Ambient and Laboratory Photoacoustic Measurements of Aerosol Light Absorption and Scattering from 355 Nm (new) to 1047 Nm

Madhu Gyawali Desert Research Institute
William Arnott University of Nevada Reno
Ramona Atherton University of Nevada
Ian Arnold University of Nevada
Rahul Zaveri Pacific Northwest National Laboratory
Chen Song Pacific Northwest National Laboratory

Category: Aerosol Properties

Working Group: Aerosol Life Cycle

We present in situ and filter-based multi-spectral measurements of aerosol light scattering and absorption by ambient aerosols carried out in Reno, Nevada during December 2009 and January 2010. We report new in situ photoacoustic and reciprocal optical characteristics of aerosol in the UV region (355 nm), as well as analysis of the simultaneous measurements at wavelengths 405 nm, 532 nm, 870 nm, and 1047 nm. Comparisons are presented for the spectra of aerosol collected on quartz fiber filters and analyzed with an optical spectrometer from 365 nm to 870 nm. Previous studies have shown that ''''brown'''' organic aerosols exhibit higher absorption towards the UV region. Although the UV region of the solar spectrum arriving at the Earth is only 12% of the total power, this part of the spectrum is vital to atmospheric photochemistry and the formation of aerosol mass that affects radiation transfer at all wavelengths. We present aerosol optical properties Ångström exponent of absorption and scattering, single-scattering albedo, and total extinction during strongly inverted and clean conditions. The absorption at 355 nm was found as high as 70 Mm-1 with scattering around 400 Mm-1. The comparison of the aerosol optics on strong temperature inversion days with that of California wild fires and of Mexico City indicates the closeness of the air pollution in these different events and locations. The wavelength dependence of the aerosol absorption from UV, visible, and infrared regions shows signatures of the presence of the significant amount of black carbon during the temperature inversion episodes. Laboratory calibrations with incense (strong brown carbon source), kerosene soot, and salt aerosol are also presented. This work is being carried out in preparation for the CARES project in summer 2010.

This poster will be displayed at ASR Science Team Meeting.