Mark Parrington School of GeoSciences, The University of Edinburgh

1. In situ observations of ozone photochemistry in boreal biomass burning plumes during the BORTAS campaign • Mark Parrington • School of GeoSciences, The University of Edinburgh

2. Outline • Motivation and overview of the BORTAS project • Boreal biomass burning activity in summer 2011 • Analysis of BORTAS aircraft measurements • Hydrocarbon ratios and photochemical ageing of observed biomass burning plumes • Evidence of ozone production in biomass burning plumes • Photostationary state chemistry calculations and instantaneous ozone production and loss • Summary and further work

3. Motivation • What is the influence of boreal biomass burning on the summertime tropospheric ozone distribution over the North Atlantic? • Is it possible to distinguish this influence in the context of other local sources of ozone precursors (e.g. anthropogenic emissions, lightning NOx)? • Many previous measurement campaigns (e.g. NARE, ICARTT, INTEX-B) have focussed on the influence of anthropogenic North American pollution and its transport across the North Atlantic. • During ITOP, in summer 2004, Canadian biomass burning plumes were intercepted in mid-Atlantic and Europe. • Biomass burning airmasses showed an unusual mixture of organic compounds within NOy (NO+NO2+PANs+HNO3+NO3+2N2O5+organic nitrates). • Much NOy was held as PAN but its abundance was much higher than predicted by theory and very sensitive to temperature and altitude. • It appears that NOy speciation holds the key to understanding O3 tendency (net P or L?) in biomass burning plumes. • No canonical O3:CO relationship. • The BORTAS project brings together measurements of the key species related to biomass burning outflow and quantify their relative impact on tropospheric ozone chemistry.

4. Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS) O3 production and loss within the outflow Composition and distribution of biomass burning outflow Resulting perturbation to atmospheric chemistry in the troposphere. International partners: NASA, CNRS, Environment Canada, Free University of Amsterdam, Dalhousie, Washington State

5. BORTAS measurement campaign • Aerosol numbers distributions, composition (AMS, SP2) • VOCs, alcohols, ketones, aldehydes, ethers (WAS) • NOy speciation (LIF) • HCN, HNO3, formic acid (CIMS) • O3 (UV-abs) • CH3CN/oxygenates (PTR-MS) • CO2, CH4, CO • j(NO2), j(O1D) • Semi-volatile VOCs • Based out of Halifax NS, Canada from 12 July to 3 August 2011. • FAAM BAe146 aircraft • 500 nautical mile range, approx. ceiling at 30000 ft • 15 flights (including science transit flights between UK and Canada via Azores, ~20 hours) • Support from ground-based, in situ, and satellite observations.

6. Support measurements for BORTAS Intensive sounding network:Links to Env. Canada, AEROCAN/AERONET (Sun photometer), CORALNet (Lidar) and Toronto Atmospheric Observatory (FTIR) Dalhousie Ground Station: Raman Lidar Sun photometerPARIS-IR FTIRPM2.5 NephelometerAMSWind profiler DA8 FTIR Ozone profiling Lidar • Daily ozonesonde launches: • Bratt’s Lake SKChurchill MBEgbert ONGoose Bay NLSable Island NSStony Plain ABYarmouth NS • Mt. Pico observatory, Azores:Ground-based measurement site in central Atlantic at 2200 m elevation.NRT measurements of ozone, CO, NOx, NOy, NMHCs, BC. • Satellite observations:IASI – NRT CO columns and profilesACE-FTS • TES special observations for North America/North Atlantic.

7. Overview of summer 2011 boreal fire activity • Observed fire hotspots for season up to 14 September show large concentration in north western ON. • Fires also concentrated in QC (earlier in fire season) and BC. • Aggregated MODIS fire counts for boreal North America (top) and Eurasia (bottom), for 1 May to 14 September. • Fire counts do not exceed 10,000 but generally greater than 100 in northern SK, BC, and eastern Siberia. http://cwfis.cfs.nrcan.gc.ca/en_CA/fm3maps/fwih http://firefly.geog.umd.edu/firemap/

8. Canadian fire activity: summer 2011 vs. 10 year average http://www.ciffc.ca/ • Number of fires through BORTAS-B considerably lower than 10 year average. • Burnt area lower than 10 year average through most of summer apart from week 17-23 July. • Slightly higher number of fires in AB and ON but significantly higher burnt area in AB, NT and ON. http://fire.cfs.nrcan.gc.ca/firereport/report-rapport-eng.php

9. Analysis of BORTAS aircraft measurements

10. Observed ozone distribution shows peak concentrations at 25 ppbv (measurements below 3 km) and 50 ppbv (background in free troposophere). Ozone mixing ratios have range of approx. 20 ppbv at highest CO values. Higher ozone values at lower CO values indicate mixing of other sources? Stratospheric influence? No discernible difference between ozone in background and plume air masses. Ozone distribution observed during BORTAS Frequency O3 / ppbv O3 / ppbv CO / ppbv

11. Evidence for ozone production in boreal biomass burning plumes reported from numerous measurement campaigns. Increase in ΔO3/ΔCO ratio with age of plume. No consensus about ozone tendency. Ozone production in biomass burning plumes Jaffe and Wigder (2012)

12. Organic compounds have a range of atmospheric lifetimes influenced by oxidation with OH. Evaluating combinations of organic species measured in biomass burning outflow tells us something about its chemical ageing. Chemical ageing of biomass burning plumes Parrish et al. (2007) • For a hydrocarbon, A, simple kinetic theory gives its concentration at time tM as: • Simultaneously evaluating another hydrocarbon, B, reduces need to know initial concentrations: • Which can be rearranged to give: • Comparing ratios of two different hydrocarbon ratios yields a linear relationship with the slope determined by the kinetic reaction rates:

13. Nonmethane hydrocarbon ratios tell us something about tropospheric oxidation and transport processes. Widely reported in the literature from aircraft and surface measurements [e.g. Parrish et al. (1992, 2007), Honrath et al. (2008), Jobson et al. (1994)]. NMHC ratios (n-butane/ethane vs. propane/ethane) measured during BORTAS are consistent with reported values from previous campaigns. Slope of linear fit to all BORTAS data = 1.50 in the range 1.20 - 2.26 for individual research flights. Hydrocarbon ratios Parrish et al. (1992) ln(n-butane/ethane) ICARTT ln(propane/ethane) ITCT 2K2 Parrish et al. (2007)

14. M = (kA − kC)/(kB − kC) describes the ageing of an airmass from a single source with no mixing. Initial mixing ratios (■) for boreal biomass burning emissions from flight b626 over fire source region in NW Ontario. Hydrocarbon ratios and photochemical age Mixing of fresh emissions into air masses with aged emissions ln(n-butane/ethane) Ageing due to oxidation by OH ln(propane/ethane)

15. Photochemical ages calculated from ln(propane):ln(ethane) ratio and assuming mean OH mixing ratio of 2×106 molecules/cm3. CO (VOC and LIF) measurements show similar ‘age spectra’ with largest peak at 2-3 days and secondary peak at 6-7 days. Ozone measurements show no obvious relationship with photochemical age. Estimate ozone production (or loss) from ratio of ozone enhancement over background, ΔO3, to ΔCO and ΔNOy. Photochemical age of plume measurements In plume Out of plume

16. Background concentrations of O3 (25 ppbv), CO (66 ppbv) and NOy (174 pptv) determined from 10th percentile of research flight data. Strongest correlation between ΔO3/ΔCO and photochemical age between 2-4 km (r = 0.67) and 4-6 km (r = 0.80). For all data, r = 0.57. Stronger correlations between ΔO3/ΔNOy and photochemical age with r = 0.81, 0.69, 0.94, and 0.77 for all, 2-4 km, 4-6 km, and 6-8 km data respectively. Evidence of ozone production in biomass burning outflow BORTAS plume measurements of ΔO3/ΔCO ΔO3/ΔCO / ppbv/ppbv BORTAS plume measurements of ΔO3/ΔNOy ΔO3/ΔNOy / ppbv/pptv Photochemical age / days

17. ΔO3/ΔCO measured during BORTAS aircraft campaign are consistent with observed ratios from previous measurement campaigns. Mean BORTAS values at higher end of reported means but median values in much better agreement possibly reflects large variability when considering all BORTAS research flights. At ages ≥5 days, mean and median BORTAS ratio more comparable to reported values for Siberian - indicates different emission source? NWT vs. NW Ontario? Need to verify source/age with back trajectories. This does not tell us anything about plume ozone chemistry. Evidence of ozone production in biomass burning outflow BORTAS Jaffe and Wigden (2012)

18. Photostationary state calculations • Ozone production from cycling of NOx, assuming steady state. • Peroxy radicals also interact with the NOx cycle to produce ozone: • Photostationary ratio will have a value of 1 if ozone only produced from NOx chemistry.

19. Photostationary ratio calculated from aircraft measurements indicate peroxy radicals influence ozone chemistry considerably. NOx conversion to NOy? Photostationary ratio of BORTAS plume measurements j2[NO2] / k1[NO][O3] CH3CN / ppbv

20. Plots show net instantaneous production and loss of ozone from NOx only reactions. Net loss generally at night (orange points) but also in day time on some flights (plume optical thickness?). Other chemical terms not included but required for calculating ozone production and loss terms (model simulations needed to do this): Net instantaneous ozone production Net P(O3) / 107 molec/cm3/s Net P(O3) / 107 molec/cm3/s Photochemical age / days Ozone / ppbv

21. ∑PNs CETEMPS Department of Physics University of L’Aquila, Italy , Italy ∑ANs Source and sink of O3 (slide from Piero Di Carlo) RO2 + NO → RO + NO2 RO’ + O2 → R’O + HO2 HO2 + NO → OH + NO2 2NO2+ hν + O2 → 2 O3 RO2 + NO → RONO2 ∑ANs is a good indicator of the photochemistry because O3 and ∑ANs have the same source ∑ANs

22. High values of ∑ANs and low values of ozone indicate suppressed ozone production (~6 molecules of ozone per molecule of ∑AN). note that the highest measurements were made at high solar zenith angle (i.e. no photochemistry leading to ozone loss through reaction with NO). Low values of ∑ANs and high values of ozone indicate higher photochemical ozone production (>500 molecules of ozone per molecule of ∑AN). Plotting the ratio of O3:NOz gives an estimate of the ozone production efficiency (OPE i.e. the number of molecules of ozone formed per molecule of NOx that is oxidized). reduced amount of data due limited availability of measured NOy. higher OPE indicates aged air masses and lower OPE indicates fresh emissions of pollutants. Towards understanding plume ozone chemistry Ozone / ppbv O3/NOz RONO2 (∑ANs) / ppbv RONO2 (∑ANs) / ppbv

23. The relationship between O3:NOz and NOx tells us something about the chemical regime within the plume. At high NOx, the plumes are in a VOC-limited regime with low OPE (i.e. freshly emitted plumes?). At low NOx, the plumes are in a NOx-limited regime with higher OPE (i.e. aged plumes). Towards understanding plume ozone chemistry Daytime plume measurements All plume measurements NOx-limited VOC-limited O3/NOz O3/NOz NOx / ppbv NOx / ppbv

24. Plume enhancements show strong linear relationship of relative to CO. No clear relationship for ozone implies more detailed analysis required. Hydrocarbon ratios are consistent with values reported in literature for previous measurement campaigns. Photochemical ages of observed biomass burning plumes calculated from propane:ethane ratio range from 0 to 10 days with peak CO, VOC, and NOy measurements at 2-3 days of ageing. Consistency with photochemical ages calculated from ABLE-3B and ARCTAS data. Evidence of ozone production in biomass burning outflow: Ratios of ΔO3/ΔCO and ΔO3/ΔNOy in the plume measurements show strong correlation (r > 0.7) to photochemical age in the free troposphere (2-8 km). Median values of ΔO3/ΔCO are consistent with measured values from previous campaign measurements in the boreal regions. Partitioning of NOy holds key to understanding the plume chemistry. Box model simulations are required to fill in gaps in the aircraft measurements (e.g. HOx/ROx). BORTAS campaign summary

25. Further work • Model analysis of biomass burning plume chemistry and impact on tropospheric ozone distribution. • detailed photochemical box modelling with MCM/CRI (in collaboration with York/Leeds). • 3-D modelling of plume chemistry and transport. • Data assimilation.

26. Model analysis of BORTAS measurements • Model analysis to evaluate aircraft and satellite observations. • Nested grid. • Global modelling with more detailed chemical mechanism.

27. Summary • The BORTAS project will bring together detailed modelling of plume chemistry and transport with in situ and satellite observations • Analysis is ongoing but first results suggest some promise for understanding chemistry in boreal biomass burning plumes • Papers from BORTAS will appear in a special issue of Atmospheric Chemistry and Physics in the coming months • http://www.atmos-chem-phys.net/special_issue263.html

28. Acknowledgements: BORTAS contributors • University of Edinburgh • Paul Palmer • Mark Parrington • Stephan Matthiesen • Rob Trigwell • Eddy Barratt • University of York • Ally Lewis • James Lee • Andrew Rickard • Sarah Moller • Steve Andrews • Peter Bernath • Keith Tereszchuk • University of Leeds • Jenny Young L’aquila University University of Manchester University of East Anglia • University of Toronto • Kaley Walker • Kim Strong • Cyndi Whaley • Debora Griffin • Dalhousie University • Tom Duck • Jim Drummond • Jeff Pierce • Randall Martin • Mark Gibson • Matt Seaboyer • Jonathan Franklin • Jason Hopper • Kimiko Sakamoto • Kaja Rotermund • Loren Bailey • Environment Canada • Lisa Langley • David Tarasick • Jane Liu • Steve Beauchamp • Richard Leaitch • Chris Fogarty • David Waugh • Doug Steeves • Lucy Chisholm • Naval Research Laboratory • Mike Fromm • Edward Hyer • B.J. Stocks Wildfire Investigations Ltd. • Brian Stocks • NASA GMAO • Steven Pawson • University of Sherbrooke • Norm O’Neill