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Title: RACORO continental boundary layer cloud investigations. 2. Large-eddy simulations of cumulus clouds and evaluation with in-situ and ground-based observations

A 60-hour case study of continental boundary layer cumulus clouds is examined using two large-eddy simulation (LES) models. The case is based on observations obtained during the RACORO Campaign (Routine Atmospheric Radiation Measurement [ARM] Aerial Facility [AAF] Clouds with Low Optical Water Depths [CLOWD] Optical Radiative Observations) at the ARM Climate Research Facility's Southern Great Plains site. The LES models are driven by continuous large-scale and surface forcings, and are constrained by multi-modal and temporally varying aerosol number size distribution profiles derived from aircraft observations. We compare simulated cloud macrophysical and microphysical properties with ground-based remote sensing and aircraft observations. The LES simulations capture the observed transitions of the evolving cumulus-topped boundary layers during the three daytime periods, and generally reproduce variations of droplet number concentration with liquid water content (LWC), corresponding to the gradient between the cloud centers and cloud edges at given heights. The observed LWC values fall within the range of simulated values; the observed droplet number concentrations are commonly higher than simulated, but differences remain on par with potential estimation errors in the aircraft measurements. Sensitivity studies examine the influences of bin microphysics versus bulk microphysics, aerosol advection, supersaturation treatment, and aerosol hygroscopicity. Simulated macrophysical cloudmore » properties are found to be insensitive in this non-precipitating case, but microphysical properties are especially sensitive to bulk microphysics supersaturation treatment and aerosol hygroscopicity.« less
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [3] ;  [4] ;  [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. NASA Goddard Inst. for Space Studies (GISS), New York, NY (United States)
  3. Univ. of Illinois, Urbana, IL (United States)
  4. Naval Postgraduate School, Monterey, CA (United States)
Publication Date:
OSTI Identifier:
1201350
Report Number(s):
BNL--108008-2015-JA
Journal ID: ISSN 2169-897X; R&D Project: 2016-BNL-EE631EECA-Budg; KP1703020
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research: Atmospheres
Additional Journal Information:
Journal Volume: 120; Journal Issue: 12; Journal ID: ISSN 2169-897X
Publisher:
American Geophysical Union
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES