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Retrievals of Aerosol Size Distribution, Spherical Fraction, and Complex Refractive Index From Airborne In Situ Angular Light Scattering and Absorption Measurements
Author(s) -
Espinosa W. Reed,
Martins J. Vanderlei,
Remer Lorraine A.,
Dubovik Oleg,
Lapyonok Tatyana,
Fuertes David,
Puthukkudy Anin,
Orozco Daniel,
Ziemba Luke,
Thornhill K. Lee,
Levy Robert
Publication year - 2019
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2018jd030009
Subject(s) - aerosol , nephelometer , scattering , absorption (acoustics) , refractive index , atmospheric sciences , chemistry , radiative transfer , analytical chemistry (journal) , environmental science , light scattering , computational physics , meteorology , optics , physics , chromatography
Aerosol models, composed of size distribution, complex refractive index, and spherical fraction, are derived from a new synergistic retrieval of airborne in situ angular scattering measurements made by the Polarized Imaging Nephelometer and absorption measurements from the Particle Soot Absorption Photometer. The data utilized include phase function ( F 11 ), degree of polarization (− F 12 / F 11 ), and absorption coefficient ( β a b s ) measured at low relative humidities during the Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC 4 RS) and Deep Convection Clouds and Chemistry (DC3) field campaigns. The Generalized Retrieval of Aerosol and Surface Properties (GRASP) is applied to these measurements to obtain summaries of particle properties that are optically consistent with the original measurements. A classification scheme is then used to categorize the corresponding retrieval results. Inversions performed on the DC3 measurements indicate the presence of a significant amount of dust‐like aerosol in the inflow of storms sampled during this campaign, with the quantity of dust present depending strongly on the underlying surface features. In the SEAC 4 RS data, the retrieved size distributions were found to be remarkably similar among a range of aerosol types, including urban and industrial, biogenic, and biomass burning (BB) emissions. These aerosol types were found to have average fine mode volume median radii 0.155 ≤ r v f ≤ 0.163μm and lognormal standard deviations 0.32 ≤ σ f ≤ 0.36. There were, however, consistent differences between the angular scattering patterns of the BB samples and the other particle types. The GRASP retrieval predominantly attributed these differences to elevated real and imaginary refractive indices in the BB samples ( m 532 n m ≈1.55+0.007 i ) relative to the two other categories ( m 532 n m ≈1.51+0.004 i ).