HR: 08:00h
AN: A31D-01    [Abstracts]
TI: LIDAR Observations of the Vertical Ozone and Aerosol Distribution over Mexico City during the MCMA-2003 Field Campaign
AU: * Simeonov, V
EM: valentin.simeonov@epfl.ch
AF: Laboratory of Air and Soil Pollution, Swiss Federal Technology, Lausanne (EPFL), Lausanne, 1015 Switzerland
AU: Ristori, P
AF: Laboratory of Air and Soil Pollution, Swiss Federal Technology, Lausanne (EPFL), Lausanne, 1015 Switzerland
AU: Taslakov, M
AF: Laboratory of Air and Soil Pollution, Swiss Federal Technology, Lausanne (EPFL), Lausanne, 1015 Switzerland
AU: Dinoev, T
AF: Laboratory of Air and Soil Pollution, Swiss Federal Technology, Lausanne (EPFL), Lausanne, 1015 Switzerland
AU: van den Bergh, H
AF: Laboratory of Air and Soil Pollution, Swiss Federal Technology, Lausanne (EPFL), Lausanne, 1015 Switzerland
AU: Frey, S
AF: Departments of Earth, Atmospheric and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States
AU: Molina, L T
AF: Departments of Earth, Atmospheric and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States
AU: Molina, M J
AF: Departments of Earth, Atmospheric and Planetary Sciences and of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 United States
AB: An international field measurement campaign was held in April - May 2003 in the Mexico City Metropolitan Area (MCMA) as part of an effort to understand the complex urban air pollution problems in large cities. Gas phase and aerosol constituents were studied intensively during the campaign. LIDAR played an important role for measuring boundary layer dynamics and photochemical processes by monitoring the vertical distribution of aerosols and ozone. Two elastic DIAL and one Raman DIAL for ozone measurements were operated quasi-simultaneously during the campaign at the CENICA super site. The lidar of the Swiss Federal Institute of Technology, Lausanne (EPFL), Switzerland is an elastic three-wavelength UV DIAL combined with an aerosol lidar at 532 nm with an operational range of 200-6000 m for ozone measurements and 200-10000 m for aerosol measurements. The other elastic system is a commercial, stand alone two-wavelength DIAL produced and operated by ELIGHT Laser Systems GmbH. It performed ozone measurements from 400 to 2000 m. A combined Raman DIAL and aerosol Raman system was on loan from Freie Universit„t Berlin. This instrument was operated by the MIT team and provided ozone concentration from 350 to 2600 m and multicolor aerosol backscatter, Raman and depolarization. The campaign was designed to cover the height of the annual photochemical season. Rain episodes during the afternoons and the evenings at the beginning of the campaign caused discontinuity in the observation. Improved meteorological conditions from April 25 to May 3 made continuous measurements of all participating Lidars possible. A cloud-topped boundary layer (BL) was the frequently observed in the afternoon during this period. The top of the BL estimated from the aerosol measurements showed steady day-to-day increase, reaching altitudes of up to 4 km, comparable to the altitudes of the surrounding mountains. An obvious detachment of the top of the BL was also observed by the EPFL Lidar during the last two days of the campaign. The intercomparison of the ozone profiles measured with the three Lidar systems shows good agreement in the overlap regions. Steady increase in the daily values of ozone concentrations and the formation of a residual layer were clearly seen in the ozone time series. The detachment of the BL observed in the aerosol data was also present in the ozone time series. Elevated ozone concentrations measured at high altitudes were found together with relatively clean air masses in the altitude region 500-700 m AGL. Wind speed and wind direction measured simultaneously with a tethered balloon showed significant wind shear in this altitude range giving a possible reason for the lower ozone and aerosol concentrations in the 500-700 m region.
DE: 3359 Radiative processes
DE: 3307 Boundary layer processes
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting