Article
Aerosol optical properties in the southeastern United States in summer - Part 1: Hygroscopic growth Public Deposited
https://scholar.colorado.edu/concern/articles/q524jp59d
- Abstract
- Aircraft observations of meteorological, trace gas, and aerosol properties were made during May–September 2013 in the southeastern United States (US) under fair-weather, afternoon conditions with well-defined planetary boundary layer structure. Optical extinction at 532 nm was directly measured at relative humidities (RHs) of ∼ 15, ∼ 70, and ∼ 90 % and compared with extinction calculated from measurements of aerosol composition and size distribution using the κ-Köhler approximation for hygroscopic growth. The calculated enhancement in hydrated aerosol extinction with relative humidity, f(RH), calculated by this method agreed well with the observed f(RH) at ∼ 90 % RH. The dominance of organic aerosol, which comprised 65 ± 10 % of particulate matter with aerodynamic diameter < 1 µm in the planetary boundary layer, resulted in relatively low f(RH) values of 1.43 ± 0.67 at 70 % RH and 2.28 ± 1.05 at 90 % RH. The subsaturated κ-Köhler hygroscopicity parameter κ for the organic fraction of the aerosol must have been < 0.10 to be consistent with 75 % of the observations within uncertainties, with a best estimate of κ = 0.05. This subsaturated κ value for the organic aerosol in the southeastern US is broadly consistent with field studies in rural environments. A new, physically based, single-parameter representation was developed that better described f(RH) than did the widely used gamma power-law approximation.
- Creator
- Date Issued
- 2016-04-22
- Academic Affiliation
- Journal Title
- Journal Issue/Number
- 8.0
- Journal Volume
- 16.0
- Last Modified
- 2019-12-06
- Resource Type
- Rights Statement
- DOI
- ISSN
- 1680-7316
- Language
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aerosolOpticalPropertiesInTheSoutheasternUnitedStatesInS.pdf | 2019-12-06 | Public | Download |