TY - JOUR
T1 - Above-cloud aerosol radiative effects based on ORACLES 2016 and ORACLES 2017 aircraft experiments
AU - Cochrane, Sabrina P.
AU - Sebastian Schmidt, K.
AU - Chen, Hong
AU - Pilewskie, Peter
AU - Kittelman, Scott
AU - Redemann, Jens
AU - Leblanc, Samuel
AU - Pistone, Kristina
AU - Kacenelenbogen, Meloë
AU - Segal Rozenhaimer, Michal
AU - Shinozuka, Yohei
AU - Flynn, Connor
AU - Platnick, Steven
AU - Meyer, Kerry
AU - Ferrare, Rich
AU - Burton, Sharon
AU - Hostetler, Chris
AU - Howell, Steven
AU - Freitag, Steffen
AU - Dobracki, Amie
AU - Doherty, Sarah
N1 - Publisher Copyright:
© 2020 BMJ Publishing Group. All rights reserved.
PY - 2019/12/9
Y1 - 2019/12/9
N2 - Determining the direct aerosol radiative effect (DARE) of absorbing aerosols above clouds from satellite observations alone is a challenging task, in part because the radiative signal of the aerosol layer is not easily untangled from that of the clouds below. In this study, we use aircraft measurements from the NASA ObseRvations of CLouds above Aerosols and their intEractionS (ORACLES) project in the southeastern Atlantic to derive it with as few assumptions as possible. This is accomplished by using spectral irradiance measurements (Solar Spectral Flux Radiometer, SSFR) and aerosol optical depth (AOD) retrievals (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research, 4STAR) during vertical profiles (spirals) that minimize the albedo variability of the underlying cloud field - thus isolating aerosol radiative effects from those of the cloud field below. For two representative cases, we retrieve spectral aerosol single scattering albedo (SSA) and the asymmetry parameter (g) from these profile measurements and calculate DARE given the albedo range measured by SSFR on horizontal legs above clouds. For mid-visible wavelengths, we find SSA values from 0.80 to 0.85 and a significant spectral dependence of g. As the cloud albedo increases, the aerosol increasingly warms the column. The transition from a cooling to a warming top-of-aerosol radiative effect occurs at an albedo value (critical albedo) just above 0.2 in the mid-visible wavelength range. In a companion paper, we use the techniques introduced here to generalize our findings to all 2016 and 2017 measurements and parameterize aerosol radiative effects.
AB - Determining the direct aerosol radiative effect (DARE) of absorbing aerosols above clouds from satellite observations alone is a challenging task, in part because the radiative signal of the aerosol layer is not easily untangled from that of the clouds below. In this study, we use aircraft measurements from the NASA ObseRvations of CLouds above Aerosols and their intEractionS (ORACLES) project in the southeastern Atlantic to derive it with as few assumptions as possible. This is accomplished by using spectral irradiance measurements (Solar Spectral Flux Radiometer, SSFR) and aerosol optical depth (AOD) retrievals (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research, 4STAR) during vertical profiles (spirals) that minimize the albedo variability of the underlying cloud field - thus isolating aerosol radiative effects from those of the cloud field below. For two representative cases, we retrieve spectral aerosol single scattering albedo (SSA) and the asymmetry parameter (g) from these profile measurements and calculate DARE given the albedo range measured by SSFR on horizontal legs above clouds. For mid-visible wavelengths, we find SSA values from 0.80 to 0.85 and a significant spectral dependence of g. As the cloud albedo increases, the aerosol increasingly warms the column. The transition from a cooling to a warming top-of-aerosol radiative effect occurs at an albedo value (critical albedo) just above 0.2 in the mid-visible wavelength range. In a companion paper, we use the techniques introduced here to generalize our findings to all 2016 and 2017 measurements and parameterize aerosol radiative effects.
UR - http://www.scopus.com/inward/record.url?scp=85069482932&partnerID=8YFLogxK
U2 - 10.5194/amt-12-6505-2019
DO - 10.5194/amt-12-6505-2019
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AN - SCOPUS:85069482932
SN - 1867-1381
VL - 12
SP - 6505
EP - 6528
JO - Atmospheric Measurement Techniques
JF - Atmospheric Measurement Techniques
IS - 12
ER -