Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 5 2008 10.5194/acp-8-1209-2008 http://www.atmos-chem-phys.net/8/1209/2008/ http://www.atmos-chem-phys.net/8/1209/2008/acp-8-1209-2008.html http://www.atmos-chem-phys.net/8/1209/2008/acp-8-1209-2008.pdf 1209 1224 2008-03-03 Basin-scale wind transport during the MILAGRO field campaign and comparison to climatology using cluster analysis B. de Foy bdefoy@slu.edu J. D. Fast S. J. Paech D. Phillips J. T. Walters R. L. Coulter T. J. Martin M. S. Pekour W. J. Shaw P. P. Kastendeuch N. A. Marley A. Retama L. T. Molina Molina Center for Energy and the Environment, CA, USA Department of Earth and Atmospheric Sciences, Saint Louis University, USA Pacific Northwest National Laboratory, Richland, WA, USA National Space Science and Technology Center, University of Alabama in Huntsville, AL, USA Argonne National Laboratory, IL, USA Centre de Géochimie de la Surface, Université Louis Pasteur, Strasbourg, France Department of Chemistry, University of Arkansas at Little Rock, AK, USA Secretaría del Medio Ambiente, Gobierno del Distrito Federal, México Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, USA 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, radiosondes and radar wind profiler data were collected at sites in the basin and its vicinity. Cluster analysis was 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. 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