Abstract
Abstract. Absorption photometers for real time application have been available since the 1980s, but the use of filter-based instruments to derive information on aerosol properties (absorption coefficient and black carbon, BC) is still a matter of debate. Several workshops have been conducted to investigate the performance of individual instruments over the intervening years. Two workshops with large sets of aerosol absorption photometers were conducted in 2005 and 2007. The data from these instruments were corrected using existing methods before further analysis. The inter-comparison shows a large variation between the responses to absorbing aerosol particles for different types of instruments. The unit to unit variability between instruments can be up to 30% for Particle Soot Absorption Photometers (PSAPs) and Aethalometers. Multi Angle Absorption Photometers (MAAPs) showed a variability of less than 5%. Reasons for the high variability were identified to be variations in sample flow and spot size. It was observed that different flow rates influence system performance with respect to response to absorption and instrumental noise. Measurements with non absorbing particles showed that the current corrections of a cross sensitivity to particle scattering are not sufficient. Remaining cross sensitivities were found to be a function of the total particle load on the filter. The large variation between the response to absorbing aerosol particles for different types of instruments indicates that current correction functions for absorption photometers are not adequate.
Highlights
Aerosols influence the radiation balance of the Earth through scattering and absorption of solar radiation
For GAW2005 the relative sensitivities are significantly smaller for both Particle Soot Absorption Photometers (PSAPs) and Aethalometer
Absorption coefficients were in a moderate range from 8 to 15 Mm−1 (GAW2005) and from 12 to 23 Mm−1 (EUSAAR2007)
Summary
Aerosols influence the radiation balance of the Earth through scattering and absorption of solar radiation. Other problems include ill-defined spectral sensitivities for certain types of instruments, drift of flow, spot sizes that deviate from those provided by manufacturers, etc Since all these factors affect the results of the measurement, they need to be well-characterized and corrected for. Results are presented from two absorption photometer workshops which were conducted in 2005 and 2007 at IfT (Leibniz Institute for Tropospheric Research) Leipzig, Germany The first of these workshops was held in the framework of WMO Global Atmosphere Watch (GAW) and in collaboration with the EU FP6 Network of Excellence ACCENT (Atmospheric Composition Change: A European Network) in 2005.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
