The absorption coefficient was measured by monitoring the change in transmission through a filter with a Particle Soot Absorption Photometer (PSAP, Radiance Research) at less than 55% RH. Values are reported at 550 nm, 0°C, and 1013 mb. Measured values have been corrected for a scattering artifact, the deposit spot size, the PSAP flow rate, and the manufacturer's calibration as per Bond et al. .
Measurement RH: The sample air supplied to the PSAP was controlled to near 55% RH. The actual RH of the air inside the PSAP is expected to be lower, however, due to the PSAP location and heating within the PSAP.
Inlet: Two single-stage impactors, one with a D50,aero(55% RH) of 1.1 um and one with a D50,aero(55% RH) of 10 um were placed upstream of the PSAP. An automated valve switched between the two impactors every 15 minutes so that sampling alternated between sub-1 um and sub-10 um aerosol.
Averaging interval: 30 min
Time stamp: Decimal day of year where DOY 75.5 is noon on March 16th. Time given is the mid-point of the 30 min averaging interval.
Time period covered by data: DOY 75.1667 to 109.292 (March 16th - April 19th).
Bond, T.C., T.L. Anderson and D. Campbell. Calibration and intercomparison of filter-based measurements of visible light absorption by aerosols. Aerosol Sci and Technol., 30, 582-600, 1999.
Data can be downloaded in ACF format by following the ASCII link, or in binary netCDF file format by following the netCDF link