Spectral absorption properties of aerosol particles from 350-2500nm L13810

Abstract

The aerosol spectral absorption efficiency (αa in m 2/g) is measured over an extended wavelength range (350-2500 nm) using an improved calibrated and validated reflectance technique and applied to urban aerosol samples from Sao Paulo, Brazil and from a site in Virginia, Eastern US, that experiences transported urban/industrial aerosol. The average αa values (∼3m2/g at 550 nm) for Sao Paulo samples are 10 times larger than αa values obtained for aerosols in Virginia. Sao Paulo aerosols also show evidence of enhanced UV absorption in selected samples, probably associated with organic aerosol components. This extra UV absorption can double the absorption efficiency observed from black carbon alone, therefore reducing by up to 50% the surface UV fluxes, with important implications for climate, UV photolysis rates, and remote sensing from space. Copyright 2009 by the American Geophysical Union.