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Title: Observation of the spectrally invariant properties of clouds in cloudy-to-clear transition zones during the MAGIC field campaign

We use the spectrally invariant method to study the variability of cloud optical thickness τ and droplet effective radius r 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 eff even without the exact knowledge of τ; (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 findmore » 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. Furthermore, these results support the hypothesis that inhomogeneous mixing dominates near cloud edges in the studied cases.« less
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9]
  1. NASA, Goddard Space Flight Center, Greenbelt, MD (United States); Univ. Space Research Assoc., Columbia, MD (United States)
  2. NASA, Goddard Space Flight Center, Greenbelt, MD (United States)
  3. Atmospheric & Space Technology Research Assoc. (ASTRA), Boulder, CO (United States)
  4. Univ. of Reading, Reading (United Kingdom)
  5. Boston Univ., Boston, MA (United States)
  6. Univ. of Colorado, Boulder, CO (United States)
  7. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  8. Brookhaven National Lab. (BNL), Upton, NY (United States)
  9. Univ. of Wisconsin, Madison, WI (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0169-8095; R&D Project: 2016-BNL-EE630EECA-Budg; KP1701000
Grant/Contract Number:
SC00112704; SC0005457; SC0011666
Accepted Manuscript
Journal Name:
Atmospheric Research
Additional Journal Information:
Journal Volume: 182; Journal Issue: C; Journal ID: ISSN 0169-8095
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES; transition zone; cloud; cloud-aerosol interaction; air entrainment and mixing; spectral invariance; MAGIC field campaign
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1358819