Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 9 3 2009 10.5194/acpd-9-11185-2009 http://www.atmos-chem-phys-discuss.net/9/11185/2009/ http://www.atmos-chem-phys-discuss.net/9/11185/2009/acpd-9-11185-2009.html http://www.atmos-chem-phys-discuss.net/9/11185/2009/acpd-9-11185-2009.pdf 11185 11220 2009-05-05 Quantifying atmospheric nitrate formation pathways based on a global model of the oxygen isotopic composition (Δ¹⁷O) of atmospheric nitrate B. Alexander beckya@u.washington.edu M. G. Hastings D. J. Allman J. Dachs J. A. Thornton S. A. Kunasek Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA Department of Geological Sciences and Environmental Change Initiative, Brown University, Providence, RI, USA Department of Environmental Chemistry, Instituto de Investigaciones Químicas y Ambientales de Barcelona/Consejo Superior de Investigaciones Científicas, Barcelona, Spain Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA The oxygen isotopic composition (Δ¹⁷O) of atmospheric nitrate is a function of the relative abundance of atmospheric oxidants (O₃, HO_x=OH +HO₂+RO₂) and the formation pathway of nitrate from its precursor NO_x (=NO+NO₂). Coupled observations and modeling of nitrate Δ¹⁷O can be used to quantify the relative importance of chemical formation pathways leading to nitrate formation and reduce uncertainties in the budget of reactive nitrogen chemistry in the atmosphere. We present the first global model of atmospheric nitrate Δ¹⁷O and compare with available observations. The model shows the best agreement with a global compilation of observations when assuming a Δ¹⁷O value of tropospheric ozone equal to 35‰ and preferential oxidation of NO_x by the terminal oxygen atoms of ozone. Calculated values of annual-mean nitrate Δ¹⁷O in the lowest model layer (0–200 m above the surface) vary from 6‰ in the tropics to 41‰ in the polar-regions. On the global scale, O₃ is the dominant oxidant (81% annual-mean) during NO_x cycling reactions. The global, annual-mean tropospheric inorganic nitrate burden is dominated by nitrate formation via NO₂+OH (76%), followed by N₂O₅ hydrolysis (18%) and NO₃+DMS/HC (4%). Model discrepancies are largest in the polar spring and summer, most likely due to the lack of reactive halogen chemistry in the model. The influence of organic nitrates on observations of nitrate Δ¹⁷O needs to be determined, especially for observations in summertime and tropical forested regions where organic nitrates can contribute up to 80% of the total NO_y (organic plus inorganic nitrate) budget. Alexander, B., Savarino, J., Kreutz, K J., and Thiemens, M H.: Impact of preindustrial biomass-burning emissions on the oxidation pathways of tropospheric sulfur and nitrogen, J. Geophys. Res., 109, D08303, doi:10.1029/2003JD004218, 2004. Alexander, B., Savarino, J., Lee, C C W., Park, R J., Jacob, D J., Li, Q., Yantosca, R M., and Thiemens, M H.: Sulfate formation in sea-salt aerosols: Constraints from oxygen isotopes, J. Geophys. Res., 110, D10307, doi:10.1029/2004JD005659, 2005. Benkovitz, C M., Schultz, M T., Pacyna, J., Tarrason, L., Dignon, J., Voldner, E C., Spiro, P A., Logan, J A., and Graedel, T E.: Global, gridded inventories for anthropogenic emissions of sulfur and nitrogen, J. Geophys. Res., 101, 29239–29253, 1996. Bey, I., Jacob, D J., Yantosca, R M., Logan, J A., Field, B D., Fiore, A M., Li, Q., Liu, H Y., Mickley, L J., and Schultz, M G.: Global modeling of tropospheric chemistry with assimilated meteorology: Model description and evaluation, J. Geophys. Res., 106, 23073–23095, 2001. Bhattacharya, S K., Pandey, A., and Savarino, J.: Determination of intramolecular isotope distribution of ozone by oxidation reaction with silver metal, J. Geophys. Res., 113, D03303, doi:10.1029/2006JF008309, 2008. Bohlke, J K., Mroczkowski, S J., and Coplen, T B.: Oxygen isotopes in nitrate: new reference materials for O-18:O-17:O-16 measurements and observations on nitrate-water equilibration, Rapid Commun. Mass. Sp., 17, 1835–1846, 2003. Brothers, L A., Dominguez, G., Fabian, P., and Thiemens, M H.: Using multi-isotope tracer methods to understand the sources of nitrate in aerosols, fog and river water in Podocarpus National Forest, Ecuador, Eos Trans. AGU, 89, Abstract A11C-0136, 2008. Casciotti, K L., Sigman, D M., Hastings, M G., Bohlke, K K., and Hilkert, A.: Measurement of the oxygen isotopic composition of nitrate in seawater and freshwater using the denitrifier method, Anal. Chem., 74, 4905–4912, 2002. Chance, K.: Analysis of \chemBrO Measurements from the global ozone monitoring experiment, Geophys. Res. Lett., 25, 3335–3338, 1998. Dachs, J., Calleja, M L., Duarte, C M., Vento, S D., Turpin, B., Polisori, A., Herndl, G J., and Agusti, S.: High atmosphere-ocean exchange of organic carbon in the NE subtropical Atlantic, Geophys. Res. Lett., 32, L21807, doi:10.1029/2005GL023799, 2005. Davis, J M., Bhave, P V., and Foley, K M.: Parameterization of \chemN_2O_5 reaction probabilities on the surface of particles containing ammonium, sulfate, and nitrate, Atmos. Chem. Phys., 8, 5295–5311, 2008. DeMore, B W., Sander, S P., Golden, D M., Hampson, R F., Kurylo, M J., Howard, C J., Ravishankara, A R., Kolb, C E., and Molina, M J.: Chemical kinetics and photochemical data for use in stratospheric modeling, JPL Publ., 97-4, 1–278, 1997. Dentener, F J. and Crutzen, P J.: Reaction of \chemN_2O_5 on tropospheric aerosols: Impact on the global distributions of \chemNO_x, \chemO_3, and \chemOH, J. Geophys. Res., 98, 7149–7163, 1993. Duarte, C M., Dachs, J., Llabres, M., Alonso-Laita, P., Gasol, J M., Tovar-Sanchez, A., Sanudo-Wilhemy, S., and Agusti, S.: Aerosol inputs enhance new production in the subtropical northeast Atlantic, J. Geophys. Res., 111, G04006, doi:10.1029/2005JG000140, 2006. Dubey, M K., Mohrschladt, R., Donahue, N M., and Anderson, J G.: Isotope-specific kinetics of hydroxyl radical (\chemOH) with water (\chemH_2O): Testing models of reactivity and atmospheric fractionation, J. Phys. Chem. A., 101, 1494–1500, 1997. Evans, M J., Jacob, D J., Atlas, E., Cantrell, C A., Eisele, F., Flocke, F., Fried, A., Mauldin, R L., Ridley, B A., Wert, B., Talbot, R., Blake, D., Heikes, B., Snow, J., Walega, J., Weinheimer, A J., and Dibb, J.: Coupled evolution of \chemBrO_x-\chemClO_x-HO_x-NO_x chemistry during bromine-catalyzed ozone depletion events in the arctic boundary layer, J. Geophys. Res., 108, 8368, doi:10.1029/2002JD002732, 2003. Evans, M J. and Jacob, D J.: Impact of new laboratory studies of \chemN_2O_5 hydrolysis on global model budgets of tropospheric nitrogen oxides, ozone, and \chemOH, Geophys. Res. Lett., 32, L09813, doi:10.1029/2005GL022469, 2005. Ewing S A., Michalski, G., Thiemens, M., Quinn, R C., Macalady, J L., Kohl, S., Wankel, S D., Kendall, C., McKay, C P., and Amundson R.: Rainfall limit of the \chemN cycle on Earth, Global Biogeochem. Cy., 21, GB3009, doi:10.1029/2006GB002838, 2007. Fiore, A M., Jacob, D J., Bey, I., Yantosca, R M., Field, B D., and Wilkinson, J G.: Background ozone over the United States in summer: Origin and