Aerosol absorption measurement using photoacoustic spectroscopy: Sensitivity, calibration, and uncertainty developments

Light absorption by aerosols is one of the most uncertain parameters associated with the direct and indirect aerosol effects on climate and is one of the most difficult quantities to measure. This article describes the development of a sensitive method of measuring aerosol absorption at 532 nm with excellent time response (detection limit: 0.08 Mm(-1), 60 second average) using photoacoustic absorption spectroscopy. An accurate calibration method (accuracy of 1-2%) at atmospherically relevant absorption levels and independent validation of the photoacoustic technique is presented. An upper limit to the instrument precision for aerosol absorption measurement is approximate to 6% (2 sigma, 30 sec) while instrument accuracy is calculated to be approximate to 5%. A standard for aerosol absorption measurement techniques using well characterized absorbing aerosol is also proposed.