HR: 09:30h
AN: A41E-07    [Abstracts]
TI: Aerosol Light Absorption and Scattering at Four Sites in and Near Mexico City: Comparison with Las Vegas, Nevada, USA
AU: * Arnott, W P
EM: patarnott@physics.unr.edu
AF: Physics and Atmospheric Sciences University of Nevada Reno, Physics MS 220 UNR, Reno, NV 89557, United States
AU: Miranda, G P
EM: gparedes@physics.unr.edu
AF: Physics and Atmospheric Sciences University of Nevada Reno, Physics MS 220 UNR, Reno, NV 89557, United States
AU: Gaffney, J S
EM: jsgaffney@ualr.edu
AF: Chemistry Department University of Arkansas, University of Arkansas Chemistry 2801 South University Avenue SCLB RM 451, Little Rock, AR 72204, United States
AU: Marley, N A
EM: namarley@ualr.edu
AF: Chemistry Department University of Arkansas, University of Arkansas Chemistry 2801 South University Avenue SCLB RM 451, Little Rock, AR 72204, United States
AB: Four photoacoustic spectrometers (PAS) for aerosol light scattering and absorption measurements were deployed in and near Mexico City in March 2006 as part of the Megacity Impacts on Regional and Global Environments (MIRAGE). The four sites included: an urban site at Instituto Mexicano del Petroleo (Mexican Oil Institute, denoted by IMP); a suburban site at the Technological University of Tecamac; a rural site at "La Biznaga" ranch; and a site at the Paseo de Cortes (altitude 3,810 meters ASL) in the rural area above Amecameca in the State of Mexico, on the saddle between the volcanoes Popocatepetl and Iztaccihuatl. A similar campaign was held in Las Vegas, Nevada, USA in January-February, 2003. The IMP site gave in-situ characterization of the Mexico City plume under favorable wind conditions while the other sites provided characterization of the plume, mixed in with any local sources. The second and third sites are north of Mexico City, and the fourth site is south. The PAS used at IMP operates at 532 nm, and conveniently allowed for characterization of gaseous absorption at this wavelength as well. Instruments at the second and third sites operate at 870 nm, and the one at the fourth site at 780 nm. Light scattering measurements are accomplished within the PAS by the reciprocal nephelometery method. In the urban site the aerosol absorption coefficient typically varies between 20 and 180 Mm-1 during the course of the day and significant diurnal variation of the aerosol single scattering albedo was observed probably as a consequence of secondary aerosol formation. Comparisons with TSI nephelometer scattering at the T0 site will be presented. We will present the diurnal variation of the scattering and absorption as well as the single scattering albedo and fraction of absorption due to gases at the IMP site and compare with Las Vegas diurnal variation. Mexico City 'breaths' more during the course of the day than Las Vegas, Nevada in part because the latitude of Mexico City resulted in more direct solar radiation. Further insight on the meteorological connections will be discussed.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0360 Radiation: transmission and scattering
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly