<?xml version="1.0" encoding="utf-8" standalone="no"?>
<!DOCTYPE article SYSTEM "http://www.atmos-chem-phys.net/inc/acp/copernicus.dtd">
<article language="en">
	<journal>
		<journal_title>Atmospheric Chemistry and Physics</journal_title>
		<journal_url>www.atmos-chem-phys.net</journal_url>
		<issn>1680-7316</issn>
		<eissn>1680-7324</eissn>
		<volume_number>10</volume_number>
		<issue_number>1</issue_number>
		<publication_year>2010</publication_year>
	</journal>
	<doi>10.5194/acp-10-107-2010</doi>
	<article_url>http://www.atmos-chem-phys.net/10/107/2010/</article_url>
	<abstract_html>http://www.atmos-chem-phys.net/10/107/2010/acp-10-107-2010.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys.net/10/107/2010/acp-10-107-2010.pdf</fulltext_pdf>
	<start_page>107</start_page>
	<end_page>119</end_page>
	<publication_date>2010-01-08</publication_date>
	<article_title content_type="html">Lightning NO&lt;sub&gt;x&lt;/sub&gt; emissions over the USA constrained by TES ozone observations and the GEOS-Chem model</article_title>
	<authors>
		<author numeration="1" affiliations="1,5">
			<name>L. Jourdain</name>
			<email>line.jourdain@cnrs-orleans.fr</email>
		</author>
		<author numeration="2" affiliations="1">
			<name>S. S. Kulawik</name>
		</author>
		<author numeration="3" affiliations="2">
			<name>H. M. Worden</name>
		</author>
		<author numeration="4" affiliations="3">
			<name>K. E. Pickering</name>
		</author>
		<author numeration="5" affiliations="1">
			<name>J. Worden</name>
		</author>
		<author numeration="6" affiliations="4">
			<name>A. M. Thompson</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA</affiliation>
		<affiliation numeration="2" content_type="html">National Center for Atmospheric Research, P.O. Box 3000 Boulder, CO 80307, USA</affiliation>
		<affiliation numeration="3" content_type="html">NASA Goddard Space Flight Center, Greenbelt, MD 20771 USA</affiliation>
		<affiliation numeration="4" content_type="html">Department of Meteorology, Pennsylvania State University, University Park, PA 16802,USA</affiliation>
		<affiliation numeration="5" content_type="html">now at: Laboratoire de Physique et Chimie de l&apos;Environnement et de l&apos;Espace et Université d&apos;Orléans, Orléans, France</affiliation>
	</affiliations>
	<abstract content_type="html">Improved estimates of NO&lt;sub&gt;x&lt;/sub&gt; from lightning sources are required to
understand tropospheric NO&lt;sub&gt;x&lt;/sub&gt; and ozone distributions, the oxidising
capacity of the troposphere and corresponding feedbacks between chemistry
and climate change. In this paper, we report new satellite ozone
observations from the Tropospheric Emission Spectrometer (TES) instrument
that can be used to test and constrain the parameterization of the lightning
source of NO&lt;sub&gt;x&lt;/sub&gt; in global models. Using the National Lightning Detection
(NLDN) and the Long Range Lightning Detection Network (LRLDN) data as well
as the HYPSLIT transport and dispersion model, we show that TES provides
direct observations of ozone enhanced layers downwind of convective events
over the USA in July 2006. We find that the GEOS-Chem global
chemistry-transport model with a parameterization based on cloud top height,
scaled regionally and monthly to OTD/LIS (Optical Transient Detector/Lightning
Imaging Sensor) climatology, captures the ozone enhancements seen
by TES. We show that the model&apos;s ability to reproduce the location of the
enhancements is due to the fact that this model reproduces the pattern of
the convective events occurrence on a daily basis during the summer of 2006
over the USA, even though it does not well represent the relative
distribution of lightning intensities. However, this model with a value of 6 Tg N/yr
for the lightning source (i.e.: with a mean production of 260 moles
NO/Flash over the USA in summer) underestimates the intensities of the ozone
enhancements seen by TES. By imposing a production of 520 moles NO/Flash for
lightning occurring in midlatitudes, which better agrees with the values
proposed by the most recent studies, we decrease the bias between TES and
GEOS-Chem ozone over the USA in July 2006 by 40%. However, our conclusion
on the strength of the lightning source of NO&lt;sub&gt;x&lt;/sub&gt; is limited by the fact
that the contribution from the stratosphere is underestimated in the
GEOS-Chem simulations.</abstract>
	<references>
		<reference numeration="1" content_type="text"> Beer, R., Glavich, T. A., and Rider, D. M.: Tropospheric emission spectrometer for the Earth Observing System&apos;s Aura satellite, Appl. Optics, 40, 2356–2367, 2001. </reference>
		<reference numeration="2" content_type="text"> Beer, R.: TES on the Aura mission: Scientific objectives, measurements, and analysis overview, IEEE T. Geosci. Remote, 44, 1102–1105, 2006. </reference>
		<reference numeration="3" content_type="text"> Boccippio, D. J., Cummins, K. L., Christian, H. J., et al.: Combined satellite- and surface-based estimation of the intracloud-cloud-to-ground lightning ratio over the continental United States, Mon. Weather Rev., 129, 108–122, 2001. </reference>
		<reference numeration="4" content_type="text"> Boccippio, D. J.: Lightning Scaling Relations Revisited, Atmos. Environ., 59, 1086–1104, 2002. </reference>
		<reference numeration="5" content_type="text"> Bowman, K. W., Rodgers, C. D., Kulawik, S. S., Worden, J., Sarkissian, E., Osterman, G., Steck, T., Lou, M., Eldering, A., Shephard, M., Worden, H., Lampel, M., Clough, S., Brown, P., Rinsland, C., Gunson, M., and Beer, R.: Tropospheric Emission Spectrometer: Retrieval Method and Error Analysis, IEEE T. Geosci. Remote, 44, 1297–1307, 2006. </reference>
		<reference numeration="6" content_type="text"> Brunner, D., Staehelin, J., and Jeker, D.: Large-Scale Nitrogen Oxide Plumes in the Tropopause Region and Implications for Ozone, Science, 182, 1305–1309, 1998. </reference>
		<reference numeration="7" content_type="text"> Brunner, D., Staehelin, J., Jeker, D., Wernli, H., and Schumman, U.: Nitrogen oxides and ozone in the tropopause region of the Northern Hemisphere : Measurements from commercial aircraft in 1995/1996 and 1997, J. Geophys. Res., 106, 27673–27699, 2001. </reference>
		<reference numeration="8" content_type="text"> Christian, H. J., Blakeslee, R. J., Boccippio, D. J., Boeck, W. L., Buechler, D. E., Driscoll, K. T., Goodman, S. J., Hall, J. M., Koshak, W. J., Mach, D. M., and Stewart, M. F.: Global frequency and distribution of lightning as observed from space by the Optical Transient Detector, J. Geophys. Res., 108, 4005, doi:10.1029/2002JD002347, 2003. </reference>
		<reference numeration="9" content_type="text"> Cooper, O. R., Stohl, A., Trainer, M., Thompson, A. M., Witte, J. C., Oltmans, S. J., Morris, G., Pickering, K. E., Crawford, J. H., Chen, G., Cohen, R. C., Bertram, T. H., Wooldridge, P., Perring, A., Brune, W. H., Merrill, J., Moody, J. L., Tarasick, D., Nédélec, P., Forbes, G., Newchurch, M. J., Schmidlin, F. J., Johnson, B. J., Turquety, S., Baughcum, S. L., Ren, X., Fehsenfeld, F. C., Meagher, J. F., Spichtinger, N., Brown, C. C., McKeen, S. A., McDermid, I. S., and Leblanc, T.: Large upper tropospheric ozone enhancements above mid-latitude North America during summer: In situ evidence from the IONS and MOZAIC ozone measurement network, J. Geophys. Res., 111, D24S05, doi:10.1029/2006JD007306, 2006. </reference>
		<reference numeration="10" content_type="text"> Cooper, O. R., Trainer, M., Thompson, A. M., Oltmans, S. J., Tarasick, D. W., Witte, J. C., Stohl, A., Eckhardt, S., Lelieveld, J., Newchurch, M. J., Johnson, B. J., Portmann, R. W., Kalnajs, L., Dubey, M. K., Leblanc, T., McDermid, I. S., Forbes, G., Wolfe, D., Carey-Smith, T., Morris, G. A., Lefer, B., Rappenglück, B., Joseph, E., Schmidlin, F., Ravishankara, A., Meagher, J., Fehsenfeld, F. C., Keating, T. J., Van Curen, R. A., and Minschwaner, K.: Evidence for a recurring eastern North American upper tropospheric ozone maximum during summer, J. Geophys. Res., 112, D23306, doi:10.1029/2007JD008910, 2007. </reference>
		<reference numeration="11" content_type="text"> Crawford, J., Davis, D., Olson, J., Chen, G., Liu, S., Fuelberg, H., Hannan, J., Kondo, Y., Anderson, B., Gregory, G., Sachse, G., Talbot, R., Viggiano, A., Heikes, B., Snow, J., Singh, H., and Blake, D.: Evolution and chemical consequences of lightning-produced NO&lt;sub&gt;x&lt;/sub&gt; observed in the North Atlantic upper troposphere, J. Geophys. Res., 105, 19795–19809, 2000. </reference>
		<reference numeration="12" content_type="text"> DeCaria, A. J., Pickering, K. E., Stenchikov, G. L., Scala, J. R., Stith, J. L., Dye, J. E., Ridley, B. A., and Laroche, P.: A cloud-scale model study of lightning-generated NO&lt;sub&gt;x&lt;/sub&gt; in an individual thunderstorm during STERAO-A, J. Geophys. Res., 105, 11601–11616, 2000. </reference>
		<reference numeration="13" content_type="text"> DeCaria, A. J., Pickering, K. E., Stenchikov, G. L., and Ott, L. E.: Lightning-generated NO&lt;sub&gt;x&lt;/sub&gt; and its impact on tropospheric ozone production: A three-dimensional modeling study of a Stratosphere-Troposphere Experiment: Radiation, Aerosols and Ozone (STERAO-A) thunderstorm, J. Geophys. Res., 110, D14303, doi:10.1029/2004JD005556, 2005. </reference>
		<reference numeration="14" content_type="text"> Draxler, R. R. and Rolph, G. D.: HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model. Web address: http://www.arl.noaa.gov/ready/hysplit4.html, NOAA Air Resources Laboratory, Silver Spring, MD, 2003. </reference>
		<reference numeration="15" content_type="text"> Folkins, I., Bernath, P., Boone, C., Donner, L. J., Eldering, A., Lesins, G., Martin, R. V., Sinnhuber, B.-M., and Walker, K.: Testing convective parameterizations with tropical measurements of HNO&lt;sub&gt;3&lt;/sub&gt;, CO, H&lt;sub&gt;2&lt;/sub&gt;O, and O&lt;sub&gt;3&lt;/sub&gt;: Implications for the water vapor budget, J. Geophys. Res., 111, D23304, doi:10.1029/2006JD007325, 2006. </reference>
		<reference numeration="16" content_type="text"> Grogan, M. J.: Report on the 2002–2003 US NLDN system-wide upgrade, Vaisala Thunderstorm, Tuscon, Ariz., 2004. </reference>
		<reference numeration="17" content_type="text"> Horowitz, L., Walters, S., Mauzerall, D., Emmons, L., Rasch, P., Granier, C., Tie, X., Lamarque, J.-F., Schultz, M., Tyndall, G., Orlando, J., and Brasseur, G.: A global simulation of tropospheric ozone and related tracers: Description and evaluation of MOZART, version 2, J. Geophys. Res., 108, 4784, doi:10.1029/2002JD002853, 2003. </reference>
		<reference numeration="18" content_type="text"> Hudman, R. C., Jacob, D. J., Turquety, S., Leibensperger, E. M., Murray, L. T., Wu, S., Gilliland, A. B., Avery, M., Bertram, T. H., Brune, W., Cohen, R. C., Dibb, J. E., Flocke, F. M., Fried, A., Holloway, J., Neuman, J. A., Orville, R., Perring, A., Ren, X., Sachse, G. W., Singh, H. B., Swanson, A., and Wooldridge, P. J.: Surface and lightning sources of nitrogen oxides over the United States: Magnitudes, chemical evolution, and outflow, J. Geophys. Res., 112, D12S05, doi:10.1029/2006JD007912, 2007. </reference>
		<reference numeration="19" content_type="text"> Huntrieser, H., Schumann, U., Schlager, H., Höller, H., Giez, A., Betz, H.-D., Brunner, D., Forster, C., Pinto Jr., O., and Calheiros, R.: Lightning activity in Brazilian thunderstorms during TROCCINOX: implications for NO&lt;sub&gt;x&lt;/sub&gt; production, Atmos. Chem. Phys., 8, 921–953, 2008. </reference>
		<reference numeration="20" content_type="text"> Jaeglé, L., Jacob, D. J., Wang, Y., Weinheimer, A. J., Ridley, B. A., Campos, T. L., Sasche, G. W., and Hagen, D. E.: Sources and chemistry of NO&lt;sub&gt;x&lt;/sub&gt; in the upper troposphere over the United Stated, Geosphys. Res. Lett., 25, 1705–1708, 1998. </reference>
		<reference numeration="21" content_type="text"> Jaeglé, L., Steinberger, L., Martin, R. V., and Chance, K.: Global partitioning of NO&lt;sub&gt;x&lt;/sub&gt; sources using satellite observations: Relative roles of fossil fuel combustion, biomass burning and soil emissions, Faraday Discuss., 130, 407–423, 2005. </reference>
		<reference numeration="22" content_type="text"> Jeker, D. P., Pfister, L., Thompson, A. M., Brunner, D., Boccipio, D. J., Pickering, K. E., Wernli, H., Kondoa, Y., and Staehelin, J.: Measurements of nitrogen oxides at the tropopause: Attribution to convection and correlation with lightning, J. Geophys. Res., 105, 3679–3700, 2000. </reference>
		<reference numeration="23" content_type="text"> Jourdain, L., Worden, H. M., Worden, J. R., Bowman, K., Li, Q., Eldering, A., Kulawik, S. S., Osterman, G., Boersma, K. F., Fisher, B., Rinsland, C. P., Beer, R., and Gunson, M.: Tropospheric vertical distribution of tropical Atlantic ozone observed by TES during the northern African biomass burning season, Geophys. Res. Lett., 34, L04810, doi:10.1029/2006GL028284, 2007. </reference>
		<reference numeration="24" content_type="text"> Li, D. and Shine, K. P.: A 4-Dimensionnal Ozone Climatology for UGAMP Models, UGAMP Internal Report N 35, 1995. </reference>
		<reference numeration="25" content_type="text"> Li, Q., Jacob, D. J., Park, R., Wang, Y., Heald, C. L., Hudman, R., Yantosca, R. M., Martin, R. V., and Evans, M.: North American pollution outflow and the trapping of convectively lifted pollution by upper-level anticyclone, J. Geophys. Res., 110, D10301, doi:10.1029/2004JD005039, 2005. </reference>
		<reference numeration="26" content_type="text"> Liu, S. C., Yu, H., Wang, Y., Davis, D. D., Kondo, Y., Anderson, B. E., Sachse, G. W., Gregory, G. L., Ridley, B., Fuelburg, H. E., Thompson, A. M., and Singh, H. B.: Sources of reactive nitrogen in the upper troposphere during SONEX, Geophys. Res. Lett., 26, 2441–2444, 1999. </reference>
		<reference numeration="27" content_type="text"> Martin, R. V., Sioris, C. E., Chance, K., Ryerson, T. B., Bertram, T. H., Wooldridge, P. J., Cohen, R. C., Neuman, J. A., Swanson, A., and Flocke, F. M.: Evaluation of space-based constraints on global nitrogen oxide emissions with regional aircraft measurements over and downwind of eastern North America, J. Geophys. Res., 111, D15308, doi:10.1029/2005JD006680, 2006. </reference>
		<reference numeration="28" content_type="text"> McLinden, C. A., Olsen, S. C., Hannegan, B., Wild, O., Prather, M. J., and Sundet, J.: Stratospheric ozone in 3-D models: A simple chemistry and the cross-tropopause flux, J. Geophys. Res., 105, 14653–14666, 2000. </reference>
		<reference numeration="29" content_type="text"> Nassar, R., Logan, J. A., Worden, H. M., Megretskaia, I. A., Bowman, K. W., Osterman, G. B., Thompson, A. M., Tarasick, D., Austin, S., Claude, H., Dubey, M., Hocking, W., Johnson, B., Joseph, E., Merrill, J. T., Morris, G., Newchurch, M. J., Oltmans, S., Posny, F., Schmidlin, F., Vömel, H., Whiteman, D., and Witte, J.: Validation of Tropospheric Emission Spectrometer (TES) Nadir Ozone Profiles Using Ozonesonde Measurements, J. Geophys. Res., 113, D15S17, doi:10.1029/2007JD008819, 2008. </reference>
		<reference numeration="30" content_type="text"> Osterman, G. B., Kulawik, S. S., Worden, H. M., Richards, N. A. D., Fisher, B. M., Eldering, A., Shephard, M. W., Froidevaux, L., Labow, G., Luo, M., Herman, R. L., Bowman, K. W., and Thompson, A. M.: Validation of Tropospheric Emission Spectrometer (TES) Measurements of the Total, Stratospheric and Tropospheric Column Abundance of Ozone, J. Geophys. Res., 113, D15S16, doi:10.1029/2007JD008801, 2008. </reference>
		<reference numeration="31" content_type="text"> Ott, L. E., Pickering, K. E., Stenchikov, G. L., DeCaria, A. J., Lin, R.-F., Wang, D., Lang, S., and Tao, W.-K.: Production of lightning NO&lt;sub&gt;x&lt;/sub&gt; and its vertical distribution calculated from 3-D cloud-scale transport model simulations, J. Geophys. Res., in press, 2009. </reference>
		<reference numeration="32" content_type="text"> Park, M., Randel, W. J., Kinnison, D. E., Garcia, R. R., and Choi, W.: Seasonal variation of methane, water vapor, and nitrogen oxides near the tropopause: Satellite observations and model simulations, J. Geophys. Res., 109, D03302, doi:10.1029/2003JD003706, 2004. </reference>
		<reference numeration="33" content_type="text"> Parrington, M., Jones, D. B. A., Bowman, K. W., Horowitz, L. W., Thompson, A. M., Tarasick, D., and Witte, J. C.: Constraining the Summertime Tropospheric Ozone Distribution over North America through Assimilation of Observations from the Tropospheric Emission Spectrometer, J. Geophys. Res., 113, D18307, doi:10.1029/2007JD009341, 2008. </reference>
		<reference numeration="34" content_type="text"> Pickering, K. E., Wang, Y., Tao, W.-K., Price, C., and Müller, J.-F.: Vertical distributions of lightning NO&lt;sub&gt;x&lt;/sub&gt; for use in regional and global chemical transport models, J. Geophys. Res., 103, 31203–31216, doi:10.1029/98JD02651, 1998. </reference>
		<reference numeration="35" content_type="text"> Price, C. and Rind, D.: A simple lightning parameterization for calculating global lightning distributions, J. Geophys. Res., 97, 9919–9933, 1992. </reference>
		<reference numeration="36" content_type="text"> Richards, N. A. D., Osterman, G. B., Browell, E. V., Hair, J. W., Avery, M., and Li, Q.: Validation of Tropospheric Emission Spectrometer ozone profiles with aircraft observations during the Intercontinental Chemical Transport Experiment-B, J. Geophys. Res., 113, D16S29, doi:10.1029/2007JD008815, 2008. </reference>
		<reference numeration="37" content_type="text"> Ridley, B. A., Walega, J. G., Dye, J. E., and Grahek, F. E.: Distributions of NO, NO&lt;sub&gt;x&lt;/sub&gt;, NO&lt;sub&gt;y&lt;/sub&gt;, and O&lt;sub&gt;3&lt;/sub&gt; to 12 km altitude during the summer monsoon season over New Mexico, J. Geophys. Res., 99(D12), 25519–25534, doi:10.1029/94JD02210, 1994. </reference>
		<reference numeration="38" content_type="text"> Rodgers, C. D.: Inverse Methods for Atmospheric Sounding: Theory and Practise, Singapore: World Scientific, Series on Atmospheric, Oceanic and planetary physics, 2, 1–11, 2000. </reference>
		<reference numeration="39" content_type="text"> Sauvage, B., Martin, R. V., van Donkelaar, A., Liu, X., Chance, K., Jaeglé, L., Palmer, P. I., Wu, S., and Fu, T.-M.: Remote sensed and in situ constraints on processes affecting tropical tropospheric ozone, Atmos. Chem. Phys., 7, 815–838, 2007. </reference>
		<reference numeration="40" content_type="text"> Schumann, U. and Huntrieser, H.: The global lightning-induced nitrogen oxides source, Atmos. Chem. Phys., 7, 3823–3907, 2007. </reference>
		<reference numeration="41" content_type="text"> Stith, J., Dye, J., Ridley, B., Laroche, P., Defer, E., Baumann, K., Hübler, G., Zerr, R., and Venticinque, M.: NO signatures from lightning flashes, J. Geophys. Res., 104, 16081–16089, 1999. </reference>
		<reference numeration="42" content_type="text"> Thompson, A. M., Pickering, K. E., Dickerson, R. R., Ellis, W. G., Jacob, D. J., Scala, J. R., Tao, W. K., McNamara, D. P., and Simpson, J.: Convective Transport over the central United States and its role in regional CO and ozone budgets, J. Geophys. Res., 99, 18703–18711, 1994. </reference>
		<reference numeration="43" content_type="text"> Thompson, A. M., Sparling, L. C., Kondo, Y., Anderson, B. E., Gregory, G. L., and Sachse, G. W.: Perspectives on NO, NOy and fine aerosol sources and variability during SONEX, Geophys. Res. Lett., 26, 3073–3076, 1999. </reference>
		<reference numeration="44" content_type="text"> Thompson, A. M., Stone, J. B., Witte, J. C., et al.: Intercontinental Chemical Transport Experiment Ozonesonde Network Study (IONS) 2004: 1 Summertime upper troposphere/lower stratosphere ozone over northeastern North America, J. Geophys. Res., 112, D12S12, doi:10.1029/2006JD007441, 2007a. </reference>
		<reference numeration="45" content_type="text"> Thompson, A. M., Stone, J. B., Witte, J. C., et al.: Intercontinental Chemical Transport Experiment Ozonesonde Network Study (IONS) 2004: 2. Tropospheric ozone budgets and variability over northeastern North America, J. Geophys. Res., 112, D12S13, doi:10.1029/2006JD007670, 2007b. </reference>
		<reference numeration="46" content_type="text"> Thompson, A. M., Yorks, J. E., Miller, S. K., Witte, J. C., Dougherty, K. M., Morris, G. A., Baumgardner, D., Ladino, L., and Rappenglück, B.: Tropospheric ozone sources and wave activity over Mexico City and Houston during MILAGRO/Intercontinental Transport Experiment (INTEX-B) Ozonesonde Network Study, 2006 (IONS-06), Atmos. Chem. Phys., 8, 5113–5125, 2008. </reference>
		<reference numeration="47" content_type="text"> Wang, Y., Logan, J. A., and Jacob, D. J.: Global simulation of tropospheric O3-NO&lt;sub&gt;x&lt;/sub&gt;-hydrocarbon chemistry 2. Model evaluation and global ozone budget, J. Geophys. Res. 103, 10727–10755, 1998. </reference>
		<reference numeration="48" content_type="text"> Worden, J., Kulawik, S. S., Shephard, M. W., Clough, S. A., Worden, H., Bowman, K., and Goldman, A.: Predicted errors of tropospheric emission spectrometer nadir retrievals from spectral window selection, J. Geophys. Res., 109, D09308, doi:10.1029/2004JD004522, 2004. </reference>
		<reference numeration="49" content_type="text"> Worden, H. M., Logan, J. A., Worden, J. R., Beer, R., Bowman, K., Clough, S. A., Eldering, A., Fisher, B. M., Gunson, M. R., Herman, R. L., Kulawik, S. S., Lampel, M. C., Luo, M., Megretskaia, I. A., Osterman, G. B., and Shephard, M. W.: Comparisons of Tropospheric Emission Spectrometer (TES) ozone profiles to ozonesondes: Methods and initial results, J. Geophys. Res., 112, D03309, doi:10.1029/2006JD007258, 2007. </reference>
		<reference numeration="50" content_type="text"> Yorks, J. E., Thompson, A. M., Joseph, E., and Miller, S. K.: The variability of free tropospheric ozone budgets over Beltsville, Maryland (39 N, 77 W) in the summers 2004–2007, Atmos. Environ., 43, 1827–1838, 2009. </reference>
	</references>
</article>

