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. Thompson (1) , J. E. Yorks (1) , S. K. Miller (1) , J. C. Witte (2) , K. M. Dougherty (1) , G. A. Morris (3) , D. Baumgardner (4) , L. Ladino (4) , B. Rappenglueck (5)

1 PennState Meteorology Department
2 SSAI - Science Systems and Applications, Inc. [Lanham]
3 Valparaiso University
4 Center for Chemistry of the Atmosphere
5 Geosciences Department

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; http://croc.gsfc.nasa.gov/intexb/ions06.html), regular 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.

Domaines: Océan, Atmosphère

A. M. Thompson, J. E. Yorks, S. K. Miller, J. C. Witte, K. M. Dougherty, et al.. Tropospheric ozone sources and wave activity over Mexico City and Houston during MILAGRO/Intercontinental Transport Experiment (INTEX-B) Ozonesonde Network Study, 2006 (IONS-06). Atmospheric Chemistry and Physics Discussions, 2008, 8 (2), pp.5979-6007. ⟨hal-00304054⟩