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Measured Constraints on Cloud-Top Entrainment to Reduce Uncertainty of Non-Precipitating Stratocumulus Shortwave Radiative Forcing in the Southern Ocean
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  • Kevin Sanchez,
  • Greg Roberts,
  • Lynn M Russell,
  • Minghui Diao
Kevin Sanchez
Scripps Institution of Oceanography

Corresponding Author:kjsanche@ucsd.edu

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Greg Roberts
Centre National de la Recherche Scientifique
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Lynn M Russell
University of California, San Diego
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Minghui Diao
San Jose State University
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Stratocumulus cloud-top entrainment has a significant effect on cloud properties, but there are few observations quantifying its impact. Using explicit 0D parcel model simulations, initialized with below-cloud in-situ measurements, and validated with in-situ measurements of cloud properties, the shortwave cloud radiative forcing (SWCF) was reduced by up to 100 W m-2 by cloud-top entrainment in the Southern Ocean. The impact of entrainment-corrected SWCF is between 2 and 20 times that of changes in the aerosol particle concentration or updraft at cloud base. The variability in entrainment-corrected SWCF accounts for up to 50 W m-2 uncertainty in estimating cloud forcing. Measurements necessary for estimating the impact of entrainment on cloud properties can be constrained from existing airborne platforms and provide a first-order approximation for cloud radiative properties of non-precipitating stratocumulus clouds. These measurement-derived estimates of entrainment can be used to validate and improve parameterizations of entrainment in Global Climate Models.
16 Nov 2020Published in Geophysical Research Letters volume 47 issue 21. 10.1029/2020GL090513