~ 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), NO x (T. Ryerson) Hudman et al. [2007] BL bias in CO and NO x

Observed Simulated Improved Simulation DC-8 Midwest Model / Observed NO x (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 (NO 2 ), Ron Cohen/Tim Bertram (NO 2 )

Measurments: J. Holloway, G. Sachse, A. Goldstein BOTH AIRCRAFT AND SURFACE DATA CO EMISSIONS ARE 2.5 TIMES TOO HIGH  ERROR IN OTHER SPECIES Aircraft (0-1.5 km) OBSERVED SIMULATED (NEI99 ) SIMULATED (anthro CO reduced by 60%) Measurments: J. Holloway, G. Sachse Chebogue Point (surface) Measurments: A. Goldstein Hudman et al. [2008]

OZONE REDUCTIONS RESULTING FROM DECREASE IN NO x EMISSIONS Hudman et al. [2009] Bias reduces previous model of ppbv

3. LIGHTNING SOURCES OF NOx Large UT NO x bias Ozone FT bias 5-10 ppbv

Hudman et al. [2007] NO: W. Brune, NO 2 : R. Cohen/T Bertram UT NOx (8 – 12 km) GEOS-Chem X4 DC-8 UT NO x OBSERVATIONS POINT TO A LARGER THAN EXPECTED LIGHTNING NO x SOURCE [ppbv]

Lightning parameterization in model (flashes/km 2 /s): Land: ~CTH 4.9, Ocean: ~CTH 1.73 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/km 2 /s)

OZONE COMPARISON INTEX-NA SOUTHEAST U.S. Increasing lightning yield X4 to 500 mol/flash has ~10 ppbv effect on ozone NO 2 O3O3 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 NO x Emission (Tg N) Hemispheric ozone enhancement (Tg, %) Lightning (5.1%) Biomass burning (1.1%) Fossil fuel (6.2 %) All (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 PAN  NO x  HNO 3 strong  O 3 X10 Dilution Asian Plume  Asia  Europe INFLOW KEY RESULTS NO x stationary sources 22% Anthropogenic CO 60% Alt (km) 10 O 3 (ppbv) SOURCES AND EXPORT BB NA FF Lightning NO x /flash 4X larger than previously thought! Export well constrained  effects on O 3 & OPE SUMMERSPRING

3. SPACE BASED CONSTRAINTS ON SOIL NO x Most of what we know about processes responsible for soil NO x emissions is based on point measurements.

ATMOSPHERE BIOSPHERE NO is a low-yield product of nitrifying bacteria N 2 O(g), N 2 (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 NO x SOURCE INFERRED FROM SATELLITES Regional Distribution of soil NOx [Jaeglé et al., PNAS, 2005] GLOBAL: 8.9 Tg N/yr MIDLATITUDES: 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 NO 2 Column Aug 4, 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 Landtype Fertilizer emissions [Ramankutty] ENO x Hudman et al. [2010] CAN SOIL NO x EMISSIONS BE ROUTINELY VIEWED FROM SPACE?

MODELED SOIL NO x EMISSIONS Dry, warm conditions  anomalously high modeled June 2006 soil emissions Hudman et al. [2010]

SOIL EMISSION CONTRIBUTION TO NO 2 COLUMN June 2006 SOIL COLUMN / TOTAL COLUMNSOIL 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 NO x and day-to-day variability over Great Plains

OMI NO 2 JUNE INTERANNUAL VARIABILITY FOLLOWS PREDICTED SOIL NO x 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 NO 2 JUNE INTERANNUAL VARIABILITY FOLLOWS SOIL NO x Hudman et al. [2010] Suggests fertilizer induced emissions of soil NOx governs monthly variability in NO 2 column over Great Plains… what about pulsing?

PULSING OVER EASTERN SOUTH DAKOTA Pulsing event reaches 4x10 15 molec cm 2, ~ 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 NO x emissions remains a challenge. Because large scale features are well represented  ozone air quality

MEAN MAXIMUM 8-HR OZONE ENHANCEMENT DUE TO SOIL NO x Ozone enhancement due to soil NO x 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 NO x emissions from fires…here we want to look at processes….

CANADIAN FIRE WEATHER INDEX MODEL 2/3 day 15 day52 day Drying time Severity Rating WEATHER MOISTURE FIRE DANGER

Jul 1 – Aug Anomaly Strong Alaskan Ridge  record fires hPa 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 change in area burned RAIN VS. STAGNATION  UNCERTAINTY IN RESPONSE ++ Rain 500 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 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: NO x 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 CO 2 4.LIGHTNING: Lightning at midlatitudes produces X4 more NOx/flash than midlatitude/subtropical storms  ppbv ozone, comparable to anthropogenic emissions 5.SOIL: Soil NO x 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 Teams AURA Science Team