Gordon conference - Atmospheric Chemistry. Big Sky, Montana, September 4-9 2005.Pico Mountain in the Azores Islands provides an ideal location for studies of the central N. Atlantic lower free troposphere. The PICO-NARE station has operated there since summer 2001. Here, we present key findings from summertime measurements, during 2001-2004. Main Findings: Anthropogenic and boreal wildfire emissions dominate variations in CO and have major impacts on O3, nitrogen oxides, non-methane hydrocarbons (NMHCs) and black carbon

Fialho, Paulo

Helmig, Detlev

Honrath, Richard

Kleissl, J.

Lapina, K.

Owen, Robert

Tanner, D. M.

Val Martin, Maria

Repositório da Universidade dos Açores

“Large-scale Impacts of Anthropogenic and Boreal Fire EmissionsApparent in Multi-year Free Tropospheric Observations in the AzoresR. E. Honrath1, M. Val Martin1, J. Kleissl1, R. C. Owen1, K. Lapina1, P. Fialho2, D. Helmig3, and D. Tanner31Department of Civil and Environmental Engineering, Michigan Technological University, U.S.2Grupo de Qumica e Fisica da Atmosfera, Universidade dos Acores, Portugal3Institute of Arctic and Alpine Research, University of Colorado, U.S.2. STATION OVERVIEWThe PICO-NARE station is located at 2225 m asl in the Portu-guese Azores Islands. Fig. 1 shows the location and exampleflow pathways bringing clean marine air, N. American pollution,and subarctic air potentially containing boreal fire emissions.Measurements at the station include: CO (2001-present), O3(2001, 2003-present), NO, NO2, and NOy (2002-2005), blackcarbon (2001-present), and NMHCs (2004-present). The sta-tion was recently shut down for the first time, for the 2005-06winter season. Pending new funding, it will reopen in spring2006 with new measurements of aerosol size distribution, CCN,and CO2, and resumption of NOx and NOy measurements.Free Tropospheric Air SamplingThe station altitude is well into the FT in all seasons [Figs. 2-3].Marine boundary layer (MBL) air only occasionally reaches thestation, due to daytime buoyant uplift (sunny periods with weakwinds) and mechanically driven uplift [1] (periods of strongwinds) [Figs. 3-4]. -160-140-120-100-80 -60 -40-2002001020304050607080900 2 4 6 8 10 12500100015002000monthheight [m]4. SIGNIFICANT IMPACTS OF N. AMERICAN ANTHROPOGENIC EMISSIONSEnhancements of CO, O3, BC, NOx, NOy and NMHCs levels above background also occur during flow from the U.S. [Fig. 8]. Mostof these events travel in the lower FT in a route governed by the Azores-Bermuda High and transient northerly lows [11], and typi-cally have a photochemical age of 5-10 days as indicated by the “NMHC clock” [Fig. 9] and backward trajectories (not shown).Evidence of significant O3 production downwind of N. AmericaIn 2001, few fires occurred, and nearly all periods of elevated CO and O3 occurred during U.S. outflow.The d[O3]/d[CO] slopes during these periods were significantly higher than those reported previouslynear the N. American coast, even after accounting for CO loss in transit and for declining North Ameri-can CO emissions [Fig. 10] [12]. This suggests an addition of significant amount of O3 to air reachingPico in 2001, relative to air near North America in the early 1990s.3c. Impact on summer O3 backgroundTo distinguish fire impacts on O3from effects of interannual variationsin flow pathways, we compare O3observations in 2 data subsets eachyear: Measurements in air flowingfrom N of 50N but with low CO (lowfire emissions) and those in air fromN of 50N but with elevated CO (likelyfire emissions). The fire-impacteddata exhibit ~20 ppbv higher medianO3, implying significant O3 impactseven after 7-10+ days transport [10].3b. Interannual VariabilitySummertime CO, BC and O3 levelswere higher in 2002 than in 2001, andmuch higher in 2003-2004 [Fig. 6].The CO and BC increases are attrib-uted to enhanced fires in Quebec in2002, and much enhanced fires inSiberia in 2003 and in Alaska andwestern Canada in 2004 [9,12].5. CONCLUSIONS AND FINAL REMARKS• Large boreal wildfires in 2002-2004 strongly impactedatmospheric composition over the central North Atlanticlower FT, and dominated the interannual variability of CO, O3and aerosol BC over 2001-2004. The frequency distribution ofO3 shifted toward higher levels, suggesting significantimpacts on the summertime O3 background over the region.• Nitrogen oxides levels during fire-impacted periods werevery high for such a remote region, suggesting significant con-tinuing O3 production in these well-aged boreal fire plumes.* This deserves further study since little is known about theimpact of boreal wildfires on the O3 levels in the NorthernHemisphere. Boreal wildfire activity is expected to increasein the future due to an increase in temperatures resultingfrom global climate change [15].• O3 enhancements during U.S. outflow transported to thesite over 5-10 days were significantly higher than thosereported from previous observations near North America.*Further work is needed to determine whether this indicateslarger O3 impacts from U.S. emissions than currently esti-mated.•The PICO-NARE station has been proved to be a valuableplatform for observations of the regional background and ofU.S. and boreal fire impacts. It is also impacted by Europeanand African emissions, although less frequently.*Additional climate-relevant measurements (CO2, aerosols,and CCN) are planned beginning in 2006 (pending new sup-port). Future PICO-NARE CO2 and O3 observations will beincorporated into the NOAA-CMDL record.*The Portuguese Met. Inst. and the Regional Government ofthe Azores are making significant progress toward convert-ing the station into a permanent GAW observatory in ~2008.1. INTRODUCTIONPico mountain in the Azores Islands provides an ideal locationfor studies of the central N. Atlantic lower free troposphere. ThePICO-NARE station has operated there since summer 2001.Here, we present key findings from summertime measurements,during 2001-2004.Main Findings: Anthropogenic and boreal wildfire emis-sions dominate variations in CO and have major impacts onO3, nitrogen oxides, non-methane hydrocarbons (NMHCs)and black carbon.FIGURE 1. Location of the PICO-NARE station in the Azores Islands. Top right: TheAzores Islands central group. Bottom right: a simulated view of the northwest side ofPico Island from an altitude of 6 km (NASA Worldwind).FIGURE 2. View of Pico mountain and of thestation near the cliff at the summit.FIGURE 3. Annual cycle of MBL height(dashed) based on FNL data. Alsoshown is the dividing streamlineheight (solid), which is the minimumheight of air transported to the summitby mechanical orographic uplifting.Lines connect medians, and error barsspan from 1st to 3rd quartiles.Ozone Distributions in NNA Flow: Low-CO and High-CO Subsets0 20 40 60 80 100Ozone (ppbv)0.00.10.20.30.4Fraction of Observations Ozone distribution, low-CO200120032004 Ozone distribution, high-CO200120032004Mon Apr 25 04:45:31 2005FIGURE 9. Apparent photochemical age determined from HC/HCratios. Blue symbols show all winter 2004--spring 2005 HC observa-tions; the red circles show data during the period of maximum mix-ing ratios around 4/18 and the green circles show data during theperiod of minimum mixing ratios around 4/20 [Fig. 8]. The lower andupper lines show the expected trend on this plot resulting from purephotochemical aging (reaction with OH) or mixing with backgroundair. Approximate ages since emission are written along the centerline, which reflects a combination of mixing and photochemicalaging.FIGURE 8. Observations during a spring 2005 apparent U.S.export event.  Arrows identify periods plotted in Fig. 9.FIGURE 10. Comparison of the 2001 Picod[O3]/d[CO] to slopes near North America inthe 1990s [12-14].REFERENCES[1] Kleissl J. et al.,Analysis and application of Sheppard’s airflow model to predict mechanical orographic lifting, JAM, in prepara-tion.[2] Andreae, M. O. et al., Emission of trace gases and aerosols from biomass burning, GBC, 15, 2001.[3] Val Martin, M. et al. Observations of enhanced nitrogen oxides levels from boreal wildfires in the North Atlantic lower free tro-posphere. GRL, in preparation.[4] Bertschi I.T and Jaffe D.A. Long-range transport of O3, CO, aerosol to the NE Pacific troposphere. during the summer of2003: Observations of smoke plumes from Asian boreal fires. JGR, 110, 2005.[5] Mauzerall, D. L. et al., Origin of tropospheric ozone at remote high northern latitudes in summer. JGR, 101,1996.[6] McKeen, S.A. et al., Ozone production from Canadian wildfires during June and July of 1995. JGR, 10.1029/2001JD000697,2002.[7] Wofsi S. C., et al., Atmospheric chemistry in the Arctic and subarctic: Influence of natural fires, industrial emissions, andstratospheric inputs. JGR, 97, 1992.[8] DeBell, L. J., et al. A major regional air pollution event in the northeastern United States caused by extensive forest fires inQuebec, Canada. JGR, 109, 2004.[9] Kasischke, E. S. et al., Influences of boreal fire emissions on Northern Hemisphere atmospheric carbon and carbon monox-ide. GBC, 19, 2005.[10] Lapina, K. et al., Impact of large-scale boreal fires on levels of tropospheric ozone in the Northern Hemisphere. GRL, inpreparation.[11] Owen, R.C. et al., Mechanism of North American export and transport to the central North Atlantic lower FT during July2003. JGR, in preparation.[12] Honrath, R.E et al., Regional and hemispheric impacts of anthropogenic and biomass burning emissions on summertimeCO and O3 in the North Atlantic lower FT. JGR, 119, 10.1029/2004JD005147, 2004.[13] Parrish, D.D. et al., Relationship between O3 and CO at surface sites in the North Atlantic region. JGR, 103, 1998.[14] Parrish, D.D. et al., Decadal change in carbon monoxide to nitrogen oxide ratio in U.S. vehicular emissions. JGR, 2002.[15] Stocks, B.J., et al., Large forest fires in Canada, 1959-1997. JGR, 108, 2003.PICO-NARE Site2225 ma) b)3. IMPACTS OF DISTANT BOREAL FIRES ARE LARGE3a. Fire-plume enhancements in CO, O3, NOx, NOy and black carbonMajor fires in Alaska and western Canada repeatedly impacted our station during summer 2004. Extreme enhancements of CO, O3, NOx, NOy,BC, and NMHCs (not shown) occurred during these periods [Fig. 4].• d[O3]/d[CO] was similar to some previous reports for well-aged forest fire plumes, although in some cases O3 production was sup-pressed, especially in the most concentrated part of the plume [Fig. 5a].• d[NOy]/d[CO] was a significant fraction of the estimated NOx/CO emission ratio [2] and only moderately smaller than previous measure-ments much closer to fires [Fig.5b], indicating limited NOy removal during transport to the site and likely O3 formation downwind [3].ACKNOWLEDGEMENTSWe thank Dr. Andreas Stohl for sharing simulations of the FLEXPART model. Technical andlogistical support was provided by Mike Dziobak (MTU). Additional field assistance was providedby Forca Aerea Portuguesa, and Bombeiros Voluntarios do Madalena do Pico. Jessica Strane(MTU) assisted with the analysis of the airflow events. This work was supported by NOAA/OGPgrant NA030AR4510002 and NA16GP1658, and NSF grant ATM-0215843.FIGURE 7. Frequency distributions of O3observations in northern North America flowonly, divided into high-CO and low-CO sub-sets.Richard Honrath: reh@mtu.eduJul 2212:00Jul 2218:00Jul 2300:00Jul 2306:00Jul 2312:0050150250CO (ppbv)205080Ozone (ppbv)06501300NOy (pptv)0350700Black Carbon (ng m-3)Aug 3100:00Sep 0100:00Sep 0200:00Sep 0300:0050150250CO (ppbv)205080Ozone (ppbv)06501300NOy, NOx (pptv)0350700Black Carbon (ng m-3)Jul 0100:00Jul 0600:00Jul 1200:00Jul 1700:00Jul 2300:00Aug 0100:00020040060080010001200NOy, NOx (pptv)-50050100150200250CO, O3 (ppbv); BC/4 (ng/m3)NOyNOxCOO3BCFLX-BBAug 0100:00Aug 0700:00Aug 1300:00Aug 2000:00Aug 2600:00Sep 0400:00020040060080010001200NOy, NOx (pptv)-50050100150200250CO, O3 (ppbv); BC/4 (ng/m3)NOyNOxCOO3BCFLX-BBFIGURE 4. CO, O3, NOx, NOy, BC, and FLEXPART boreal fire CO tracer during summer 2004. Periodsmarked by bars along the top of the plot are events attributed to boreal fire emissions (based onanalyses of back trajectories, MODIS images, correlations among the species, and FLEXPART simu-lations [A. Stohl, see Acknowledgements]). Data during these periods are plotted in Fig. 5. Hatchedareas show periods when buoyant and mechanically driven upslope flow may have impacted thesite; these periods are not considered in the analyses. Also shown are two events in more detail.Ozone vs CO50 100 150 200 250CO (ppbv)20304050607080O3 (ppbv)ABLE-3A/BMcKeen02ABLE-3B(max)Bertschi05maxNOy vs CO50 100 150 200 250CO (ppbv)020040060080010001200NOy (pptv)Andreae01DeBell04ABLE-3A(avg)ABLE-3B(avg)FIGURE 5. Scatter plots of O3 and NOy against CO during thesummer 2004 boreal fire events. Colors highlight periods with dif-fering O3 enhancements. Also shown are O3-CO and NOy-COenhancement ratios from selected previous studies [2,4-8].FIGURE 6. Cumulative distributions of allhourly average observations of BC, CO and O3during the summers of 2001-2004.Absorption expressed as Black Carbon0 100 200 3000.00.20.40.60.81.0Black Carbon (ng m-3)2001200220032004CO0 50 100 150 2000.00.20.40.60.81.0CO (ppbv)2001200220032004Ozone0 20 40 60 800.00.20.40.60.81.0O3 (ppbv)2001200220032004Thu Jun 23 19:24:46 2005NOTE: O3 data unavailableduring summer 2002a) b)Generator Hikers’ carsPICO-NARE stationMBL heightAltitude reaching summitStation altitude: 2225 mSpring 2005 event: CO, O3, NOy, and alkanes04/15/0500:0004/18/0500:0004/21/0500:0004/24/0500:0004/27/0500:0004/30/0500:00-50050100150CO, O3 (ppbv)020040060080010001200ethane/5, n-butane, propane, NOy (pptv)COO3NOyethane/5propanen-butaneWed Aug 31 08:42:25 2005

Large-scale impacts of anthropogenic and boreal fire emissions apparent in multi-year free tropospheric observations in the Azores.

Large-scale impacts of anthropogenic and boreal fire emissions apparent in multi-year free tropospheric observations in the Azores.

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