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AGU: Journal of Geophysical Research, Atmospheres

 

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  • Atmospheric Composition and Structure: Aerosols and particles
  • Atmospheric Composition and Structure: Ion chemistry of the atmosphere
  • Atmospheric Composition and Structure: Middle atmosphere—composition and chemistry
Abstract
Cited By (19)
 

Abstract

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, 4279, 16 PP., 2003
doi:10.1029/2002JD002998

Humidity-dependent optical properties of fine particles during the Big Bend Regional Aerosol and Visibility Observational Study

William C. Malm

National Park Service-Air Resources Division, Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, Colorado, USA

Derek E. Day

Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, Colorado, USA

Sonia M. Kreidenweis

Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA

Jeffrey L. Collett

Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA

Taehyoung Lee

Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA

The Environmental Protection Agency (EPA) and National Park Service (NPS) initiated a comprehensive field experiment called The Big Bend Regional Aerosol and Visibility Observational Study (BRAVO) to investigate the source of visibility-reducing aerosols at Big Bend National Park, Texas. The study was carried out over a period of 4 months starting in the first week of July 1999. One objective of the study was to gain insight into the atmospheric light-scattering properties of ambient aerosols, especially as they relate to their hygroscopicity. This paper will report on comparisons between measured and modeled estimations of dry and ambient scattering and comparisons between measured and modeled ratios of wet and dry scattering, f(RH), as a function of relative humidity (RH). Two equilibrium models, exercised in combination with Mie scattering theory, were used to predict atmospheric aerosol water content and associated increase in atmospheric scattering. Modeled and measured deliquescence and crystallization points were also compared. Measured and modeled deliquescence were always within 10% RH while crystallization RHs were always within a few percentage points. The analysis suggests that on most days some water is retained by the aerosol at low RHs (20–30%) and in most cases the hygroscopic growth of only inorganic salts accounted for all the observed increase in scattering as a function of RH.

Published 10 May 2003.

Citation: Malm, W. C., D. E. Day, S. M. Kreidenweis, J. L. Collett, and T. Lee (2003), Humidity-dependent optical properties of fine particles during the Big Bend Regional Aerosol and Visibility Observational Study, J. Geophys. Res., 108(D9), 4279, doi:10.1029/2002JD002998.

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