contribution to pollution episodes, J. Geophys. Res., 107, 4275, doi:10.1029/2001JD000982, 2002. Fountoukis, C. and Nenes, A.: ISORROPIA II: a computationally efficient thermodynamic equilibrium model for \chemK^+-\chemCa^2+-\chemMg^2+-\chemNH_4^+-\chemNa^+-\chemSO_4^2-\chemNO_3^-\chemCl^-\chemH_2O aerosols, Atmos. Chem. Phys., 7, 4639–4659, 2007. Franz, P. and Röckmann, T.: High-precision isotope measurements of \chemH_2^16O, \chemH_2^17O, \chemH_2^18O, and the $\Delta^17\chemO$-anomaly of water vapor in the southern lowermost stratosphere, Atmos. Chem. Phys., 5, 2949–2959, 2005. Galloway, N J., Townsend, R A., Erisman, W J., Bekunda, M., Cai, Z., Freney, R J., Martinelli, L A., Seitzinger, S P., and Sutton, M A.: Transformation of the nitrogen cycle: Recent trends, questions, and potential solutions, Science, 320, 889–892, doi:10.1126/science.1136674, 2008. Gerber, H E.: Relative-humidity paramaterization of the Nave aerosol model (NAM), Natl. Res. Lab., Washington, D.C., 1985. Grannas, A M., Jones, A E., Dibb, J., Ammann, M., Anastasio, C., Beine, H J., Bergin, M., Bottenheim, J., Boxe, C S., Carver, G., Chen, G., Crawford, J H., Dominé, F., Frey, M M., Guzmán, M I., Heard, D E., Helmig, D., Hoffmann, M R., Honrath, R E., Huey, L G., Hutterli, M., Jacobi, H W., Klán, P., Lefer, B., McConnell, J., Plane, J., Sander, R., Savarino, J., Shepson, P B., Simpson, W R., Sodeau, J R., von Glasow, R., Weller, R., Wolff, E W., and Zhu, T.: An overview of snow photochemistry: evidence, mechanisms and impacts, Atmos. Chem. Phys., 7, 4329–4373, 2007. Guenther, A., Hewitt, N C., Erickson, D., Fall, R., Geron, C., Graedel, T., Harley, P., Klinger, L., Lerdau, M., McKay, W A., Pierce, T., Scholes, B., Steinbrecher, R., Tallamraju, R., Taylor, J., Zimmerman, P.: A~global model of natural volatile organic compound emissions, J. Geophys. Res., 100, 8873–8892, 1995. Guenther, A., Karl, T., Harley, P., Wiedinmyer, C., Palmer, P I., and Geron, C.: Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature), Atmos. Chem. Phys., 6, 3181–3210, 2006. Hallquist, M., Stewart, D J., Stephenson, S K., and Cox, R A.: Hydrolysis of \chemN_2O_5 on sub-micron sulfate aerosol, Phys. Chem. Chem. Phys., 5, 3453–3463, 2003. Hastings, M G. and Sigman, D M.: Isotopic evidence for source changes of nitrate in rain at Bermuda, J. Geophys. Res., 108(D24), 4790, doi:10.1029/2003JD003789, 2003. Hauff, K., Fischer, R G., and Ballschmiter, K.: Determination of C1-C5 alkyl nitrates in rain, snow, white frost, lake, and tap water by a~combined codistillation head-space gas chromatography technique. Determination of henry's law constants by head-space GC, Chemosphere, 37, 2599–2615, 1998. Honrath, E R., Lu, Y., Peterson, C M., Dibb, E J., Arsenault, A M., Cullen, J N., and Steffen, K.: Vertical fluxes of NO_x, \chemHONO, and \chemHNO_3 above the snowpack at Summit, Greenland, Atmos. Environ., 36, 2629–2640, 2002. Hudman, R C., Murray, L T., Jacob, D J., Turquety, S., Wu, S., Millet, D B., Avery, M., Goldstein, A H., and Holloway, J.: North American influence on tropospheric ozone and the effects of recent emission reductions: Constraints from ICARTT observations, J. Geophys. Res, 114, D07302, doi:10.1029/2008JD010126, 2009. Huey, L G., Dibb, J., Stutz, J., Brooks, S., von Glasow, R., Lefer, B., Chen, G., Kim, S., and Tanner, D.: Observations of halogens at Summit, Greenland, EOS Transactions, AGU, 88, Fall Meet. Suppl., Abstract A42B-05, 2007. Jacob, D J.: Heterogeneous chemistry and tropospheric ozone, Atmos. Env., 34, 2131–2159, 2000. Jaegle, L., Steinberger, L., Martin, R V., and Chance, K.: GLobal partitioning of NO_x sources using satellite observations: Relative roles of fossil fuel combustion, biomass burning and soil emissions, Faraday Discuss., 130, 407–423, doi:10.1039/b502128f, 2005. Janssen, C., Guenther, J., and Krankowsky, D.: Relative formation rates of $^50\chemO_3$ and $^52\chemO_3$ in $^16\chemO^-$ $^18\chemO$ mixtures, J. Chem. Phys., 111, 7179–7182, 1999. Janssen, C.: Intramolecular isotope distribution in heavy ozone ($^16\chemO ^18\chemO ^16\chemO$ and $^16\chemO ^16\chemO ^18\chemO$), J. Geophys. Res, 110, D08308, doi:10.1029/2004JD005479, 2005. Johnston, J C. and Thiemens, M H.: The isotopic composition of tropospheric ozone in three environments, J. Geophys. Res., 102, 25395–25404, 1997. Jones, A E., Weller, R., Wolff, E W., and Jacobi, A H.-W.: Speciation and rate of photochemical \chemNO and \chemNO_2 production in Antarctic snow, Geophys. Res. Lett., 27, 345–348, 2000. Kaiser, J., Hastings, M G., Houlton, B Z., Rockmann, T., and Sigman, D M.: Triple Oxygen Isotope Analysis of Nitrate Using the Denitrifier Method and Thermal Decomposition of \chemN_2O, Anal. Chem., 79, 599–607, 2007. Kane, S M., Caloz, F., and Leu, M T.: Heterogeneous uptake of gaseous \chemN_2O_5 by \chem(NH_4)_2SO_4, \chemNH_4HSO_4 and \chemH_2SO_4 aerosol, J. Phys. Chem., 105, 6465–6570, 2001. Krankowsky, D., Bartecki, F., Klees, G G., Mauersberger, K., Schellenback, K., and Stehr, J.: Measurement of heavy isotope enrichment in tropospheric ozone, Geophys. Res. Lett., 22, 1713–1716, 1995. Kreher, K., Johnson, P V., Wood, S W., Nardi, B., and Platt, U.: Ground-based measurements of tropspheric and stratospheric \chemBrO at Arrivals Heights, Antarctica, Geophys. Res. Lett., 24, 3021–3024, 1997. Kunasek, A S., Alexander, B., Hastings, M G., Steig, E J., Gleason, D J., and Jarvis, J C.: Measurements and modeling of $\Delta ^17$O of nitrate in a~snowpit from Summit, Greenland, J. Geophys. Res., 113, D24302, doi:10.1029/2008JD010103, 2008. Legrand, M R. and Kirchner, S.: Origins and variations of nitrate in south polar precipitation, J. Geophys. Res, 95, 3493–3507, 1990. Levy, H., Moxim, W J., Klonecki, A A., and Kasibhatla, P S.: Simulated tropospheric NO_x: Its evaluation, global distribution and individual source contributions, J. Geophys. Res., 104, 26279–26306, 1999. Liang, M.-C., Irion, F W., Weibel, J D., Miller, C E., Blake, G A., and Yung, Y L.: Isotopic composition of stratospheric ozone, J. Geophys. Res., 111, D02302, doi:10.1029/2005JD006342, 2006. Liu, H., Jacob, D J., Bey, I., and Yantosca, R M.: Constraints from $^210\chemPb$ and $^7\chemBe$ on wet deposition and transport in a~global three-dimensional chemical tracer model driven by assimilated meterological fields, J. Geophys. Res., 106, 12109–12128, 2001. Logan, J A.: Nitrogen oxides in the troposphere: Global and regional budgets, J. Geophys. Res.-Oc. Atm., 88, 785–807, 1983. Lyons, J R.: Transfer of mass-independent fractioation on ozone to other oxygen-containing molecules in the atmosphere, Geophys. Res. Lett., 28, 3231–3234, 2001. Martin, R V., Jacob, D. J., Loganand, J. A., et al.: Interpretation of TOMS observations of tropical tropspheric ozone with a~global model and in-situ observations, J. Geophys. Res., 107, 4351, doi:10.1029/2001JD001480, 2002. Martin, R V., Jacob, D J., Yantosca, R M., Chin, M., and Ginoux, P.: Global and regional decreases in tropospheric oxidants form photochemical effects of aerosols, J. Geophys. Res., 108, 4097, doi:4010.1029/2002JD002622, 2003. Matsuhisa, Y., Goldsmith, J R., and Clayton, R N.: Mechanisms of hydrothermal crystallization of quartz at 250°C and 15 \unitkbar, Geochim. Cosmochim. Acta, 42, 173–182, 1978. Mauersberger, K., Erbacher, B., Krankowsky, D., Gunther, J., and Nickel, R.: Ozone isotope enrichment: Isotopomer-specific rate coefficients, Science, 283, 370–372, 1999. Mauersberger, K., Lämmerzahl, P., and Krankowsky, D.: Stratospheric ozone isotope enrichments–revisited, Geophys. Res. Lett., 28, 3155–3158, 2001. Mayewski, P A., Lyons, W B., Spencer, M J., Twickler, M S., Buck, C F., and Whitlow, S.: An ice-core record of atmospheric response to anthropogenic sulphate and nitrate, Nature, 346, 554–556, 1990. McCabe, J R., Thiemens, M H., and Savarino, J.: A~record of ozone variability in South Pole Antarctic snow: Role of nitrate oxygen isotopes, J. Geophys. Res, 112, D12303, doi:10.1029/2006JD007822, 2007. McMorrow, A., Ommen, T D V., Morgan, V., and Curran, M A J.: Ultra-high-resolution seasonality of trace-ion species and oxygen isotope ratios in Antarctic firn over four annual cycles, Ann. Glaciology, 39, 34–40, 2004. McNeill, V F., Patterson, J., Wolfe, G. M., and Thornton, J.: The Effect of Varying levels of Surfactant on the Reactive Uptake of \chemN_2O_5 to Submicron Aqueous Aerosol, Atmos. Chem. Phys., 6, 1635–1644, 2006. Michalski, G M., Savarino, J., Bohlke, J K., and Thiemens, M H.: Determination of the total oxygen isotopic composition of nitrate and the calibration of a $\Delta^17\chemO$ nitrate reference material, Anal. Chem., 74, 4989–4993, 2002. Michalski, G M., Scott, Z., Kabiling, M., and Thiemens, M H.: First measurements and modeling of $\Delta^17\chemO$ in atmospheric nitrate, Geophys. Res. Lett., 30, 1870, doi:1810.1029/2003GL017015, 2003. Michalski, G. and Bhattacharya, S K.: The role of symmetry in the mass independent isotope effect in ozone, Proc. Natl. Acad. Sci., 106, 5493–5496, 2009. Millet, D B., Jacob, D J., Boersma, K F., Fu, T.-M., Kurosu, T P., Chance, K., Heald, C L., and Guenther, A.: Spatial distribution of isoprene emissions from North America derived from formaldehyde column measurements by the OMI satellite sensor, J. Geophys. Res., 113(D2), D02307, doi:10.1029/2007JD008950, 2008. Morin, S., Savarino, J., Bekki, S., Gong, S., and Bottenheim, J W.: Signature of Arctic surface ozone depletion events in the isotope anomaly ($\Delta^17\chemO$) of atmospheric nitrate, Atmos. Chem. Phys., 7, 1451–1469, 2007. Morin, S., Savarino, J., Frey, M M., Yan, N., Bekki, S., Bottenheim, J W., and Martins, J M F.: Tracing the Origin and Fate of NO_x in the Arctic Atmosphere Using Stable Isotopes in Nitrate, Science, 322, 730–732, doi:10.1126/science.1161910, 2008. Morton, J., Barnes, J., Schueler, B., and Mauersberger, K.: Laboratory studies of heavy ozone, J. Geophys. Res., 95, 901–907, 1990. Mulvaney, R. and Wolff, E W.: Evidence for winter/spring denitrification of the stratosphere in the nitrate record of antarctic firn cores, J. Geophys. Res., 98, 5213–5220, 1993. Palmer, P I., Abbot, D S., Fu, T.-Z., Jacob, D J., Chance, K., Kuruso, T P., Guenther, A., Wiedinmyer, C., Stanton, J C., Pilling, M J., Pressley, S N., Lamb, B., and Sumner, A L.: Quantifying the seasonal and interannual variability of North American isoprene emissions using satellite observations of formaldehyde column, J. Geophys. Res., 111(D12), D12315, doi:10.1029/2005JD006689, 2006. Park, R J., Jacob, D J., Field, B D., Yantosca, R M., and Chin, M.: Natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosols in the United States: implications for policy, J. Geophys. Res., 109, D15204, doi:10.1029/2003JD004473, 2004. Peterson, M C. and Honrath, R E.: Observations of Rapid Photochemical Destruction of Ozone in Snowpack Interstitial Air, Geophys. Res. Lett., 28, 511–514, 2001. Pickering, K E., Wang, Y S., Tao, W K., Price, C., and Muller, J F.: Vertical distributions of lightning \chemNO_x for use in regional and global chemical transport models, J. Geophys. Res, 103, 31203–231216, 1998. Price, C. and Rind, D.: A~simple lightning parameterization for calculating global lightning distribution, J. Geophys. Res., 97, 9919–9933, 1992. Global Fire EMissions Database, Version 2 (GFEDv2.1). Data set. Available on line., 2007. Richter, A., Wittrock, F., Eisinger, M., and Burrows, J P.: GOME observations of tropospheric \chemBrO in northern hemispheric spring and summer 1997, Geophys. Res. Lett., 25, 2683–2686, 1997. Saiz-Lopez, A., Plane, J M C., Mahajan, A S., Anderson, P S., Barguitte, S J.-B., Jones, A E., Roscoe, H K., Salmon, R A., Bloss, W J., Lee, J D., and Heard, D E.: On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for \chemO_3, \chemHO_x, \chemNO_x and the \chemHg lifetime, Atmos. Chem. Phys., 8, 887–900, 2008. Sander, S P., Friedl, R R., Ravishankara, A R., Golden, D M., Kolb, C E., Kurylo, M J., Huie, R E., Orkin, V L., Molina, M J., Moortgat, G K., and Finlayson-Pitts, B J.: Chemical Kinetics and Photochemical Data for use in Atmospheric Studies, NASA Jet Propulsion Lab, 2–25, 2000. Savarino, J., Kaiser, J., Morin, S., Sigman, D M., and Thiemens, M H.: Nitrogen and oxygen isotopic constraints on the origin of atmospheric nitrate in coastal Antarctica, Atmos. Chem. Phys., 7, 1925–1945, 2007. Savarino, J. and Thiemens, M H.: Mass-independent oxygen isotope ($^16\chemO$, $^17\chemO$, $^18\chemO$) fractionation found in \chemH_x, \chemO_x reactions, J. Phys. Chem., 103, 9221–9229, 1999a. Savarino, J. and Thiemens, M H.: Analytical procedure to determine both $\delta^18\chemO$ and $\delta^17\chemO$ of \chemH_2O_2 in natural water and first measurements, Atmos. Env., 33, 3683–3690, 1999b. Savarino, J., Bhattacharya, S K., Morin, S., Baroni, M., and Doussin, J.-F.: The $\chemNO+\chemO_3$ reaction: A~triple oxygen isotope perspective on the reaction dynamics and atmospheric implications for the transfer of the ozone isotope anomaly, J. Chem. Phys., 128, 2008. Schneider, H R., Jones, D B A., McElroy, M B., and Shi, G.-Y.: Analysis of residual mean transport in the stratosphere 1. Model description and comparison with satellite data, J. Geophys. Res., 105, 19991–20011, 2000. Sjostedt, S J., Huey, L G., Tanner, D J., Peischl, J., Chen, G., Dibb, J E., Lefer, B., Hutterli, M A., Beyersdorf, A J., Blake, N J., Blake, D R., Sueper, D., Ryerson, T., Burkhart, J., and Stohl, A.: Observations of hydroxyl and the sum of peroxy radicals at Summit, Greenland during summer 2003, Atmos. Env., 41, 5122–5137, 2007. Stroud, C., Madronich, S., Atlas, E., Ridley, B., Flocke, F., Weinheimer, A., Talbot, B., Fried, A., Wert, B., Shetter, R., Lefer, B., Coffey, M., Heikes, B., and Blake, D.: Photochemistry in the arctic free troposphere: \chemNO_x budget and the role of odd nitrogen reservoir recycling, Atmos. Env., 37, 3351–3364, 2003. Terao, Y., Logan, J A., Douglass, A R., and Stolarski, R S.: Contribution of stratospheric ozone to the interannual variability of tropospheric ozone in the northern extratropics, J. Geophys. Res, 113, D18309, doi:10.1029/2008JD009854, 2008. Thompson, A M.: The oxidizing capacity of the earth's atmosphere: Probable past and future changes, Science, 256, 1157–1165, 1992. Thornton, J A., Braban, C F., and Abbatt, J P D.: \chemN_2O_5 hydrolysis on sub-micron organic aerosol: The effect of relative humidity, particle phase and particle size, Phys. Chem. Chem. Phys., 5, 4593–4603, 2003. Tie, X., Emmons, L., Horowitz, L., Brasseur, G., Ridley, B., Atlas, E., Stround, C., Hess, P., Klonecki, A., Madronich, S., Talbot, R., and Dibb, J.: Effect of sulfate aerosol on tropospheric NO_x and ozone budgets: Model simulations and TOPSE evidence, J. Geophys. Res, 108, 8364, doi:/10.1029/2001JD001508, 2003. van der Werf, G R., Randerson, J T., Giglio, L., Collatz, G H., and Kasibhatla, P S.: Interannual variability in global biomass burning emission from 1997 to 2004, Atmos. Chem. Phys., 6, 3423–3411, 2006. Wagenbach, D., Legrand, M., Fischer, H., Pichlmayer, F., and Wolff, E W.: Atmospheric near-surface nitrate at coastal Antarctic sites, J. Geophys. Res., 103, 11007–11020, 1998. Wagner, T. and Platt, U.: Satellite mapping of enhanced \chemBrO concentrations in the troposphere, Nature, 395, 486–490, 1998. Wang, Y H., Jacob, D J., and Logan, J A.: Global simulation of tropospheric \chemO_3-NO_x hydrocarbon chemistry 1. Model formulation, J. Geophys. Res., 103, 10713–710725, 1998. Wang, H., Jacob, D J., Sager, P L., Streets, D G., Park, R J., Gilliland, A B., and Donkelaar, A V.: Surface ozone background in the United States: Canadian and Mexican pollution influences, Atmos. Environ., in press, 2009. Wang, J S., McElroy, M B., Logan, J A., Palmer, P I., Chameides, W L., Wang, Y., and Megretskaia, I A.: A~quantitative assessment of uncertainties affecting estimates of global mean \chemOH derived from methyl chloroform observations, J. Geophys. Res, 113, D12302, doi:10.1029/2007JD008496, 2008. Weller, R., Jones, A E., Wille, A., Jacobi, H.-W., McIntyre, H P., Sturges, W T., Huke, M., and Wagenbach, D.: Seasonality of reactive nitrogen oxides (NO_y) at Neumayer Station, Antarctica, J. Geophys. Res, 107, 4673, doi:10.1029/2002JD002495, 2002. Wesely, M L.: Parameterization of surface resistances to gaseous dry deposition in regional-scale numerical-models, Atmos. Env., 23, 1293–1304, 1989. Wild, O., Zhu, Q., and Prather, M J.: Fast-J: Accurate simulation of in- and below-cloud photolysis in global chemical models, J. Atm. Chem., 37, 245–282, 2000. Wu, S., Mickley, L J., Jacob, D J., Logan, J A., Yantosca, R M., and Rind, D.: Why are there large differences between models in global budgets of tropospheric ozone?, J. Geophys. Res., 112, D05302, doi:10.1029/2006JD007801, 2007. Yienger, J J. and Levy, H.: Empirical model of global soil-biogenic NO_x emissions, J. Geophys. Res., 100, 11447–11464, 1995. Zahn, A., Franz, P., Bechtel, C., Groob, J.-U., and Röckmann, T.: Modelling the budget of middle atmospheric water vapour isotopes, Atmos. Chem. Phys., 6, 2073–2090, 2006. Zhang, L., Gong, S., Padro, J., and Barrie, L.: A~size-segregated particle dry deposition scheme for an atmosopheric aerosol module, Atmos. Env., 35, 549–560, 2001. 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 on Notrh America: an integrated analysis using satellite, aircraft, ozonesonde, and surface observations, Atmos. Chem. Phys., 8, 6117–6136, 2008. Zhang, Q. and Anastasio, C.: Conversion of fogwater and aerosol organic nitrogen to ammonium, nitrate, and NO_x during exposure to simulated sunlight and ozone, Environ. Sci. Technol., 37, 3522–3530, doi:10.1021/es034114x, 2003.