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Auxiliary Material – Description of the GEOS-Chem model
The GEOS-Chem global 3-D chemical transport model [Bey et al., 2001] is used in this
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study. Version 9-01-03 (http://geos-chem.org) is used here at a horizontal resolution of 4°x5°.
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The model is described on 47 vertical levels, extending from the surface to 0.1 hPa including
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approximately 35 levels in the troposphere.
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GEOS-Chem contains a detailed simulation of HOx-NOx-VOC-O3-aerosol chemistry.
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The current chemical mechanism in GEOS-Chem includes the most recent JPL/IUPAC
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recommendations as implemented into GEOS-Chem by Mao et al. [2010]. The stratospheric
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ozone simulation uses the Linoz algorithm of McLinden et al. [2000]. The global lightning NOx
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source is 6 Tg N a-1 [Martin et al., 2007] and scaled to match OTD/LIS observations of
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lightning flashes as implemented in v9-01-03 by Murray et al. [2012].
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The model is driven by assimilated meteorological data provided by the Global Modeling
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and Assimilation Office (GMAO) at NASA Goddard Space Flight Center. GEOS-5
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meteorological fields for the years 2004-2010 are used here. GEOS-5 employs the relaxed
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Arakawa-Schubert convective parameterization for shallow and deep moist convection [Moorthi
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and Suarez, 1992]. Comparisons of mass divergence profiles indicate that the level of maximum
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convective outflow in GEOS-5 agrees well with observations [Mitovski et al., 2011].
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GEOS-Chem has been used in several recent studies of tropospheric ozone [Parrington et
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al., 2012; Cooper et al., 2011; Nassar et al., 2009]. The O3 simulation has been extensively
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evaluated against in situ measurements [Nassar et al., 2009; Sauvage et al., 2007; Zhang et al.,
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2010]. The GEOS-Chem fields generally reproduce changes in the tropospheric ozone column
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associated with El Niño [Chandra et al., 2002, 2003]
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References:
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Bey, I., D. J. Jacob, R. M. Yantosca, J. A. Logan, B. Field, A. M. Fiore, Q. Li, H. Liu, L. J.
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Mickley, and M. Schultz (2001), Global modeling of tropospheric chemistry with assimilated
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meteorology: Model description and evaluation, J. Geophys. Res., 106, 23,073-23,096.
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Chandra, S., J. R. Ziemke, P. K. Bhartia, and R. V. Martin (2002), Tropical tropospheric ozone:
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Implications for dynamics and biomass burning, J. Geophys., Res., 107,
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doi:10.129/2001JD000447
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Chandra et al. (2003), Tropospheric ozone at tropical and middle latitudes derived from
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TOMS/MLS residual: Comparison with a global model, J. Geophys. Res., 108, doi:
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10.1029/2002JD002912
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Mao, J. et al. (2010), Chemistry of hydrogen oxide radicals (HOx) in the Arctic troposphere in
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spring, Atm. Chem. Phys. 10(13), 5823-5838, doi: 10.5194/acp-10-5823-2010.
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Martin, R.V., B. Sauvage, I. Folkins, C.E. Sioris, C. Boone, P. Bernath, and J.R. Ziemke, Space-
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based constraints on the production of nitric oxide by lightning, J. Geophys. Res., 112, D09309,
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doi:10.1029/2006JD007831, 2007.
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McLinden, C.A, S. C. Olsen, B. Hannegan, O. Wild, M. J. Prather, J. Sundet (2000),
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Stratospheric ozone in 3-D models: a simple chemistry and the cross-tropopause flux, J.
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Geophys. Res., 105, 14653-14665, 2000.
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Mitovski, T., I. Folkins, R. V. Martin, and M. Cooper (2011), Testing convective transport on
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short timescales: comparisons with mass divergence and ozone anomaly patterns about high rain
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events, J. Geophys. Res., 117, D02109, doi:10.1029/2011JD016321, 2012.
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Moorthi, S. and M. J. Suarez (1992), Relaxed Arakawa-Schubert, A Parameterization of Moist
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Convection for General-Circulation Models. Mon. Wea. Rev. 120, 978-1002.
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Murray, L. T., D. J. Jacob, J. A. Logan, R. C. Hudman, and W. J. Koshak (2012), Optimized
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regional and interannual variability of lightning in a global chemical transport model constrained
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by LIS/OTD satellite data, J. Geophys. Res., 117, D20307, doi:10.1029/2012JD017934.
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Nassar, R., J. A. Logan, I. A. Megretskaia, L. T. Murray, L. Zhang, and D. B. A. Jones (2009),
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Analysis of tropical tropospheric ozone, carbon monoxide, and water vapor during the 2006 El
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Niño using TES observations and the GEOS‐Chem model, J. Geophys. Res., 114, D17304,
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doi:10.1029/2009JD011760.
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Parrington, M et al (2012), The influence of boreal biomass burning emissions on the distribution
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of tropospheric ozone over North America and the North Atlantic during 2010, Atm. Chem. Phys.
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12, 2077-2098, doi:10.5194/acp-12-2077-2012.
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Sauvage, B., R. V. Martin, A. van Donkelaar, X. Liu, K. Chance, L. Jaeglé, P. I. Palmer, S. Wu,
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and T.‐M. Fu (2007b), Remote sensed and in situ constraints on processes affecting tropical
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tropospheric ozone, Atmos. Chem. Phys., 7, 815–838, doi:10.5194/acp-7-815-2007.
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Zhang, L., D. J. Jacob, X. Liu, J. A. Logan, K. Chance, A. Eldering, and B. R. Bojkov (2010),
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Intercomparison methods for satellite measurements of atmospheric composition: Application to
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tropospheric ozone from TES and OMI, Atmos. Chem. Phys. Discuss., 10, 1417–1456,
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doi:10.5194/acpd-10-1417-2010.
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