Hygroscopic Properties and Wavelength Dependence of Light Extinction of Aerosols as measured by Cavity Ring-Down Spectrometry (CRD-AES) during the TeXAQS-GoMACCS 2006 study

HR: 1340h
AN: A43C-1424 [Abstracts]
TI: Hygroscopic Properties and Wavelength Dependence of Light Extinction of Aerosols as measured by Cavity Ring-Down Spectrometry (CRD-AES) during the TeXAQS-GoMACCS 2006 study
AU: * Massoli, P
EM: Paola.Massoli@noaa.gov
AF: CIRES, University of Colorado, Boulder, CO 80309, United States
AU: * Massoli, P
EM: Paola.Massoli@noaa.gov
AF: NOAA ESRL/CSD, 325 Broadway, Boulder, CO 80305, United States
AU: Baynard, T
EM: Tahllee.Baynard@comcast.net
AF: CIRES, University of Colorado, Boulder, CO 80309, United States
AU: Baynard, T
EM: Tahllee.Baynard@comcast.net
AF: NOAA ESRL/CSD, 325 Broadway, Boulder, CO 80305, United States
AU: Lack, D
EM: Daniel.Lack@noaa.gov
AF: CIRES, University of Colorado, Boulder, CO 80309, United States
AU: Lack, D
EM: Daniel.Lack@noaa.gov
AF: NOAA ESRL/CSD, 325 Broadway, Boulder, CO 80305, United States
AU: Bates, T
EM: Tim.Bates@noaa.gov
AF: NOAA PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States
AU: Quinn, P
EM: Patricia.K.Quinn@noaa.gov
AF: NOAA PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, United States
AU: Lovejoy, E
EM: Edward.R.Lovejoy@noaa.gov
AF: NOAA ESRL/CSD, 325 Broadway, Boulder, CO 80305, United States
AU: Brock, C
EM: Charles.A.Brock@noaa.gov
AF: CIRES, University of Colorado, Boulder, CO 80309, United States
AU: Brock, C
EM: Charles.A.Brock@noaa.gov
AF: NOAA ESRL/CSD, 325 Broadway, Boulder, CO 80305, United States
AU: Ravishankara, A
EM: A.R.Ravishankara@noaa.gov
AF: NOAA ESRL/CSD, 325 Broadway, Boulder, CO 80305, United States
AB: Light extinction coefficient, optical depth, single scattering albedo and asymmetry parameter are the key optical properties that determine the influence of aerosols on climate via scattering and absorption of incoming solar radiation, i.e., direct effect. These properties vary with the wavelength and are also strong function of the ambient relative humidity. Size and refractive index of aerosols can change significantly if the aerosols are hygroscopic. Accurate estimate of the relative humidity dependence of extinction is critical to properly quantify the effects of aerosols on climate and on visibility changes (i.e., air quality). A Cavity Ring-Down Aerosol Extinction Spectrometer (CRD-AES), developed at NOAA ESRL, was deployed on the RV R.H.Brown during the TEXAQS- GoMACCS 2006 study in the Gulf of Mexico to characterize the local and regional aerosols and to assess their impact on air quality and climate. Aerosol extinction at 355, 532, and 1064 nm for sub-1 micron and coarse size aerosols were measured at different relative humidity. Further, a Photoacoustic Absorption Spectrometer (PAS) that measures light absorption by aerosols was coupled to the CRD-AES to determine aerosol single scattering albedo at 532 nm. Here we present the humidity dependence (gamma), single scattering albedo and Angstrom exponent for a selection of aerosol types with varying chemical composition. Fresh local emissions (such as ship plumes and urban aerosols) appear to be hydrophobic, whereas regional and continental aerosols exhibit some variability, likely due to the degree of mixing and transformation during transport. These data are discussed with special emphasis on the proper treatment of the variation of the optical properties with relative humidity, critical for radiative models to better estimate the aerosol forcing on climate.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting