Tropospheric ozone sources and wave activity over Mexico City and Houston during MILAGRO/Intercontinental Transport Experiment (INTEX-B) Ozonesonde Network Study, 2006 (IONS-06) A. M. Thompson1, J. E. Yorks1, S. K. Miller1, J. C. Witte2,*, K. M. Dougherty1, G. A. Morris3, D. Baumgardner4, L. Ladino4, and B. Rappenglück5 1The Pennsylvania State University, Department of Meteorology, 503 Walker Building, University Park, PA, USA 2SSAI of Lanham, MD, USA 3Valparaiso University, Dept. of Physics and Astronomy, Valparaiso, IN, USA 4UNAM (Autonomous University of Mexico), CCA – Center for Chemistry of the Atmosphere, Mexico City, Mexico 5University of Houston, Geosciences Department, Old Sciences Bldg, Houston, TX, USA *also at: NASA/Goddard Space Flight Center, Greenbelt, MD, USA
Abstract. During the INTEX-B (Intercontinental Chemical Transport Experiment)/ MILAGRO
(Megacities Initiative: Local and Global Research Observations) experiments
in March 2006 and the associated IONS-06 (INTEX Ozonesonde Network Study;
ozonesonde launches were made over 15 North American sites. The soundings
were strategically positioned to study inter-regional flows and
meteorological interactions with a mixture of tropospheric O3 sources:
local pollution; O3 associated with convection and lightning;
stratosphere-troposphere exchange. The variability of tropospheric O3
over the Mexico City Basin (MCB; 19° N, 99° W) and Houston (30° N, 95° W) is
reported here. 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.
Ozonesondes launched over both cities in August and September 2006 (IONS-06,
Phase 3) displayed a thicker tropospheric column O3 (~7 DU or
15–20%) than in March 2006; nearly all of the increase was in the free
troposphere. In spring and summer, O3 laminar structure manifested
mixed influences from the stratosphere, convective redistribution of O3
and precursors, and O3 from lightning NO. Stratospheric O3 origins
were present in 39% (MCB) and 60% (Houston) of the summer sondes.
Comparison of summer 2006 O3 structure with summer 2004 sondes
(IONS-04) over Houston showed 7% less tropospheric O3 in 2006. This
may reflect a sampling contrast, August to mid-September 2006 instead of
July-mid August 2004.
Citation: 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, doi:10.5194/acp-8-5113-2008, 2008.