Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 4 2008 10.5194/acpd-8-12625-2008 http://www.atmos-chem-phys-discuss.net/8/12625/2008/ http://www.atmos-chem-phys-discuss.net/8/12625/2008/acpd-8-12625-2008.html http://www.atmos-chem-phys-discuss.net/8/12625/2008/acpd-8-12625-2008.pdf 12625 12663 2008-07-03 Measurements of aerosol absorption and scattering in the Mexico City Metropolitan Area during the MILAGRO field campaign: a comparison of results from the T0 and T1 sites N. A. Marley J. S. Gaffney jsgaffney@ualr.edu T. Castro A. Salcido J. Frederick Graduate Institute of Technology, University of Arkansas at Little Rock, Little Rock, AR, USA Department of Chemistry, University of Arkansas at Little Rock, Little Rock, AR, USA Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, México City, México Instituto de Investigaciones Eléctricas, Gerencia de Sistemas de Calidad Ambiente y Seguridad, Cuernavaca, Morelos, México Department of Geophysical Sciences, The University of Chicago, Chicago, IL, USA Measurements of aerosol absorption and scattering were obtained in Mexico City during the MILAGRO (Megacity Initiative: Local and Global Research Observations) field campaign in March 2006. A comparison of aerosol absorption and scattering was obtained in Mexico City at site T0 located in the northern part of Mexico City at the Instituto Mexicano del Petróleo Laboratories and at site T1 located at the Universidad Tecnológica de Tecamac, 18 miles northwest of T0. Hourly averages of aerosol absorption were similar at both sites, ranging from 6–93 Mm−1 with an average of 31 Mm−1 at T0; and from 2–104 Mm−1 with an average of 19 Mm−1 at T1. Aerosol scattering at T0 ranged from 16–344 Mm−1 with an average of 105 Mm−1; while the scattering values at T1 were lower than T0 ranging from 2–136 with an average of 53 Mm−1. Aerosol single scattering albedos (SSAs) were determined at both sites using these data. SSAs at T1 ranged from 0.44–0.90 with an average 0.75 as compared to hose at T0, range 0.51–0.93 with an average of 0.77. Broadband UV-B intensity was found to be higher at site T0, with an average of 64 μW/cm2 at solar noon, than at site T1, which had an average of 54 μW/cm2 at solar noon. Comparisons of clear-sky modeled UV-B intensities with the simultaneous UV-B measurements obtained at site T0 and at site T1 for cloudless days indicate a larger diffuse radiation field at site T0 than at site T1. 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