HR: 16:45h
AN: A14B-04    [Abstracts]
TI: Parameterization for the Relative Humidity Dependence of Aerosol Optical Properties
AU: * Baynard, T
EM: tbaynard@al.noaa.gov
AF: National Oceanic and Atmospheric Administration, 325 S. Broadway, Boulder, CO 80305 United States
AU: * Baynard, T
EM: tbaynard@al.noaa.gov
AF: Cooperative Institute for Research in the Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Garland, R
A14B-04 AF: Cooperative Institute for Research in the Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Garland, R
A14B-04 AF: Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309
AU: Lovejoy, E E
A14B-04 AF: National Oceanic and Atmospheric Administration, 325 S. Broadway, Boulder, CO 80305 United States
AU: Quinn, P
A14B-04 AF: National Oceanic and Atmospheric Administration - PMEL, 7600 Sand Point Way NE, Seattle, CO 98115
AU: Pettersson, A
A14B-04 AF: National Oceanic and Atmospheric Administration, 325 S. Broadway, Boulder, CO 80305 United States
AU: Pettersson, A
A14B-04 AF: Cooperative Institute for Research in the Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Bates, T
A14B-04 AF: National Oceanic and Atmospheric Administration - PMEL, 7600 Sand Point Way NE, Seattle, CO 98115
AU: Tolbert, M A
A14B-04 AF: Cooperative Institute for Research in the Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Tolbert, M A
A14B-04 AF: Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309
AU: Osthoff, H
A14B-04 AF: National Oceanic and Atmospheric Administration, 325 S. Broadway, Boulder, CO 80305 United States
AU: Osthoff, H
A14B-04 AF: Cooperative Institute for Research in the Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Ravishankara, A
A14B-04 AF: National Oceanic and Atmospheric Administration, 325 S. Broadway, Boulder, CO 80305 United States
AU: Ravishankara, A
A14B-04 AF: Cooperative Institute for Research in the Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Ravishankara, A
A14B-04 AF: Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309
AB: The significant influence of relative humidity (RH) on the mass scattering efficiency, f_σ(sp)(RH), and mass absorption efficiency, f_σ(ap)(RH), of atmospheric aerosol requires RH to be considered in radiative transfer calculations and currently is a large source of uncertainty. Possible factors influencing the RH dependence of f_σ(sp)(RH) include aerosol size, composition, and mixing state. A valid simple parameterization for the RH dependence is important to decrease uncertainty in both the direct and indirect aerosol effect. Using laboratory studies we have identified the key factors influencing the RH dependence. Considering these factors simultaneously through model calculations we have estimated the variability of f_σ(sp)(RH) in the atmosphere and provided a useful parameterization of f_σ(sp)(RH). Field measurements of the RH dependence of mass extinction efficiency, f_σ(ep)(RH), on composition obtained during NEAQS-ITCT 2004 using cavity ring-down aerosol extinction spectroscopy (CRD-AES) and aerosol mass spectrometry (AMS), help validate this approach. This presentation will include (a) identification of the key features allowing parameterization of f_σ(sp)(RH), (b) parameterization with respect to composition and size, and (c) comparison of this parameterization to other estimates of the RH dependence.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0360 Radiation: transmission and scattering
DE: 0365 Troposphere: composition and chemistry
DE: 1610 Atmosphere (0315, 0325)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005