References

ACP

Atmospheric Chemistry and Physics

ACP

1680-7324

Copernicus GmbH

Göttingen, Germany

10.5194/acp-11-11431-2011

Interannual variability of ozone and carbon monoxide at the Whistler high elevation site: 2002–2006

Macdonald

A. M.

¹ Anlauf

K. G.

¹ Leaitch

W. R.

¹ Chan

¹ Tarasick

D. W.

Science and Technology Branch, Environment Canada, 4905 Dufferin Street, Toronto, Ontario, Canada

17 11 2011

11 22 11431 11446

This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

This article is available from http://www.atmos-chem-phys.net/11/11431/2011/acp-11-11431-2011.html

The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/11431/2011/acp-11-11431-2011.pdf

In spring 2002, an atmospheric measurement site was established at the peak of Whistler Mountain in British Columbia, Canada to measure trace gases, particle chemistry and physics, and meteorology. This paper uses continuous measurements from March 2002 to December 2006 to investigate the influence of trans-Pacific transport and North American forest fires on both O3 and CO at Whistler. Annual mean mixing ratios of O3 and CO were 41 ppbv (monthly means of 35–48 ppbv) and 145 ppbv (monthly means of 113–177 ppbv) respectively with both species exhibiting an annual cycle of late-winter to early-spring maxima and summer minima. The absence of a broad summer O3 peak differs from previously-reported high altitude sites in the western US. The highest monthly-averaged O3 and CO mixing ratios relative to the 5-yr monthly means were seen in fall 2002 and spring 2003 with increased O3 and CO of 10 % and 25 % respectively. These increases correspond to anomalously-high values reported at other Northern Hemisphere sites and are attributed to fires in the Russian Federation. Air mass back trajectory analysis is used to associate the mean enhancements of O3 and CO with trans-Pacific transported or North American air masses relative to the Pacific background. Mean values of the enhancements for March to June in trans-Pacific air masses were 6 ppbv and 16 ppbv for O3 and CO respectively. In summers 2002–2006, higher CO and O3 mixing ratios were almost always observed in North American air masses and this relative enhancement co-varied for each year with the western US and Canada total wildfire area. The greatest enhancements in O3 and CO were seen in 2004, a record year for forest fires in Alaska and the Yukon Territory with average O3 and CO mixing ratios 13 and 43 ppbv above background values.

References 1

Ambrose, J. L., Reidmiller, D. R., and Jaffe, D. A.: Causes of high O3 in the lower free troposphere over the Pacific Northwest as observed at the Mt. Bachelor Observatory, Atmos. Environ., 45, 5302–5315, 2011.

Andreae M. O., Berresheim, H., Andreae, T. W., Kritz, M. A., Bates, T. S., Merrill J. T.: Vertical distribution of dimethylsulfide, sulfur dioxide, aerosol ions, and radon over the northeast Pacific Ocean, J. Atmos. Chem., 6, 149–173, 1988.

Andrews, E.,Ogren, J. A., Bonasoni, P., Marinoni, A., Cuevas, E., Rodriguez, S., Sun, J. Y., Jaffe, D. A., Fischer, E. V., Baltensperger, U., Weingartner, E., Collaud Cohen, M., Sharma, S., Macdonald, A. M., Leaitch, W. R., Lin, N.-H., Laj, P., Arsov, T., Kalapov, I., Jefferson, A., and Sheridan, P: Climatology of aerosol radiative properties in the free troposphere, Atmos. Res., 102, 365–393, http://dx.doi.org/10.1016/jatmosres.2011.08.017doi:10.1016/jatmosres.2011.08.017, 2011.

Bailey, R., Barrie, L. A., Halsall, C. J., Fellin, P., Muir, D. C. G.: Atmospheric organochlorine pesticides in the western Canadian Arctic: Evidence of transpacific transport, J. Geophys. Res., 105, 11805–11811, 2000.

Bertschi I. T. and Jaffe, D. A.: Long-range transport of ozone, carbon monoxide, and aerosols to the NE Pacific troposphere during the summer of 2003: observations of smoke plumes from Asian boreal fires, J. Geophys. Res., 110, D05303, http://dx.doi.org/10.1029/2004JD005135doi:10.1029/2004JD005135, 2005.

Chan, E. and Vet, R. J.: Baseline levels and trends of ground level ozone in Canada and the United States, Atmos. Chem. Phys., 10, 8629–8647, http://dx.doi.org/10.5194/acp-10-8629-2010doi:10.5194/acp-10-8629-2010, 2010.

Cooper, O. R., Parrish, D. D., stohl, A., Trainer, M., Nedelec, P., Thouret, V., Cammas, J. P., Oltmans, S. J., Johnson, B. J., Tarasick, D., Leblanc, T., McDermid, I. S., Jaffe, D., Gao, R., Stith, S., Ryerson, T., Aikin, K., Campos, T., Weinheimer, A., and Avery, M. A.: Increasing springtime ozone mixing ratios in the free troposphere over western North America, Nature, 463, 344–348, 2010.

Crutzen, P. and Andreae, M O.: Biomass burning in the tropics: Impact on atmospheric chemistry and biogeochemical cycles, Science, 250, 1669–1678, 1990.

Dalsoren, S. B., Eide, M. S., Myhre, G., Endressen, O., Isaksen, I. S. A., and Fuglestvedt, J. S.: Impacts of the Large Increase in International Ship Traffic 2000–2007 on Tropospheric Ozone and Methane, Environ. Sci. Technol., 44, 2482–2489, 2010.

D'Amours, R. and Page, P.: Atmospheric transport models for environmental emergencies. http://collaboration.cmc.ec.gc.ca/cmc/cmoi/product_guide/docs/lib/model-eco_urgences_e.pdf, Canadian Meteorological Centre, Environment Canada, Montreal, Quebec, 7 pp., 2001.

DeBell L. J., Talbot, R. W., Dibb, J. E., Munger, J. W., Fischer, E. V., and Frolking, S. E.: A major regional air pollution event in the northeastern United States caused by extensive forest fires in Quebec, Canada, J. Geophys. Res., 109, D19305, http://dx.doi.org/10.1029/2004JD004840doi:10.1029/2004JD004840, 2004.

Fiore, A. M., Jacob, D. J., Bey, I., Yantosca, R. M., Field, B. D., Fusco, A. C., and Wilkinson, J. G.: Background ozone over the United States in summer: Origin, trend, contribution to pollution episodes, J. Geophys Res., 107, 4275, http://dx.doi.org/10.1029/2001JD000982doi:10.1029/2001JD000982, 2002.

Galanter, M., Levy, H.,~and Carmichael, G R.: Impacts of biomass burning on tropospheric CO, NOx, and O3. J. Geophys. Res., 105, 6633–6653, 2000.

Gallagher, J. P., McKendry, I. G., Macdonald, A. M., and Leaitch, W. R.: Seasonal and Diurnal Variations in Aerosol Concentration on Whistler Mountain: Boundary Layer Influence and Synoptic Scale Controls, J. Appl. Meteorol. Clim., 50, 2210–2222, http://dx.doi.org/10.1175/JAMC-D-11-028.1doi:10.1175/JAMC-D-11-028.1, 2011.

Goldammer, J. G., Sukhinin, A., and Davidenko, E. P.: International Forest Fire News (IFFN) No. 37 (June–December 2007, in prep.) Advance Publication of Wildland Fire Statistics for Russia 1992–2007, ISSN 1029-0864, 2007.

Harris, J. M., Oltmans, S. J., Dlugokencky, E. J., Novelli, P. C., Johnson, B. J., and Mefford, T.: An investigation into the source of the springtime tropospheric ozone maximum at Mauna Loa observatory, Geophys. Res. Lett., 25, 1895–1898, 1998.

Heald, C. L., Jacob, D. J., Fiore, A. M., Emmons, L. K., Gille, J. C., Deeter, M. N., Warner, J., Edwards, D. P., Crawford, J. H., Hamlin, A. J., Sachse, G. W., Browell, E. V., Avery, M. A., Vay, S. A., Westberg, D. J., Blake, D. R., Singh, H. B., Sandholm, S. T., Talbot, R. W., and Fuelberg, H. E.: Asian outflow and trans-Pacific transport of carbon monoxide and ozone pollution: An integrated satellite, aircraft, and model perspective, J. Geophys. Res., 108(D24), http://dx.doi.org/10.1029/2003JD003507doi:10.1029/2003JD003507, 2003.

Holloway, T., Levy, H., and Kasibhatla, P.: Global distribution of carbon monoxide, J. Geophys. Res., 105, 12123–12147, 2000.

Honrath, R. E., Owen, R. C., Val Martin, M., Reid, J. S., Lapina, K., Fialho, P., Dziobak, M. P., Kleissl, J., and Westphal, D. L.: Regional and hemispheric impacts of anthropogenic and biomass burning emissions on summertime CO and O3 in the North Atlantic lower free troposphere, J. Geophys. Res., 109, D24310, http://dx.doi.org/10.1029/2004JD005147doi:10.1029/2004JD005147, 2004.

Hudman, R. C., Murray, L. T., Jacob, D. J., Millet, D. B., Turquety, S., Wu, S., Blake, D. R., Goldstein, A. H., Holloway, J., and Sachse, G. W.: Biogenic versus anthropogenic sources of CO in the United States, Geophys. Res. Lett., 35, L04801, http://dx.doi.org/10.1029/2007GL032393doi:10.1029/2007GL032393, 2008.

Husar, R. B., Tratt, D. M., Schichtel, B. A., Falke, S. R., Li, F., Jaffe, D., Gasso, S., Gill, T., Laulainen, N. S., Lu, F., Reheis, M. C., Chun, Y., Westphal, D., Holben, B. N., Gueymard, C., McKendry, I., Kuring, N., Feldman, G. C., McClain, C., Frouin, R. J., Merrill, J., DuBlois, D., Vignola, F., Murayama, T., Nickovic, S., Wilson, W. E., Sassen, K., Sugimoto, N., and Malm, W. C.: Asian dust events of April 1998, J. Geophys. Res., 106, 18317–18330, 2001.

Jacob, D. J., Logan, J. A., and Murti, P. P.: Effect of rising Asian emissions on surface ozone in the United States, Geophys. Res. Lett., 26, 2175-2178, 1999.

Jaffe D., Anderson, T., Covert, D., Kothenruther, R., Trost, B. Danielson, J. Simpson, W. Berntsen, T., Karlsdottir, S., Blake, D., Harris, J., Carmichael, G., and Ino, I.: Transport of Asian pollution to North America, Geophys. Res. Lett., 26, 711–714, 1999.

Jaffe, D., McKendry, I., Anderson, T., and Price, H.: Six "new" episodes of trans-Pacific transport of air pollutants, Atmos. Environ., 37, 391–404, 2003.

Jaffe, D., Bertschi, I., Jaegle, L., Novelli, P., Reid, J.S., Tanimoto, H., Vingarzan, R., and Westphal, D.: Long-range transport of Siberian biomass burning emissions and impact on surface ozone in western North America, Geophys. Res. Lett., 31, L16106, http://dx.doi.org/10.1029/2004GL020093doi:10.1029/2004GL020093, 2004.

Jaffe, D. and Ray, J.: Increase in surface ozone at rural sites in the western US, Atmos. Environ., 41, 5452–5463, 2007.

Jaffe, D., Chand, D., Hafner, W., Westerling, A., and Spracklen, D.: Influence of Fires on O3 Concentrations in the Western U.S., Environ. Sci. Technol., 42, 5885–5891, http://dx.doi.org/10.1021/es800084kdoi:10.1021/es800084k, 2008.

Jaffe, D.: Relationship between Surface and Free Tropospheric Ozone in the Western U.S., Environ. Sci. Technol., 45, 432–438, 2011.

Kleissl, J., Honrath, R. E., and Henriques, d. V.: Analysis and application of Sheppard's airflow model to predict mechanical orographic lifting and the occurrence of mountain clouds, J. Appl. Meteorol. Clim., 45, 1376–1387, 2006.

Kleissl, J., Honrath, R. E., Dziobak, M. P., Tanner, D., ValMartin, M., Owen, R. C., and Helmig, D.: Occurrence of upslope flows at the Pico mountaintop observatory: A case study of orographic flows on a small volcanic island, J. Geophys. Res., 112, D10S35, http://dx.doi.org/10.1029/2006JD007565doi:10.1029/2006JD007565, 2007.

Klock, R. and Mullock, J.: The Weather of British Columbia – Graphic Area Forecast 31, Nav Canada, 221 pp., 2001.

Kritz, M. A., LeRoulley, J. C., and Danielson, E. F.: The China clipper-fast advective transport of radon-rich air from the Asian boundary layer to the upper troposphere near California, Tellus, 42B, 46–61, 1990.

Lapina, K., Honrath, R. E., Owen, R. C., Val Martin, M., and Pfister, G.: Evidence of significant large-scale impacts of boreal fires on ozone levels in the midlatitude Northern Hemosphere free troposphere, Geophys. Res., Lett., 33, L10815, http://dx.doi.org/10.1029/2006GL025878doi:10.1029/2006GL025878, 2006.

Leaitch, W.R., Macdonald, A. M., Anlauf, K G.,~ Liu, P S K.,~Toom-Sauntry, D.,~Li, S.-M.,~Liggio, J.,~Hayden, K., Wasey, M.A.,~Russell, L M.,~Takahama, S.,~Liu, S.,~van~Donkelaar, A., Duck, T.,~Martin, R V.,~Zhang, Q.,~Sun, Y.,~McKendry, I.,~Shantz, N C.,~and Cubison, M.: Evidence for Asian dust effects from aerosol plume measurements during INTEX-B 2006 near Whistler, BC, Atmos. Chem. Phys., 9, 3523–3546, http://dx.doi.org/10.5194/acp-9-3523-2009doi:10.5194/acp-9-3523-2009, 2009.

Liang, Q., Jaegle, L., Jaffe, D.A., Weiss-Penzias, P., Heckman, A., and Snow, J. A.: Long-range transport of Asian pollution to the northeast Pacific: Seasonal variations and transport pathways of carbon monoxide, J. Geopyhs. Res., 109, D23S07, http://dx.doi.org/10.1029/2003JD004402doi:10.1029/2003JD004402, 2004.

Liang, Q., Jaegle, L., Hudman, R. C., Turquety, S., Jacob, D. J., Avery, M. A., Browell, E. V., Sachse, G. W., Blake, D. R., Brune, W., Ren, X., Cohen, R. C., Dibb, J. E., Fried, A., Fuelberg, H., Porter, M., Heikes, B. G., Huey, G., Singh, H. B., and Wennberg, P. O.: Summertime influence of Asian pollution in the free troposphere over North America, J. Geophys., Res., 112, D12S11, http://dx.doi.org/10.1029/2006JD007919doi:10.1029/2006JD007919, 2007.

Mauzerall, D. L., Logan, J. A., Jacob, D. J., Anderson, B. E., Blake, D. R., Bradshaw, J. D., Heikes, B., Sachse, G. W., Singh, H., and Talbot, B.: Photochemistry in biomass burning plumes and implications for tropospheric ozone over the tropical South Atlantic, J. Geophys. Res., 103, 8401–8423, 1998.

McKeen, S. A., Wotawa, G. Parrish, D. D., Holloway, J. S., Buhr, M. P., Hubler, G., Fehsenfeld, F. C., and Meagher, J. F.: Ozone production from Canadian wildfires during June and July of 1995, J. Geophys. Res., 107, 4192, http://dx.doi.org/10.1029/2001JD000697doi:10.1029/2001JD000697, 2002.

McKendry, I. G., Hacker, J. P., Stull, R., Sakiyama, S., Mignacca, D., and Reid, K.: Long-range transport of Asian dust to the Lower Fraser Valley, British Columbia, Canada, J. Geophys. Res., 106, 18361–18370, 2001.

Novelli, P. C., Masarie, K. A., and Lang, P. M.: Distributions and recent changes of carbon monoxide in the lower troposphere, J. Geophys. Res., 103, 19015–19033, 1998.

Novelli, P. C., Masarie, K. A. Lang, P. M., Hall, B. D., Myers, R. C., and Elkins, J. W.: Reanalysis of tropospheric CO trends: effects of the 1997–1998 wildfires, J. Geophys Res., 108, 4464, http://dx.doi.org/10.1029/2002JD003031doi:10.1029/2002JD003031, 2003.

Oltmans, S. J., Lefohn, A. S., Harris, J. M., and Shadwick, D. S.: Background ozone levels of air entering the west coast of the US and assessment of longer-term changes, Atmos. Environ., 42, 6020–6038, 2008.

Oltmans, S. J., Hofmann, D. J., Lathrop, J. A., Harris, J. M., Komhyr, W. D., and Kuniyuki, D.: Tropospheric ozone during Mauna Loa Observatory Photochemistry Experiment 2 compared to long-term measurements from surface and ozonesonde observations, J. Geophys. Res., 101, 14569-14580, 1996.

Parrish, D. D., Holloway, J. S., Trainer, M., Murphy, P. C., Fehsenfeld, F. C., Forbes, G. L.: Export of north American Ozone Pollution to the North Atlantic Ocean, Science, 259, 1436–1439, 1993.

Parrish, D. D., Trainer, M., Holloway, J. S., Yee, J. E., Warshawsky, M. S., Fehsenfeld, F., Forbes, G. L., and Moody, J. L.: Relationships between ozone and carbon monoxide at surface sites in the North Atlantic region, J. Geophys. Res., 103, 13357–13376, 1998.

Parrish, D. D., Millet, D. B., and Goldstein, A. H.: Increasing ozone in marine boundary layer inflow at the west coasts of North America and Europe, Atmos. Chem. Phys., 9, 1303-1323, http://dx.doi.org/10.5194/acp-9-1303-2009doi:10.5194/acp-9-1303-2009, 2009.

Parrish, D. D., Aikin, K. C., Oltmans, S. J., Johnson, B. J., Ives, M., and Sweeny, C.: Impact of transported background ozone inflow on summertime air quality in a California ozone exceedance area, Atmos. Chem. Phys., 10, 10093–10109, http://dx.doi.org/10.5194/acp-10-10093-2010doi:10.5194/acp-10-10093-2010, 2010.

Pfister, G. G., Emmons, L. K., Hess, P. G., Honrath, R., Lamarque, J.-F., Val Martin, M., Owen, R. C., Avery, M. A., Browell, E. V., Holloway, J. S., Nedelec, P., Purvis, R., Ryerson, T.B., Sachse, G. W., and Schlager, H.: Ozone production from the 2004 North American boreal fires, J. Geophys. Res., 111, D24S07, http://dx.doi.org/10.1029/2006JD007695doi:10.1029/2006JD007695, 2006.

Pfister G.G., Wiedinmyer, C., and Emmons, L.K.: Impacts of the fall 2007 California wildfires on surface ozone: Integrating local observations with global model simulations, Geophys. Res. Lett., 35, L19814, http://dx.doi.org/10.1029/2008GL034747doi:10.1029/2008GL034747, 2008.

Reidmiller, D. R., Jaffe, D. A., Chand, D., Strode, S., Swartzendruber, P., Wolfe, G. M., and Thornton, J. A.: Interannual variability of long-range transport as seen at the Mt. Bachelor observatory, Atmos. Chem. Phys., 9, 557–572, http://dx.doi.org/10.5194/acp-9-557-2009doi:10.5194/acp-9-557-2009, 2009.

Simpson, I. J., Akagi, S. K., Barletta, B., Blake, N. J., Choi, Y., Diskin, G. S., Fried, A., Fuelberg, H. E., Meinardi, S., Rowland, F. S., Vay, S. A., Weinheimer, A. J., Wennberg, P. O., Wiebring, P., Wisthaler, A., Yang, M., Yokelson, R. J., and Blake, D. R.: Boreal forest fire emissions in fresh Canadian smoke plumes: C1-C10 volatile organic compounds (VOCs), CO2, CO, NO2, NO, HCN and CH3CN, Atmos. Chem. Phys., 11, 6445–6463, http://dx.doi.org/10.5194/acp-11-6445-2011doi:10.5194/acp-11-6445-2011, 2011.

Slowik, J. G., Stroud, C., Bottenheim, J. W., Brickell, P. C., Chang, R. Y.-W., Liggio, J., Makar, P. A., Martin, R. V., Moran, M. D., Shantz, N. C., Sjostedt, S. J., van Donkelaar, A., Vlasenko, A., Wiebe, H. A., Xia, A. G., Zhang, J., Leaitch, W. R., and Abbatt, J. P. D.: Characterization of a large biogenic secondary organic aerosol event from eastern Canadian forests, Atmos. Chem. Phys., 10, 2825–2845, http://dx.doi.org/10.5194/acp-10-2825-2010doi:10.5194/acp-10-2825-2010, 2010.

Singh, H. B., Brune, W. H., Crawford, J. H., Flocke, F., and Jacob, D. J.: Chemistry and transport of pollution over the Gulf of Mexico and the Pacific: spring 2006 INTEX-B campaign overview and first results, Atmos. Chem. Phys., 9, 2301–2318, http://dx.doi.org/10.5194/acp-9-2301-2009doi:10.5194/acp-9-2301-2009, 2009.

Stohl A., Eekhardt, S., Forster, C., James, P., and Spichtinger, N.: On the pathways and timescales of intercontinental air pollution transport, J. Geophys. Res, 107, 4684, http://dx.doi.org/10.1029/2001JD001396doi:10.1029/2001JD001396, 2002.

Talbot, R. W., Dibb, J. E., Lefer, B. L., Bradshaw, J. D., Sandholm, S. T., Blake, D. R., Blake, N. J., Sachse, G. W., Collins Jr., J. E., Heikes, B. G., Merrill, J. T., Gregory, G. L., Anderson, B. E., Singh, H. B., Thornton, D. C., Bandy, A. R., and Pueschel, R. F.: Chemical characteristics of continental outflow from Asia to the troposphere over the western Pacific Ocean during February-March 1994: Results from PEM-West B, J. Geophys. Res., 102, 28255–28274, 1997.

Tarasick, D. W. and Slater, R.: Ozone in the Troposphere: Measurements, Climatology, Budget, and Trends, Atmos.-Ocean, 46, 93–115, http://dx.doi.org/10.3137/ao.460105doi:10.3137/ao.460105, 2008.

Van der Werf, G. R., Randerson, J. T., Giglio, L., Collatz, G. J., Kasibhatla, P. S., and Arellano Jr., A. F.: Interannual variability in global biomass burning emissions from 1997 to 2004, Atmos. Chem. Phys., 6, 3423–3441, http://dx.doi.org/10.5194/acp-6-3423-2006doi:10.5194/acp-6-3423-2006, 2006.

Val Martin, M., Honrath, R. E., Owen, R. C., Pfister, G., Fialho, P., and Barata, F.: Significant enhancements of nitrogen oxides, black carbon, and ozone in the North Atlantic lower free troposphere resulting from North American boreal wildfires, J. Geophys. Res., 111, D23S60, http://dx.doi.org/10.1029/2006JD007530doi:10.1029/2006JD007530, 2006.

VanCuren, R. A. and Cahill, T. A.: Asian aerosols in North America: frequency and concentration of fine dust, J. Geophys. Res., 107, 4804, http://dx.doi.org/10.1029/2002JD002204doi:10.1029/2002JD002204, 2002.

van Donkelaar, A., Martin, R. V., Leaitch, W. R., Macdonald, A. M., Walker, T. W., Streets, D. G., Zhang, Q., Dunlea, E. J., Jimenez, J. L., Dibb, J. E., Huey, L. G., Weber, R., and Andreae, M. O.: Analysis of aircraft and satellite measurements from the Intercontinental Chemical Transport Experiment (INTEX-B) to quantify long-range transport of East Asian sulfur to Canada, Atmos. Chem. Phys., 8, 2999–3014, http://dx.doi.org/10.5194/acp-8-2999-2008doi:10.5194/acp-8-2999-2008, 2008.

Vingarzen, R.: A review of surface ozone background levels and trends, Atmos. Environ., 38, 3431–3442, 2004.

Walker, T. W., Martin, R. V., van Donkelaar, A., Leaitch, W. R., Macdonald, A. M., Anlauf, K. G., Cohen, R. C., Bertram, T. H., Huey, L. G., Avery, M. A., Weinheimer, A. J., Flocke, F. M., Tarasick, D. W., Thompson, A. M., Streets, G. G., and Liu, X.: Trans-Pacific transport of reactive nitrogen and ozone to Canada during spring, Atmos. Chem. Phys., 10, 8353–8372, http://dx.doi.org/10.5194/acp-10-8353-2010doi:10.5194/acp-10-8353-2010, 2010.

Weiss-Penzias, P., Jaffe, D. A., Jaegle, L., and Liang, Q.: Influence of long-range-transported pollution on the annual and diurnal cycles of carbon monoxide and ozone at Cheeka Peak Observatory, J. Geophys. Res., 109, D23S14, doi:1029/2004JD004505, 2004.

Weiss-Penzias, P., Jaffe, D. A., Swartzendruber, P., Dennison, J. B., Chand, D., Hafner, W., and Prestbo, E.: Observations of Asian air pollution in the free troposphere at Mount Bachelor Observatory during the spring of 2004, J. Geophys. Res., 111, D24301, http://dx.doi.org/10.1029/2005JD006522doi:10.1029/2005JD006522, 2006.

Wotawa, G., Novelli, P. C., Trainer, M., and Granier, C.: Inter-annual variability of summertime CO concentrations in the Northern Hemisphere explained by boreal forest fires in North America and Russia, Geophys. Res. Lett., 28, 4575–4578, 2001.

Wotawa, G. and Trainer, M.: The influence of Canadian forest fires on pollutant concentrations in the United States, Science, 288, 324, http://dx.doi.org/10.1126/science.288.5464.324doi:10.1126/science.288.5464.324, 2000.

Yurganov, L. N., Duchatelet, P., Dzhola, A. V., Edwards, D. P., Hase, F., Kramer, I., Mahieu, E., Mellqvist, J., Notholt, J., Novelli, P. C., Rockmann, A., Scheel, H. E., Schneider, M., Schulz, A., Strandberg, A., Sussmann, R., Tanimoto, H., Velazco, V., Drummond, J. R., and Gille, J. C.: Increased Northern Hemispheric carbon monoxide burden in the troposphere in 2002 and 2003 detected from the ground and from space, Atmos. Chem. Phys., 5, 563–573, http://dx.doi.org/10.5194/acp-5-563-2005doi:10.5194/acp-5-563-2005, 2005.

Zhang, L., Jacob, D. J., Boersma, K. F., Jaffe, D. A., Olson, J. R., Bowman, K. W., Worden, J. R., Thompson, A. M., Avery, M. A., Cohen, R. C., Dibb, J. E., Flock, F. M., Fuelberg, H. E., Huey, L. G., McMillan, W. W., Singh, H. B., and Weinheimer, A. J.: Transpacific transport of ozone pollution and the effect of recent Asian emission increases on air quality in North America: an integrated analysis using satellite, aircraft, ozonesonde, and surface observations, Atmos. Chem. Phys., 8, 6117–6136, http://dx.doi.org/10.5194/acp-8-6117-2008doi:10.5194/acp-8-6117-2008, 2008.