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observation of the spectrally invariant properties of clouds in cloudy-to-clear transition zones during the magic field campaignWe use the spectrally invariant method to study the variability of cloud optical thickness τau and droplet effective radius r(sub eff) in transition zones (between the cloudy and clear sky columns) observed from Solar Spectral Flux Radiometer (SSFR) and Shortwave Array Spectroradiometer-Zenith (SASZe) during the Marine ARM GPCI Investigation of Clouds (MAGIC) field campaign. The measurements from the SSFR and the SASZe are different, however inter-instrument differences of self-normalized measurements (divided by their own spectra at a fixed time) are small. The spectrally invariant method approximates the spectra in the cloud transition zone as a linear combination of definitely clear and cloudy spectra, where the coefficients, slope and intercept, characterize the spectrally invariant properties of the transition zone. Simulation results from the SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model demonstrate that (1) the slope of the visible band is positively correlated with the cloud optical thickness τ while the intercept of the near-infrared band has high negative correlation with the cloud drop effective radius r(sub eff)even without the exact knowledge of τau; (2) the above relations hold for all Solar Zenith Angle (SZA) and for cloud-contaminated skies. In observations using redundant measurements from SSFR and SASZe, we find that during cloudy-to-clear transitions, (a) the slopes of the visible band decrease, and (b) the intercepts of the near-infrared band remain almost constant near cloud edges. The findings in simulations and observations suggest that, while the optical thickness decreases during the cloudy-to-clear transition, the cloud drop effective radius does not change when cloud edges are approached. These results support the hypothesis that inhomogeneous mixing dominates near cloud edges in the studied cases.
Document ID
Document Type
Reprint (Version printed in journal)
Yang, Weidong
(Universities Space Research Association Columbia, MD, United States)
Marshak, Alexander
(NASA Goddard Space Flight Center Greenbelt, MD United States)
McBride, Patrick
(Atmospheric and Space Technology Research Associates Boulder, CO, United States)
Chiu, J. Christine
(Reading Univ. United Kingdom)
Knyazikhin, Yuri
(Boston Univ. Boston, MA, United States)
Schmidt, K. Sebastian
(Colorado Univ. Boulder, CO, United States)
Flynn, Connor
(Pacific Northwest National Lab. Richland, WA, United States)
Lewis, Ernie R.
(Brookhaven National Lab. Upton, NY, United States)
Eloranta, Edwin W.
(Wisconsin Univ. Madison, WI, United States)
Date Acquired
November 8, 2016
Publication Date
August 11, 2016
Publication Information
Publication: Atmospheric Research
Volume: 182
ISSN: 0169-8095
Subject Category
Meteorology and Climatology
Report/Patent Number
Funding Number(s)
Distribution Limits
spectral invariance
cloud-aerosol interactions
transition zone