Avery, Melody and Twohy, Cynthia and McCabe, David and Joiner, Joanna and Severance, Kurt and Atlas, Eliot and Blake, Donald and Bui, T. P. and Crounse, John and Dibb, Jack and Diskin, Glenn and Lawson, Paul and McGill, Matthew and Rogers, David and Sachse, Glen and Scheuer, Eric and Thompson, Anne M. and Trepte, Charles and Wennberg, Paul and Ziemke, Jerald (2010) Convective distribution of tropospheric ozone and tracers in the Central American ITCZ region: Evidence from observations during TC4. Journal of Geophysical Research D, 115 . Art. No. D00J21 . ISSN 0148-0227 http://resolver.caltech.edu/CaltechAUTHORS:20101109-075906062
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During the Tropical Composition, Clouds and Climate Coupling (TC4) experiment that occurred in July and August of 2007, extensive sampling of active convection in the ITCZ region near Central America was performed from multiple aircraft and satellite sensors. As part of a sampling strategy designed to study cloud processes, the NASA ER-2, WB-57 and DC-8 flew in stacked “racetrack patterns” in convective cells. On July 24, 2007, the ER-2 and DC-8 probed an actively developing storm and the DC-8 was hit by lightning. Case studies of this flight, and of convective outflow on August 5, 2007 reveal a significant anti-correlation between ozone and condensed cloud water content. With little variability in the boundary layer and a vertical gradient, low ozone in the upper troposphere indicates convective transport. Because of the large spatial and temporal variability in surface CO and other pollutants in this region, low ozone is a better convective indicator. Lower tropospheric tracers methyl hydrogen peroxide, total organic bromine and calcium substantiate the ozone results. OMI measurements of mean upper tropospheric ozone near convection show lower ozone in convective outflow. A mass balance estimation of the amount of convective turnover below the tropical tropopause transition layer (TTL) is 50%, with an altitude of maximum convective outflow located between 10 and 11 km, 4 km below the cirrus anvil tops. It appears that convective lofting in this region of the ITCZ is either a two-stage or a rapid mixing process, because undiluted boundary layer air is never sampled in the convective outflow.
|Additional Information:||© 2010 American Geophysical Union. Received 28 October 2009; revised 17 May 2010; accepted 7 June 2010; published 13 October 2010. The authors thank the NASA Middle Atmosphere and Tropospheric Chemistry Programs for funding, and Program Managers Michael Kurylo and Hal Maring for launching sondes from the DC‐8. We thank Lenny Pfister for all sorts of meteorological information and consultation. We thank Gary Morris for providing the Las Tablas sonde data, and we thank Alex Bryan and David Lutz for launching all of these Panama sondes. Holger Voemel provided the Alajuela ozonesonde data, and Ru‐shan Gao provided ozone measurements from the WB‐57. Ross Salawitch and Tim Canty provided the plot of total organic bromine, and we are grateful for many helpful discussions. We also thank Mario Rana for DC‐8 fast‐response tracer lag correlations and Ali Aknan for “Chemical Digital Atlas” plots and calculations of statistical vertical tracer distributions during various tropospheric aircraft field missions (http://www‐air.larc.nasa.gov/cgi‐bin/datlas). We are grateful to K.A. Masserie and E. Dlugokencky at NOAA CMDL for the Barbados and Bahia methane measurements, and to Pat Minnis and his group for the GOES satellite images and loops.|
|Subject Keywords:||convection; vertical transport; chemical tracers|
|Official Citation:||Avery, M., et al. (2010), Convective distribution of tropospheric ozone and tracers in the Central American ITCZ region: Evidence from observations during TC4, J. Geophys. Res., 115, D00J21, doi:10.1029/2009JD013450.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||19 Nov 2010 23:34|
|Last Modified:||26 Dec 2012 12:36|
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