In situ observations of ozone photochemistry in boreal biomass burning plumes during the

BORTAS campaign

Mark ParringtonSchool of GeoSciences, The University of Edinburgh

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

• 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.

Motivation

Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS)

Resulting perturbation to atmospheric chemistry in the troposphere.

Composition and distribution of biomass burning outflow

O3 production and loss within the outflow

International partners: NASA, CNRS, Environment Canada, Free University of Amsterdam, Dalhousie, Washington State

BORTAS measurement campaign

• 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.

• 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

Support measurements for BORTAS

Raman LidarSun photometerPARIS-IR FTIRPM2.5 NephelometerAMSWind profilerDA8 FTIR Ozone profiling Lidar

Intensive sounding network:Links to Env. Canada, AEROCAN/AERONET (Sun photometer), CORALNet (Lidar) and Toronto Atmospheric Observatory (FTIR)

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.

Dalhousie Ground Station:

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/

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

Analysis of BORTAS aircraft measurements

Ozone distribution observed during BORTASO

3 /

ppbv

CO / ppbv

O3 / ppbv

Frequency

• 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 production in biomass burning plumes

Jaffe and Wigder (2012)

• 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.

Chemical ageing of biomass burning plumes

• 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.

• For a hydrocarbon, A, simple kinetic theory gives its concentration at time tM as:

• Which can be rearranged to give:

• Simultaneously evaluating another hydrocarbon, B, reduces need to know initial concentrations:

• Comparing ratios of two different hydrocarbon ratios yields a linear relationship with the slope determined by the kinetic reaction rates:

Parrish et al. (2007)

Hydrocarbon ratios

Parrish et al. (2007)

ln(propane/ethane)ln

(n-b

uta

ne/e

thane)

ICARTT

ITCT 2K2

Parrish et al. (1992)

• 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.

• 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

ln(propane/ethane)

ln(n

-buta

ne/e

thane)

Ageing due to oxidation by OH

Mixing of fresh emissions into air masses with aged emissions

Photochemical age of plume measurements

• 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.

In plume

Out of plume

Evidence of ozone production in biomass burning outflow

• 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.

Photochemical age / days

ΔO

3/Δ

NO

y /

ppbv/p

ptv

ΔO

3/Δ

CO

/ p

pbv/p

pbv

BORTAS plume measurements of ΔO3/ΔNOy

BORTAS plume measurements of ΔO3/ΔCO

Evidence of ozone production in biomass burning outflow

0.005-0.731 (n = 21)

0.15 (0.07) ± 0.19

0.02-1.30 (n = 133)

0.21 (0.13) ± 0.22

0.004-1.437 (n = 53)

0.52 (0.44) ± 0.30

Range of ΔO3/ΔCO(# plume

measurements)

Mean (median)ΔO3/ΔCO

BORTAS

Jaffe and Wigden (2012)

• 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.

Photostationary state calculations

• 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.

• Ozone production from cycling of NOx, assuming steady state.

Photostationary ratio of BORTAS plume measurements

CH3CN / ppbv

j 2[N

O2]

/ k 1

[NO

][O

3]

• Photostationary ratio calculated from aircraft measurements indicate peroxy radicals influence ozone chemistry considerably.

• NOx conversion to NOy?

• 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 productionN

et

P(O

3)

/ 1

07 m

ole

c/cm

3/s

Net

P(O

3)

/ 1

07 m

ole

c/cm

3/s

Photochemical age / days Ozone / ppbv

Source and sink of O3 (slide from Piero Di Carlo)

, Italy

CETEMPSDepartment of PhysicsUniversity of L’Aquila, Italy

∑PNs

∑ANsRO2 + 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

• 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 chemistryO

zone /

ppbv

RONO2 (∑ANs) / ppbv

O3/N

Oz

RONO2 (∑ANs) / ppbv

• 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

NOx / ppbv

O3/N

Oz

NOx / ppbv

O3/N

Oz

VOC-limitedNOx-limited

All plume measurements Daytime plume measurements

BORTAS campaign summary

• 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).

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.

Model analysis of BORTAS measurements

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

• Model analysis to evaluate aircraft and satellite observations.

• Nested grid.

• Global modelling with more detailed chemical mechanism.

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

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

University of Toronto•Kaley Walker•Kim Strong•Cyndi Whaley•Debora Griffin

Naval Research Laboratory•Mike Fromm•Edward Hyer

University of Sherbrooke•Norm O’Neill

B.J. Stocks Wildfire Investigations Ltd.•Brian Stocks

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

Acknowledgements: BORTAS contributors

NASA GMAO•Steven Pawson

University of ManchesterUniversity of East Anglia

L’aquila University