Atmos. Chem. Phys. Discuss., 7, 13035-13076, 2007
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Basin-scale wind transport during the MILAGRO field campaign and comparison to climatology using cluster analysis
B. de Foy1,2, J. D. Fast3, S. J. Paech4, D. Phillips4, J. T. Walters4, R. L. Coulter5, T. J. Martin5, M. S. Pekour3, W. J. Shaw3, P. P. Kastendeuch6, N. A. Marley7, A. Retama8, and L. T. Molina1,9
1Molina Center for Energy and the Environment, CA, USA
2Department of Earth and Atmospheric Sciences, Saint Louis University, USA
3Pacific Northwest National Laboratory, Richland, WA, USA
4National Space Science and Technology Center, University of Alabama in Huntsville, AL, USA
5Argonne National Laboratory, IL, USA
6Centre de Géochimie de la Surface, Université Louis Pasteur, Strasbourg, France
7Department of Chemistry, University of Arkansas at Little Rock, AK, USA
8Secretaría del Medio Ambiente, Gobierno del Distrito Federal, México
9Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, USA

Abstract. The MILAGRO field campaign was a multi-agency international collaborative project to evaluate the regional impacts of the Mexico City air pollution plume as a means of understanding urban impacts on the global climate. Mexico City lies on an elevated plateau with mountains on three sides and has complex mountain and surface-driven wind flows. This paper asks what the wind transport was in the basin during the field campaign and how representative it was of the climatology. Surface meteorology and air quality data, radiosoundings and radar wind profiler data were collected at sites in the basin and its vicinity. Cluster analysis is used to identify the dominant wind patterns both during the campaign and within the past 10 years of operational data from the warm dry season. Our analysis shows that March 2006 was representative of typical flow patterns experienced in the basin. Six episode types were identified for the basin scale circulation providing a way of interpreting atmospheric chemistry and particulate data collected during the campaign. Decoupling between surface winds and those aloft had a strong influence in leading to convection and poor air quality episodes. Hourly characterisation of wind circulation during the MILAGRO, MCMA-2003 and IMADA field campaigns will enable the comparisons of similar air pollution episodes and the evaluation of the impact of wind transport on measurements of the atmospheric chemistry taking place in the basin.

Citation: de Foy, B., Fast, J. D., Paech, S. J., Phillips, D., Walters, J. T., Coulter, R. L., Martin, T. J., Pekour, M. S., Shaw, W. J., Kastendeuch, P. P., Marley, N. A., Retama, A., and Molina, L. T.: Basin-scale wind transport during the MILAGRO field campaign and comparison to climatology using cluster analysis, Atmos. Chem. Phys. Discuss., 7, 13035-13076, doi:10.5194/acpd-7-13035-2007, 2007.
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