Monday, 3 June 2002: 10:30 AM
Measurements of absorption and scattering coefficients in marine, continental, and polluted air masses
Due to scattering and absorbing effects, atmospheric aerosols are of primary importance in controlling the amount of incoming radiation that reaches the surface. Aerosols can play an important role in climate change, causing atmospheric cooling or warming, especially on a regional scale. Aerosol scattering and absorption effects in the southeastern U.S. are measured for September 1999 at a regionally representative site, Mt. Gibbes, NC (35.78N, 82.29W, 2006m MSL). Scattering coefficient values are measured using a single wavelength nephelometer, and absorption coefficient values are measured using an aethalometer, which measures the amount of light attenuated by a sample. The scattering and absorption coefficient values are classified according to air mass type. Air mass origins are determined using 48 hour back trajectories obtained from the NOAA HYSPLIT (hybrid single-particle Lagrangian integrated trajectory model). Air masses arriving at the site have been classified as either continental, polluted, or marine, based on EPA emission inventories of SOx and NOx. The average scattering coefficients for each sector are 4.55 E-05 m-1 ± 5.35E-05 for marine air masses,1.16E-04 ± 1.06E-04 for polluted air masses, and 1.25E-04 ± 9.79E-05 for continental air masses. The average absorption coefficients for each sector are 4.69E-06 ± 3.38E-06 for marine air masses, 1.19E-05 ± 4.66E-06 for polluted air masses,and 1.02E-05 ± 4.74E-07 for continental air masses. A strong correlation is found between the measured scattering coefficient and absorbing coefficient, suggesting that the source of scattering and absorbing aerosols is the same.