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Title: Improving Parameterization of Entrainment Rate for Shallow Convection with Aircraft Measurements and Large-Eddy Simulation

This work examines the relationships of entrainment rate to vertical velocity, buoyancy, and turbulent dissipation rate by applying stepwise principal component regression to observational data from shallow cumulus clouds collected during the Routine AAF [Atmospheric Radiation Measurement (ARM) Aerial Facility] Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) field campaign over the ARM Southern Great Plains (SGP) site near Lamont, Oklahoma. The cumulus clouds during the RACORO campaign simulated using a large eddy simulation (LES) model are also examined with the same approach. The analysis shows that a combination of multiple variables can better represent entrainment rate in both the observations and LES than any single-variable fitting. Three commonly used parameterizations are also tested on the individual cloud scale. A new parameterization is therefore presented that relates entrainment rate to vertical velocity, buoyancy and dissipation rate; the effects of treating clouds as ensembles and humid shells surrounding cumulus clouds on the new parameterization are discussed. Physical mechanisms underlying the relationships of entrainment rate to vertical velocity, buoyancy and dissipation rate are also explored.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [2] ;  [4] ;  [5] ;  [4]
  1. Nanjing Univ. of Information Science and Technology, Nanjing (China); Chinese Academy of Sciences (CAS), Beijing (China); Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Univ. of California, San Diego, CA (United States); Tsinghua Univ., Beijing (China)
  4. Nanjing Univ. of Information Science and Technology, Nanjing (China)
  5. Institute of Plateau Meteorology, China Meteorological Administration, Chengdu (China)
Publication Date:
OSTI Identifier:
1239781
Report Number(s):
BNL--111645-2015-JA
Journal ID: ISSN 0022-4928; R&D Project: 2016-BNL-EE631EECA-Budg; KP1703020
Grant/Contract Number:
SC0012704
Type:
Accepted Manuscript
Journal Name:
Journal of the Atmospheric Sciences
Additional Journal Information:
Journal Volume: 73; Journal Issue: 2; Journal ID: ISSN 0022-4928
Publisher:
American Meteorological Society
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
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES Entrainment rate; cumulus; dynamics; thermodynamics