HR: 11:35h
AN: A32A-06    [Abstracts]
TI: Ultraviolet Characteristics of PBL Aerosol in Mexico City
AU: * Madronich, S
EM: sasha@ucar.edu
AF: National Center for Atmospheric Research, P.O.Box 3000, Boulder, CO 80307, United States
AU: Shetter, R
EM: shetter@ucar.edu
AF: National Center for Atmospheric Research, P.O.Box 3000, Boulder, CO 80307, United States
AU: Hall, S
EM: halls@ucar.edu
AF: National Center for Atmospheric Research, P.O.Box 3000, Boulder, CO 80307, United States
AU: Lefer, B
EM: blefer@uh.edu
AF: U. of Houston, Dept. of Geosciences, Houston, TX 77204, United States
AU: Slusser, J
EM: sluss@uvb.nrel.colostate.edu
AF: Colorado State U., Natural Resource Ecology Laboratory, Fort Collins, CO 80523, United States
AB: The optical properties of aerosols are relatively unknown at ultraviolet wavelengths (UV, 280-400 nm in the troposphere), and may be quite different than those at the better-studied visible wavelengths. The UV band has a direct effect on atmospheric photochemistry and surface exposures of biota, so that perturbation to the natural UV radiation field may be quite important, especially in regions experiencing heavy aerosol loading. Here, we use data from the MILAGRO campaign (Mexico City, March 2006) to examine spectrally-resolved properties of an aerosol layer. Specifically, we compare spectral (280-420 nm, 1 nm FWHM resolution) actinic fluxes observed at the surface (the MILAGRO T1 supersite) with down-welling and up-welling spectral actinic fluxes measured from the C-130 aircraft during T1 overpasses. Ancillary observations includes ground based radiation (MFRSR, UV- MFRSR, AERONET); ground- and aircraft-based lidars, gaseous absorbers (O3, NO2, SO2), and in-situ aerosol properties; a few vertical profiles of O3 from tethered balloons and ozone sondes; and satellite-based measurements of O3, NO2, and aerosols. These observations, combined with the Tropospheric Ultraviolet- Visible (TUV) model, allow estimation of the transmission and reflection of the aerosol layer below the aircraft, as well as the ground albedo, all spectrally resolved over the UV wavelengths. A major question to be examined is whether the UV properties (e.g. single scattering albedo) can be estimated by Mie-guided extrapolation from visible wavelengths, or whether UV-specific absorbers are present (e.g., from chromophores associated with secondary organic aerosols).
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0360 Radiation: transmission and scattering
DE: 3355 Regional modeling
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting