1Department of Earth and Atmospheric Sciences, Saint Louis University, St. Louis, MO, USA
2Molina Center for Energy and the Environment, La Jolla, CA, USA
3Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
4Aerodyne Research Inc., Billerica, MA, USA
5Georgia Institute of Technology, Atlanta, GA, USA
6General Direction of the National Center for Environmental Research and Training (CENICA), National Institute of Ecology (INE), Mexico
7Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, Mexico
Abstract. Large sulfur dioxide plumes were measured in the Mexico City Metropolitan Area (MCMA) during the MILAGRO field campaign. This paper seeks to identify the sources of these plumes and the meteorological processes that affect their dispersion in a complex mountain basin. Surface measurements of SO2 and winds are analysed in combination with radar wind profiler data to identify transport directions. Satellite retrievals of vertical SO2 columns from the Ozone Monitoring Instrument (OMI) reveal the dispersion from both the Tula industrial complex and the Popocatepetl volcano. Numerical simulations are used to identify possible transport scenarios. The analysis suggests that both Tula and Popocatepetl contribute to SO2 levels in the MCMA, sometimes on the same day due to strong vertical wind shear. The evaluation of simulations with known sources and pollutants suggests that the combination of observations and meteorological models will be useful in identifying sources and transport processes of other plumes observed during MILAGRO.