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Airborne observations of aerosol extinction by in situ and remote‐sensing techniques: Evaluation of particle hygroscopicity
Author(s) -
Ziemba Luke D.,
Lee Thornhill K.,
Ferrare Rich,
Barrick John,
Beyersdorf Andreas J.,
Chen Gao,
Crumeyrolle Suzanne N.,
Hair John,
Hostetler Chris,
Hudgins Charlie,
Obland Michael,
Rogers Raymond,
Scarino Amy Jo,
Winstead Edward L.,
Anderson Bruce E.
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2012gl054428
Subject(s) - aerosol , remote sensing , environmental science , in situ , relative humidity , lidar , satellite , extinction (optical mineralogy) , molar absorptivity , atmospheric sciences , meteorology , physics , optics , geology , astronomy
Extensive profiling of aerosol optical, chemical, and microphysical properties was performed in the Washington DC/Baltimore MD region in July 2011 during NASA DISCOVER‐AQ. In situ extinction coefficient ( σ ext,in‐situ ) measurements were made aboard the NASA P3‐B aircraft coincident with remote‐sensing observations by the High‐Spectral Resolution Lidar (HSRL; σ ext,HSRL ) aboard the NASA UC‐12 aircraft. A statistical comparison revealed good agreement within instrumental uncertainty ( σ ext,in‐situ = 1.1 σ ext,HSRL − 3.2 Mm −1 , r 2 = 0.88) and demonstrated the robust nature of hygroscopicity measurements (f(RH)) necessary to correct observations at dry relative humidity (RH) to ambient conditions. The average liquid‐water contribution to ambient visible‐light extinction was as much as 43% in this urban region. f(RH) values were observed to vary significantly from 1.1 to 2.1 on a day‐to‐day basis suggesting influence from both local and transported sources. Results emphasize the importance of accounting for the RH dependence of optical‐ and mass‐based aerosol air‐quality measurements (e.g., of PM 2.5 ), especially in relation to satellite and remote‐sensing retrievals.