HR: 16:30h
AN: A24A-03    [Abstracts]
TI: Evidence of NO2 Contamination of Aerosol Single Scattering Albedo Retrievals Made During the MCMA Field Campaign of 2003
AU: * Barnard, J
EM: james.barnard@pnl.gov
AF: Pacific Northwest National Laboratory, PO Pox 999, Richland, WA 99352 United States
AU: Kassianov, E
EM: evgueni.kassianov@pnl.gov
AF: Pacific Northwest National Laboratory, PO Pox 999, Richland, WA 99352 United States
AU: Volkamer, R
EM: rainer@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: Solar irradiance data from the Multi-Filter Rotating Shadowband Radiometer (MFRSR) deployed during the MCMA field campaign were used to derive aerosol single scattering albedos (SSA) for five wavelengths spanning the near-UV (415 nm) to the near-IR (870 nm). Plotting these SSAs versus wavelength shows that the SSA at 415 nm is anomalously low. It is doubtful that this anomaly can be explained by aerosol optical properties, and we hypothesize that it is caused by the absorption of solar radiation by nitrogen dioxide (NO2) in near-UV spectral region. This absorption is usually small, because of the low background concentrations of NO2 in the atmosphere, and is therefore usually neglected. However, DOAS measurements of NO2 revealed that its concentration is so large in the Mexico City basin that NO2 absorption can no longer be ignored when retrieving SSAs. Accounting for this absorption in the retrieval increases the SSA at 415 nm to values which are plausible. This finding supports the hypothesis that large NO2 absorption is contaminating SSAs retrievals at 415 nm and one must therefore consider this absorption under certain circumstances.
DE: 3359 Radiative processes
DE: 0345 Pollution--urban and regional (0305)
DE: 0360 Transmission and scattering of radiation
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting