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Urban ozone over North America from soundings: Mixed influences from pollution, stratosphere, lightning and convection

Anne M. Thompson, Penn State Univ., University Park, PA; and A. M. Luzik, S. K. Miller, J. C. Witte, G. Morris, S. J. Oltmans, B. Rappenglueck, D. W. Tarasick, J. E. Yorks, and E. Joseph

During INTEX-A (summer 2004), a North American ozonesonde network was initiated to investigate variability in the vertical structure of tropospheric ozone: IONS-04 (INTEX [Intercontinental Transport Experiment] Ozonesonde Network Study). IONS-04 consisted of 11 stations across the US and eastern Canada [Thompson et al., 2007]. Nearly 300 midday launches were coordinated over a six-week period, 1 July-15 August 2004. Influences on free tropospheric O3 were computed for each sounding, assuming the following components: regional convection and lightning; stratospheric; and advected (i.e., a mixture of recently imported ozone and aged, background ozone). Determination of the budget was based on analysis of persistent layers in each ozone and P-T-U sounding, a method referred to as Laminar Identification (“LID” in Thompson et al., 2008; Yorks et al., 2008). Stratospheric ozone was found to be responsible for 25% of tropospheric ozone (free tropospheric ozone plus boundary layer ozone) for six northeastern North American stations in 2004. During the INTEX-B (Intercontinental Chemical Transport Experiment)/MILAGRO (Megacities Initiative: Local and Global Research Observations) experiments in March-May 2006 and the TEXAQS-II/GOMACCS (Texas Air Quality Study/Gulf of Mexico Atmospheric Chemistry and Climate Study) in August-September 2006, regular IONS-06 (), ozonesonde launches were made over 15 North American sites (spring) and 22 sites (summer), resulting in ~700 profiles. Satellite validation and model comparisons, as well as LID O3 budgets were supported by IONS-06. Over all stations, local and imported O3 intermingles with O3 from regional convection, lightning and stratosphere-troposphere exchange. The day-to-day variability of tropospheric O3 over the Mexico City Basin (MCB; 19N, 99W) and Houston (30N, 95W) was noteworthy. MCB and Houston profiles displayed a double tropopause in most soundings and a subtropical tropopause layer with frequent wave disturbances, identified through O3 laminae as gravity-wave induced. Tropospheric ozone with stratospheric origins were present on 39% (MCB) and 60% (Houston) of summer days. During the 2008 ARC-IONS (ARCTAS = Arctic Research on Composition of the Troposphere with Aircraft and Satellites), coordinated sondes operated from 1-20 April 2008 and 26 June-12 July 2008, for a total of > 400 soundings. During winter-spring, industrial sources contributed to “arctic haze” transport patterns. In summer, eastern North America was subject to typical urban pollution; northwestern and central North America was affected by Asian pollution and emissions from forest fires in the western US and central Canada.

  Recorded presentation

Session 1, Field, laboratory, and modeling studies of air quality—I
Monday, 12 January 2009, 10:45 AM-12:00 PM, Room 127A

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