Aerosol optical properties in the southeastern United States in summer – Part 1: Hygroscopic growth
Item
Title (Dublin Core)
Aerosol optical properties in the southeastern United States in summer – Part 1: Hygroscopic growth
Description (Dublin Core)
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 <i>κ</i>-Köhler approximation for hygroscopic growth. The calculated enhancement in hydrated aerosol extinction with relative humidity, <i>f</i>(RH), calculated by this method agreed well with the observed <i>f</i>(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 <i>f</i>(RH) values of 1.43 ± 0.67 at 70 % RH and 2.28 ± 1.05 at 90 % RH. The subsaturated <i>κ</i>-Köhler hygroscopicity parameter <i>κ</i> 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 <i>κ</i> = 0.05. This subsaturated <i>κ</i> 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 <i>f</i>(RH) than did the widely used gamma power-law approximation.
Creator (Dublin Core)
Brock, Charles A.
Wagner, Nicholas L.
Anderson, Bruce E.
Attwood, Alexis R.
Beyersdorf, Andreas
Campuzano-Jost, Pedro
Carlton, Annmarie G.
Day, Douglas A.
Diskin, Glenn S.
Gordon, Timothy D.
Jimenez, Jose L.
Lack, Daniel A.
Liao, Jin
Markovic, Milos Z.
Middlebrook, Ann M.
Ng, Nga L.
Perring, Anne E.
Richardson, Matthews S.
Schwarz, Joshua P.
Washenfelder, Rebecca A.
Welti, Andre
Xu, Lu
Ziemba, Luke D.
Murphy, Daniel M.
Date (Dublin Core)
2018-09-10
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-16-4987-2016
https://acp.copernicus.org/articles/16/4987/2016/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
