ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-8677-2011 Anthropogenic emissions during Arctas-A: mean transport characteristics and regional case studies Harrigan D. L. 1 4 Fuelberg H. E. 1 Simpson I. J. 2 Blake D. R. 2 Carmichael G. R. 3 Diskin G. S. 5 Department of Meteorology, Florida State University, Tallahassee, FL, USA Department of Chemistry, University of California, Irvine, CA, USA Center for Global and Regional Environmental Research, University of Iowa, Iowa City, IA, USA National Oceanic and Atmospheric Administration, National Weather Service, Tallahassee, FL, USA NASA Langley Research Center, Hampton, VA, USA 25 08 2011 11 16 8677 8701 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/11/8677/2011/acp-11-8677-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/8677/2011/acp-11-8677-2011.pdf

The National Aeronautics and Space Administration (NASA) conducted the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission during 2008 as a part of the International Polar Year (IPY). The purpose of ARCTAS was to study the factors responsible for changes in the Arctic's atmospheric composition and climate. A major emphasis was to investigate Arctic haze, which is most pronounced during winter and early spring. This study focuses on the spring phase of ARCTAS (ARCTAS-A) that was based in Alaska during April 2008. Although anthropogenic emissions historically have been associated with Arctic haze, biomass burning emissions dominated the ARCTAS-A period and have been the focus of many ARCTAS related studies. <br><br> This study determines mean transport characteristics of anthropogenic emissions during ARCTAS-A. Trajectories are initiated each day from three significant regions of anthropogenic emissions (Asia, North America, and Europe). The fifteen day forward trajectories are calculated using data from the Weather Research and Forecasting (WRF) model at 45 km horizontal resolution. The trajectory calculations indicate: origins of emissions that reach the Arctic (defined as north of 70° N) within fifteen days, pathways of these emissions, Arctic entry locations, and altitudes at which the trajectories enter the Arctic. <br><br> Three cases during the ARCTAS-A period (one for each of the regions above) are examined using backward trajectories and chemical fingerprinting based on in situ data sampled from the NASA DC-8. The fingerprinting utilizes volatile organic compounds that represent pure anthropogenic tracers, Asian anthropogenic pollution, incomplete combustion, and natural gas emissions. We determine flight legs containing anthropogenic emissions and the pathways travelled by these emissions. Results show that the DC-8 sampled anthropogenic emissions from Asia, North America, and Europe during the spring phase of ARCTAS. The pathways travelled by these emissions agree with our derived transport characteristics and previous studies of Arctic transport. Meteorological analysis and trajectory calculations indicate that middle latitude cyclones and their associated warm conveyor belts play an important role in lofting the surface based emissions to their sampling altitude in all three cases.

 References Anderson, B. E., Grant, W., Gregory, G., Browell, E., Collins Jr., J., Sachse, G., Bagwell, D., Hudgins, C., Blake, D., and Blake, N.: Aerosols from biomass burning over the south tropical Atlantic region: Distributions and impacts, J. Geophys Res., 101(D19), 24117–24138, 1996. Aucott, M. L., McCulloch, A., Graedel, T. E., Kleiman, G., Midgley, P., and Li, Y.-F.: Anthropogenic emissions of trichloromethane (chloroform, CHCl$_3)$ and chlorodifluoromethane (HCFC-22): Reactive Chlorine Emissions Inventory, J. Geophys. Res., 104, 8405–8415, 1999. Barletta, B., Meinardi, S., Simpson, I. J., Atlas, E. L., Beyersdorf, A. J., Baker, A. K., Blake, N. J., Yang, M., Midyett, J. R., Novak, B. J., McKeachie, R. J., Fuelberg, H. E., Sachse, G. W., Avery, M. A., Campos, T., Weinheimer, A. J., Rowland, F. S., and Blake, D. R.: Characterization of volatile organic compounds (VOCs) in Asian and north American pollution plumes during INTEX-B: identification of specific Chinese air mass tracers, Atmos. Chem. Phys., 9, 5371–5388, http://dx.doi.org/10.5194/acp-9-5371-2009doi:10.5194/acp-9-5371-2009, 2009. Barrie, L. A. and Hoff, R. M.: Five years of air chemistry observations in the Canadian Arctic, Atmos. Environ., 19, 1995–2010, 1985. Barrie, L. A., Bottenheim, J. W., and Hart, W. R.: Polar Sunrise Experiment 1992 (PSE 1992): Preface, J. Geophys. Res., 99, 25313–25314, 1994. Blake, N. J., Blake, D.R., Sive, B.C., Chen, T-Y., Rowland, F.S., Collins, Jr., J.E., Sachse, G.W., and Anderson, B.E.: Biomass burning emissions and vertical distribution of atmospheric methyl halide and other reduced carbon gases in the South Atlantic region, J. Geophys. Res., 101(D19), 24151–24164, 1996. Blake, N. J., Blake, D. R., Simpson, I. J., Meinardi, S., Swanson, A. L., Lopez, J. P., Katzenstein, A. S., Barletta, B., Shirai, T., Atlas, E., Sachse, G., Avery, M., Vay, S., Fuelberg, H. E., Kiley, C. M., Kita, K., and Rowland, F. S.: NMHCs and halocarbons in Asian continental outflow during the Transport and Chemical Evolution over the Pacific (TRACE-P) Field Campaign: Comparison With PEM-West B, J. Geophys. Res., 108(D20), 8806, http://dx.doi.org/10.1029/2002JD003367doi:10.1029/2002JD003367, 2003. Blake, N. J., Streets, D. G., Woo, J., Simpson, I. J., Green, J., Meinardi, S., Kita, K., Atlas, E., Fuelberg, H. E., Sachse, G., Avery, M. A., Vay, S. A., Talbot, R. W., Dibb, J. E., Bandy, A. R., Thornton, D. C., Rowland, F. S., and Blake, D. R.: Carbonyl sulfide and carbon disulfide: Large-scale distributions over the western Pacific and emissions from Asia during TRACE-P, J. Geophys. Res., 109, D15S05, http://dx.doi.org/10.1029/2003JD004259doi:10.1029/2003JD004259, 2004. Blake, D.: Whole air sampling (WAS) from the DC-8 aircraft during ARCTAS, 2008, available at: http://www.espo.nasa.gov/arctas/docs/instruments/was.pdf, 2008. Bradley, R. S., Keiming, F. T., and Diaz, H. F.: Climatology of surface-based inversions in the North American Arctic, J. Geophys. Res., 97, 15699–15712, 1992. Butler, J. H., Montzka, S. A., Clarke, A. D., Lobert, J. M., and Elkins, J. W.: Growth and distribution of halons in the atmosphere, J. Geophys. Res., 103(D1), 1503–1511, 1998. Carlson, T. N.: Speculations on the movement of polluted air to the Arctic, Atmos. Environ., 15, 1473–1477, 1981. Carter, W. P. L.: Development of ozone reactivities for volatile organic compounds, JAPCA J. Air Waste Manag., 44, 881–899, 1994. Curry, J. A.: On the formation of continental polar air, J. Atmos. Sci., 40, 2279–2292, 1983. Curry, J. A.: The contribution of radiative cooling to the formation of cold-core anticyclone, J. Atmos. Sci., 44, 2575–2592, 1987. Ding, A., Wang, T., Xue, L., Gao, J., Stohl, A., Lei, H., Jin, D., Ren, Y., Wang, X., Wei, X., Qi, Y., Liu, J., and Zhang, X.: Transport of north China air pollution by midlatitude cyclones: Case study of aircraft measurements in summer 2007, J. Geophys. Res., 114, D08304, http://dx.doi.org/10.1029/2008JD011023doi:10.1029/2008JD011023, 2009. Eckhardt, S., Stohl, A., Beirle, S., Spichtinger, N., James, P., Forster, C., Junker, C., Wagner, T., Platt, U., and Jennings, S. G.: The North Atlantic Oscillation controls air pollution transport to the Arctic, Atmos. Chem. Phys., 3, 1769–1778, http://dx.doi.org/10.5194/acp-3-1769-2003doi:10.5194/acp-3-1769-2003, 2003. Eckhardt, S., Stohl, A., Wernli, H., James, P., Forster, C., and Spichtinger, N.: A 15-year climatology of warm conveyor belts, J. Climate, 17, 218–237, 2004. Fraser, P. J., Oram, D. E., Reeves, C. E., Penkett, S. A., and McCulloch, A.: Southern hemispheric halon trends (1978-1998) and global halon emissions, J. Geophys. Res., 104(D13), 15985–16000, 1999. Fuelberg, H. E., Loring, Jr., R. O., Watson, M. V., Sinha, M. C., Pickering, K. E., Thompson, A. M., Sachse, G. W., Blake, D. R., and Schoeberl, M. R.: TRACE-A trajectory intercomparison 2. Isentropic and kinematic methods, J. Geophys. Res., 101, 23927–23939, 1996. Fuelberg, H. E., Hannan, J. R., van Velthoven, P. F. J., Browell, E. V., Bieberbach, G. Jr., Knabb, R. D., Gregory, G. L., Pickering, K. E., and Selkirk, H. B.: A meteorological overview of the SONEX period, J. Geophys. Res., 105, 3633–3651, 2000. Fuelberg, H. E., Harrigan, D. L., and Sessions, W.: A meteorological overview of the ARCTAS 2008 mission, Atmos. Chem. Phys., 10, 817–842, http://dx.doi.org/10.5194/acp-10-817-2010doi:10.5194/acp-10-817-2010, 2010. Hileman, B.: Arctic Haze, Environ. Sci. Technol., 17(6), 232–236, http://dx.doi.org/10.1021/es00112a602doi:10.1021/es00112a602, 1983. Hoff, R. M.: Vertical structure of Arctic Haze observed by lidar, J. Appl. Meteor., 27, 125–139, 1987. Iverson, T.: On the atmospheric transport of pollution to the Arctic, Geophys. Res. Lett., 11, 457–460, 1984. Jacob, D. J., Crawford, J. H., Maring, H., Clarke, A. D., Dibb, J. E., Emmons, L. K., Ferrare, R. A., Hostetler, C. A., Russell, P. B., Singh, H. B., Thompson, A. M., Shaw, G. E., McCauley, E., Pederson, J. R., and Fisher, J. A.: The Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission: design, execution, and first results, Atmos. Chem. Phys., 10, 5191–5212, http://dx.doi.org/10.5194/acp-10-5191-2010doi:10.5194/acp-10-5191-2010, 2010. Kasischke, E. S., Hyer, E. J., Novelli, P. C., Bruhwiler, L. P., French, N. H. F., Sukhinin, A. I., Hewson, J. H., and Stocks, B. J.: Influences of boreal fire emissions on Northern Hemisphere atmospheric carbon and carbon monoxide, Global Biogeochem. Cy., 19, GB1012, http://dx.doi.org/10.1029/2004GB002300doi:10.1029/2004GB002300, 2005. Katzenstein, A. S., Doezema, L. A., Simpson, I. J., Blake, D. R., and Rowland, F. S.: Extensive regional atmospheric hydrocarbon pollution in the southwestern United States, Proc. Nat. Acad. Sciences, 100, 11, 975–11, 979, 2003. Kettle, A. J., Kuhn, U., von Hobe, M., Kesselmeier, J., and Andreae, M. O.: Global budget of carbonyl sulfide: Temporal and spatial variations of the dominant sources and sinks, J. Geophys. Res., 107(D22), 4658, http://dx.doi.org/10.1029/2002JD002187doi:10.1029/2002JD002187, 2002. Klonecki, A., Hess, P., Emmons, L., Smith, L., and Orlando, J.: Seasonal changes in the transport of pollutants into the Arctic troposphere-model study, J. Geophys. Res., 8367, doi:1029/2002JD002199, 2003. Kondo, Y., Sahu, L., Moteki, N., Takegawa, N., Matsui, H., Zhao, Y., Vay, S., Diskin, G. S., Anderson, B., Wisthaler, A., Jimenez, J. L., Fuelberg, H. E., Huey, G., Weinheimer, A. J., and Brune, W. H.: Emissions of black carbon and organic aerosols from forest fires in Canada and Russia in 2008, J. Geophys. Res., 116, D08204, http://dx.doi.org/10.1029/2010JD015152doi:10.1029/2010JD015152, 2011. Law, K. S. and Stohl, A.: Arctic air pollution: Origins and impacts, Science, 315, 1537–1540, http://dx.doi.org/10.1126/science.1137695doi:10.1126/science.1137695, 2007. Lee, B. H., Munger, J. W., Wofsy, S. C., and Goldstein, A. H.: Anthropogenic emissions of nonmethane hydrocarbons in the northeastern United States: Measured seasonal variations from 1992–1996 and 1999–2001, J. Geophys. Res., 111, D20307, http://dx.doi.org/10.1029/2005JD006172doi:10.1029/2005JD006172, 2006. Li, S. M. and Barrie, L. A.: Biogenic sulphur aerosols in the Arctic troposphere, 1. Contributions to sulphate, J. Geophys. Res., 98(D11), 20613–20622, 1993. Martin, B. D., Fuelberg, H. E., Blake, N. J., Crawford, J. H., Logan, J. A., Blake, D. R., and Sachse, G. W.: Long range transport of Asian outflow to the equatorial Pacific, J. Geophys. Res., 108(D2), 8322, http://dx.doi.org/10.1029/2001JD001418doi:10.1029/2001JD001418, 2002. Matsui, H., Kondo, Y., Moteki, N., Takegawa, N., Sahu, L. K., Zhao, Y., Fuelberg, H. E., Sessions, W., Diskin, G., Blake, D. R., and Wisthaler, A.: Seasonal variation of the transport of black carbon aerosol from the Asian continent to the Arctic during the ARCTAS aircraft campaign, J. Geophys. Res., 116, D05202, http://dx.doi.org/10.1029/2010JD015067doi:10.1029/2010JD015067, 2011. Meyer, F. G., Curry, J. A., Brock, C. A., and Radke, L. F.: Springtime visibility in the Arctic, J. Appl. Meteor., 30, 342–357, 1990. Mitchell, J. M. Jr.: Visual range in the polar regions with particular reference to the Alaskan Arctic, J. Clim. Appl. Meteor., 23, 916–928, 1957. Montzka, S. A., Hall, B. D., and Elkins, J. A.: Accelerated increases observed for hydrochlorofluorocarbons since 2004 in the global atmosphere, Geophys. Res. Lett., 36, L03804, http://dx.doi.org/10.1029/2008GL036475doi:10.1029/2008GL036475, 2009. Oltmans, S. J., Lefohn, A. S., Harris, J. M., Tarasick, D. W., Thompson, A. M., Wernli, H., Johnson, B. J., Davies, J., Novelli, P. C., Montzka, S. A., Sweeney, C., Patrick, L. A., Jefferson, A., Dann, T., Ray, J. D., and Shapiro, M.: Enhanced ozone over western North America from biomass burning in Eurasia during April 2008 as seen in surface and profile observations,, Atmos. Environ., 44, 35, 4497–4509, http://dx.doi.org/10.1016/j.atmosenv.2010.07.004doi:10.1016/j.atmosenv.2010.07.004, 2010. Quinn, P. K., Miller, T. L., Bates, T. S., Ogren, J. A., Andrews, E., and Shaw, G. E.: A three-year record of simultaneously measured aerosol chemical and optical properties at Barrow, Alaska. J. Geophys. Res., 107(D11), http://dx.doi.org/10.1029/2001JD001248doi:10.1029/2001JD001248, 2002. Raatz, W. E. and Shaw, G. E.: Long-range tropospheric transport of pollution aerosols in the Alaskan Arctic, J. Clim. Appl. Meteor., 23, 1052–1064, 1984. Raatz, W. E.: The climatology and meteorology of Arctic air pollution, in: Pollution of the Arctic Atmosphere, edited by: Sturges, W. T., Elsevier, New York, 13–42, 1991. Reid, J., Hyer, E. J., Prins, E. M., Westphal, D. L., Zhang, J., Wang, J., Christopher, S. A., Curtis, C. A., Schmidt, C. A., Eleuterio, D. P., Richardson, K. A., and Hoffman, J. P.: Global Monitoring and Forecasting of Biomass Burning Smoke: Description of and Lessons From the Fire Locating and Modeling of Burning Emissions (FLAMBE) Program, IEEE J. Sel. Top. Appl., 2, 2009. Rinke, A., Dethloff, K., and Fortmann, M.: Regional climate effects of Arctic Haze, Geophys. Res. Lett., 31, L16202, http://dx.doi.org/10.1029/2004GL020318doi:10.1029/2004GL020318, 2004. Russo, R., Talbot, R. W., Dibb, J. E., Scheuer, E., Seid, G., Jordan, C. E., Fuelberg, H. E., Sachse, G. W., Avery, M. A., Vay, S. A., Blake, D. R., Blake, N. J., Atlas, E., Fried, A., Sandholm, S. T., Tan, D., Singh, H. B., Snow, J., and Heikes, B. G.: Chemical composition of Asian continental outflow over the western Pacific: Results from Transport and Chemical Evolution over the Pacific (TRACE-P), J. Geophys. Res., 108(D20), 8804, http://dx.doi.org/10.1029/2002JD003184doi:10.1029/2002JD003184, 2003. Russo, R. S., Zhou, Y., White, M. L., Mao, H., Talbot, R., and Sive, B. C.: Multi-year (2004–2008) record of nonmethane hydrocarbons and halocarbons in New England: seasonal variations and regional sources, Atmos. Chem. Phys., 10, 4909–4929, http://dx.doi.org/10.5194/acp-10-4909-2010doi:10.5194/acp-10-4909-2010, 2010. Sachse, G. W., Hill, G. F., Wade, L. O., and Perry, M. G.: Fastresponse, highprecision carbon monoxide sensor using a tunable diode laser absorption technique, J. Geophys. Res., 92, 2071–2081, 1987. Sachse, G. W., Harriss, R. C., Fishman, J., Hill, G.F., and Cahoon, D.R.: Carbon monoxide over the Amazon basin during the 1985 dry season, J. Geophys. Res., 93, 1422–1430, 1988. Schnell, R. C.: Arctic haze and the Arctic gas aerosol sampling program (AGASP), Geophys. Res. Lett., 11, 361–364, 1984. Shaw, G. E.: Evidence for a central Eurasian source area of Arctic haze in Alaska, Nature, 299, 815–818, 1983. Shaw, G. E.: The Arctic haze phenomenon, B. Am. Meteor. Soc., 76, 2403–2413, 1995. Simpson, I. J., Meinardi, S., Blake, N. J., Rowland, F. S., and Blake, D. R.: Long-term decrease in the global atmospheric burden of tetrachloroethene (C<sub>2</sub>Cl$_4)$, Geophys. Res. Lett., http://dx.doi.org/10.1029/2003GL019351doi:10.1029/2003GL019351, 2004. Simpson, I. J., Blake, N. J., Barletta, B., Diskin, G. S., Fuelberg, H. E., Gorham, K., Huey, L. G., Meinardi, S., Rowland, F. S., Vay, S. A., Weinheimer, A. J., Yang, M., and Blake, D. R.: Characterization of trace gases measured over Alberta oil sands mining operations: 76 speciated C<sub>2</sub>-C$_10$ volatile organic compounds (VOCs), CO<sub>2</sub>, CH<sub>4</sub>, CO, NO, NO<sub>2</sub>, NO$_y$, O<sub>3</sub> and SO<sub>2</sub>, Atmos. Chem. Phys., 10, 11931–11954, http://dx.doi.org/10.5194/acp-10-11931-2010doi:10.5194/acp-10-11931-2010, 2010. Singh, H. B., Anderson, B. E., Brune, W. H., Cai, C., Crawford, J. H., Cohen, R. C., Czech, E. P., Emmons, L., Fuelberg, H. E., Huey, G., Jacob, D. J., Jimenez, J. L., Kondo, Y., Kaduwela, A., Mao, J., Olson, J. R., Sachse, G. W., Vay, S. A., Weinheimer, A., Wennberg, P. O., and Wisthaler, A.: Pollution influences on atmospheric composition and chemistry at high northern latitudes: Boreal and California forest fire emissions, Atmos. Environ., 44, 4553–4564, 2010. Skamarock, W. C., Klemp, J. B., Dudhia, J., Gill, D. O. Barker, D. M., Duda, M. G., Huang, X., Wang, W., and Powers, J. G.: A description of the Advanced Research WRF version 3. NCAR Tech. Note NCAR/TN-475+STR, 113 pp., 2008. Stohl, A.: A 1-year Lagrangian "climatology" of airstreams in the Northern Hemisphere troposphere and lowermost stratosphere, J. Geophys. Res., 106(D7), 7263–7279, 2001. Stohl, A.: Characteristics of atmospheric transport into the Arctic troposphere, J. Geophys Res., D11306, doi:1029/2005JD006888, 2006. Stohl, A., Wotawa, G., Seibert, P., and Kromp-Kolb, H.: Interpolation errors in wind fields as a function of spatial and temporal resolution and their impact on different types of kinematic trajectories, J. Appl. Meteor., 34, 2149–2165, 1995. Stohl, A., Hittenberger, M., and Wotawa, B.: Validation of the Lagrangian particle dispersion model FLEXPART against large scale tracer experiments, Atmos. Environ., 32, 4245–4264, 1998. Stohl, A., Forster, C., Frank, A., Seibert, P., and Wotawa, G.: Technical note: The Lagrangian particle dispersion model FLEXPART version 6.2, Atmos. Chem. Phys., 5, 2461–2474, http://dx.doi.org/10.5194/acp-5-2461-2005doi:10.5194/acp-5-2461-2005, 2005. Stohl, A., Eckhardt, S., Forster, C., James, P., and Spichtinger, N.: On the pathways and timescales of intercontinental air pollution transport, J. Geophys. Res. 107(D23), 4684, http://dx.doi.org/10.1029/2001JD001396doi:10.1029/2001JD001396, 2002. Streets, D. G., Bond, T. C., Carmichael, G. R., Fernandes, S. D., Fu, Q., He, D., Klimont, Z., Nelson, S. M., Tsai, N. Y., Wang, M. Q., Woo, J. H., and Yarber, K. F.: An inventory of gaseous and primary aerosol emissions in Asia in the year 2000, J. Geophys. Res., 108(D21), 8809, http://dx.doi.org/10.1029/2002JD003093doi:10.1029/2002JD003093, 2003. Warneke, C., Bahreini, R., Brioude, J., Brock, C. A., de Gouw, J. A., Fahey, D. W., Froyd, K. D., Holloway, J. S., Middlebrook, A., Miller, L., Montzka, S., Murphy, D. M., Peischl, J., Ryerson, T. B., Schwarz, J. P., Spackman, J. R., and Veres, P.: Biomass burning in Siberia and Kazakhstan as an important source for haze over the Alaskan Arctic in April 2008, Geophys. Res. Lett., 36, L02813, http://dx.doi.org/10.1029/2008GL036194doi:10.1029/2008GL036194, 2009. Warneke, C., McKeen, S. A., de Gouw, J. A., Goldan, P. D., Kuster, W. C., Holloway, J. S., Williams, E. J., Lerner, B. M., Parrish, D. D., Trainer, M., Fehsenfeld, F. C., Kato, S., Atlas, E. L., Baker, A., and Blake, D. R.: Determination of urban volatile organic compound emission ratios and comparison with an emissions database, J. Geophys. Res., 112, D10S47, http://dx.doi.org/10.1029/2006JD007930doi:10.1029/2006JD007930, 2007. Warneke, C., Froyd, K. D., Brioude, J., Bahreini, R., Brock, C. A., Cozic, J., de Gouw, J. A., Fahey, D. W., Ferrare, R., Holloway, J. S., Middlebrook, A. M., Miller, L., Montzka, S., Schwarz, J. P., Sodemann, H., Spackman, J. R., and Stohl, A.: An important contribution to springtime Arctic aerosol from biomass burning in Russia, Geophys. Res. Lett., 37, L01801, http://dx.doi.org/10.1029/2009GL041816doi:10.1029/2009GL041816, 2010. Watts, S. F.: The mass budget of carbonyl sulfide, dimethyl sulfide, carbon disulfide, and hydrogen sulfide, Atmos. Environ., 34, 761–779, 2000. Wotton, B. M., Nock, C. A., and Flannigan, M. D., Forest fire occurrence and climate change in Canada, Intl. J. Wildland Fire, 19 (3), 253–271, 2010. Xiao, Y., Logan, J. A., Jacob, D. J., Hudman, R. C., Yantosca, R., and Blake, D. R.: Global budget of ethane and regional constraints on US sources, J. Geophys. Res., 113, D21306, http://dx.doi.org/10.1029/2007JD009415doi:10.1029/2007JD009415, 2008.