AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Toward In-Situ Characterization of Aerosol Optics with a Supercontinuum Light Source Covering Most of the Solar Spectrum
Ian Arnold, HANS MOOSMULLER, Noopur Sharma, Claudio Mazzoleni, Patrick Arnott, Desert Research Institute
Abstract Number: 735 Working Group: Instrumentation and Methods
Abstract The ongoing development of a novel Photoacoustic Aerosol Light Absorption and Albedo Spectrometer (PALAAS) for real time, in situ, first principle measurement of aerosol light absorption, scattering, and single scattering albedo spectra is discussed. This instrument utilizes a novel broadband supercontinuum light source covering the solar spectral range from 400 to 2000 nm for simultaneous measurement of aerosol light absorption and scattering coefficients and aerosol single scattering albedo. Initial work has demonstrated the use of this light source in combination with multiple bandpass filters for the measurement of absorption and scattering coefficients. Currently, we are working toward the simultaneous measurement in 32 spectral bands, thereby increasing the number of bands by about one order of magnitude over state-of-the-art three-wavelength photoacoustic instruments. Simultaneous absorption and scattering measurements in these 32 bands will be enabled by using prisms to (1) spatially separate the super continuum spectrum, (2) modulate each spectral band at an individual acoustic frequency with a custom optical chopper, (3) recombine the spectrum into a laser beam, and (4) send the laser beam through a photoacoustic resonator. Measurements of the scattering coefficient with a scattering sensor in the photoacoustic instrument and the absorption coefficient with the photoacoustic instrument can be achieved for all 32 wavelength bands simultaneously by decoding modulation frequencies with fast Fourier transform (FFT) analysis. This instrument will be used for characterizing carbonaceous aerosol optics, visibility impairment, and radiative forcing by providing real time, in situ, first principle measurements of aerosol light absorption, scattering, and albedo spectra covering most of the terrestrial solar spectrum.