Abstract
The principle, technical details, and performance of the long
path extinction spectrometer (LOPES), a new folded-path extinction
cell with a spectral range from the mid-UV (200 nm) to the
near infrared (1015 nm), is presented. Using nonabsorbing glass
beads the measured extinction spectrum of LOPES was validated
by Mie calculations and was compared with scattering coefficients
in the visible measured by a three-color integrating nephelometer
(TSI, mod. 3563). For absorbing aerosols (here soot and biomass
burning aerosol with single-scattering albedos of about 0.2 and
0.74 at 550 nm), LOPES was combined with a TSI 3563 nephelometer
to determine the wavelength-dependent absorption coefficients
from the difference of the extinction and scattering coefficients.
These absorption coefficients were found to agree with the measurements by two state-of-the-art absorption techniques, the multiangle absorption photometry (MAAP) and photoacoustic spectrometry (PAS), which measure the absorption coefficient at the single wavelength of 532 nm and 670 nm, respectively. Finally, based on a comprehensive analysis of the TSI 3563 nephelometer errors and their propagation into the determination of the absorption coefficients from the LOPES and nephelometer data, we discuss implications for improving in situmeasurements of the optical properties of atmospheric aerosols.