RACORO continental boundary layer cloud investigations. 2. Large-eddy simulations of cumulus clouds and evaluation with in-situ and ground-based observations
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Authors
Endo, Satoshi
Fridlind, Ann M.
Lin, Wuyin
Vogelmann, Andrew M.
Toto, Tami
Ackerman, Andrew S.
McFarquhar, Greg M.
Jackson, Robert C.
Jonsson, Haflidi H.
Liu, Yangang
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Advisors
Date of Issue
2015-06-19
Date
Publisher
American Geophysical Union
Language
en_US
Abstract
A 60 h 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 multimodal 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 cloud properties are found to be insensitive in this nonprecipitating case, but microphysical properties are especially sensitive to bulk microphysics supersaturation treatment and aerosol hygroscopicity.
Type
Article
Description
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 cloud 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.
The article of record as published may be found at http://dx.doi.org/10.1002/2014JD022525
The article of record as published may be found at http://dx.doi.org/10.1002/2014JD022525
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Sponsors
USDOE Office of Science (SC)
Funder
SC00112704
This research was supported by the U.S. Department of Energy Science Office of Biological and Environmental Research Program under the Earth System Modeling Program via the FASTER Project (http://www.bnl.gov/ faster/) and the Atmospheric System Research Program via DE-SC00112704.
This research was supported by the U.S. Department of Energy Science Office of Biological and Environmental Research Program under the Earth System Modeling Program via the FASTER Project (http://www.bnl.gov/ faster/) and the Atmospheric System Research Program via DE-SC00112704.
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Citation
Endo, S., A. M. Fridlind, W. Lin,
A. M. Vogelmann, T. Toto, A. S. Ackerman, G. M. McFarquhar, R. C. Jackson,
H. H. Jonsson, and Y. Liu (2015), RACORO continental boundary layer cloud investigations: 2. Large-eddy simulations of cumulus clouds and evaluation with in situ and ground-based observations, J. Geophys. Res. Atmos., 120, 5993–6014, doi:10.1002/ 2014JD022525.
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.