HR: 16:15h
AN: A24A-02    [Abstracts]
TI: Measurements of Black Carbon Specific Absorption Made During the Mexico City Metropolitan Area Field Campaign of 2003
AU: * Ackerman, T
EM: ackerman@pnl.gov
AF: Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352 United States
AU: Barnard, J
EM: james.barnard@pnl.gov
AF: Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352 United States
AU: Kassianov, E
EM: evgueni.kassianov@pnl.gov
AF: Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352 United States
AU: Frey, S
EM: lidar@mit.edu
AF: Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: Molina, L
EM: ltmolina@mit.edu
AF: Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences 77 Massachusetts Ave, Cambridge, MA 02139 United States
AU: Molina, M
EM: mmolina@mit.edu
AF: Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences 77 Massachusetts Ave, Cambridge, MA 02139 United States
AB: An important quantity used to characterize the effect of black carbon (BC) on aerosol absorption is the BC specific absorption, defined as the absorption cross section per unit mass. Using data taken as part of the Mexico City Metropolitan Area (MCMA) field campaign of 2003, we determine the specific absorption of BC. Mexico City is an ideal place to study aerosols and BC for many reasons, including large BC emissions, the high altitude of the site, which increases the relative importance of aerosols (over molecular scattering) in determining the radiative fluxes, and periods of both high and low relative humidity. The specific absorption is calculated in two ways; the first uses single scattering albedos derived from spectral irradiance measurements, while the other method uses LIDAR returns and surface measurements of BC. The value we find is steady from day to day, and close to its "canonical" value of about 10 m2/g. This suggests that BC is internally mixed with the ambient aerosol (or exists as very fine particles in an external mixture).
DE: 3359 Radiative processes
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
DE: 0360 Transmission and scattering of radiation
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting