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Title: Thermal chains and entrainment in cumulus updrafts, Part 2: Analysis of idealized simulations

Abstract

Research has suggested that the structure of deep convection often consists of a series of rising thermals, or “thermal chain”, which contrasts with existing conceptual models that are used to construct cumulus parameterizations. In this work, simplified theoretical expressions for updraft properties obtained in Part 1 of this study are used to develop a hypothesis explaining why this structure occurs. In this hypothesis, cumulus updraft structure is strongly influenced by organized entrainment below the updraft’s vertical velocity maximum. In a dry environment, this enhanced entrainment can locally reduce condensation rates and increase evaporation, thus eroding buoyancy. For moderate-to-large initial cloud radius R, this breaks up the updraft into a succession of discrete pulses of rising motion (i.e., a thermal chain). For small R, this leads to the structure of a single, isolated rising thermal. In contrast, moist environments are hypothesized to favor plume-like updrafts for moderate-to-large R. In a series of axisymmetric numerical cloud simulations, R and environmental relative humidity (RH) are systematically varied to test this hypothesis. Vertical profiles of fractional entrainment rate, passive tracer concentration, buoyancy, and vertical velocity from these runs agree well with vertical profiles calculated from the theoretical expressions in Part 1. Analysis of themore » simulations supports the hypothesized dependency of updraft structure on R and RH, that is, whether it consists of an isolated thermal, a thermal chain, or a plume, and the role of organized entrainment in driving this dependency. Additional 3-dimensional (3-D) turbulent cloud simulations are analyzed, and the behavior of these 3-D runs is qualitatively consistent with the theoretical expressions and axisymmetric simulations.« less

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Naval Postgraduate School, Monterey, CA (United States)
  2. National Center for Atmospheric Research, Boulder, CO (United States)
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  5. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
University Corporation for Atmospheric Research, Boulder, CO (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Brookhaven National Lab. (BNL), Upton, NY (United States); National Center for Atmospheric Research, Boulder, CO (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Atmospheric Radiation Measurement (ARM) Data Center
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER); National Center of Meteorology; National Science Foundation (NSF)
OSTI Identifier:
1657535
Alternate Identifier(s):
OSTI ID: 1706675; OSTI ID: 1735704; OSTI ID: 1775084; OSTI ID: 1786986
Report Number(s):
PNNL-SA-148683; BNL-220685-2020-JAAM
Journal ID: ISSN 0022-4928
Grant/Contract Number:  
SC0020104; SC0016476; SC0000246356; AGS-1841674; AC05-76RL01830; AC52-07NA27344; SC0012704
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the Atmospheric Sciences
Additional Journal Information:
Journal Volume: 77; Journal Issue: 11; Journal ID: ISSN 0022-4928
Publisher:
American Meteorological Society
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

Peters, John M., Morrison, Hugh, Varble, Adam C., Hannah, Walter M., and Giangrande, Scott E. Thermal chains and entrainment in cumulus updrafts, Part 2: Analysis of idealized simulations. United States: N. p., 2020. Web. https://doi.org/10.1175/jas-d-19-0244.1.
Peters, John M., Morrison, Hugh, Varble, Adam C., Hannah, Walter M., & Giangrande, Scott E. Thermal chains and entrainment in cumulus updrafts, Part 2: Analysis of idealized simulations. United States. https://doi.org/10.1175/jas-d-19-0244.1
Peters, John M., Morrison, Hugh, Varble, Adam C., Hannah, Walter M., and Giangrande, Scott E. Thu . "Thermal chains and entrainment in cumulus updrafts, Part 2: Analysis of idealized simulations". United States. https://doi.org/10.1175/jas-d-19-0244.1.
@article{osti_1657535,
title = {Thermal chains and entrainment in cumulus updrafts, Part 2: Analysis of idealized simulations},
author = {Peters, John M. and Morrison, Hugh and Varble, Adam C. and Hannah, Walter M. and Giangrande, Scott E.},
abstractNote = {Research has suggested that the structure of deep convection often consists of a series of rising thermals, or “thermal chain”, which contrasts with existing conceptual models that are used to construct cumulus parameterizations. In this work, simplified theoretical expressions for updraft properties obtained in Part 1 of this study are used to develop a hypothesis explaining why this structure occurs. In this hypothesis, cumulus updraft structure is strongly influenced by organized entrainment below the updraft’s vertical velocity maximum. In a dry environment, this enhanced entrainment can locally reduce condensation rates and increase evaporation, thus eroding buoyancy. For moderate-to-large initial cloud radius R, this breaks up the updraft into a succession of discrete pulses of rising motion (i.e., a thermal chain). For small R, this leads to the structure of a single, isolated rising thermal. In contrast, moist environments are hypothesized to favor plume-like updrafts for moderate-to-large R. In a series of axisymmetric numerical cloud simulations, R and environmental relative humidity (RH) are systematically varied to test this hypothesis. Vertical profiles of fractional entrainment rate, passive tracer concentration, buoyancy, and vertical velocity from these runs agree well with vertical profiles calculated from the theoretical expressions in Part 1. Analysis of the simulations supports the hypothesized dependency of updraft structure on R and RH, that is, whether it consists of an isolated thermal, a thermal chain, or a plume, and the role of organized entrainment in driving this dependency. Additional 3-dimensional (3-D) turbulent cloud simulations are analyzed, and the behavior of these 3-D runs is qualitatively consistent with the theoretical expressions and axisymmetric simulations.},
doi = {10.1175/jas-d-19-0244.1},
journal = {Journal of the Atmospheric Sciences},
number = 11,
volume = 77,
place = {United States},
year = {2020},
month = {10}
}

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Works referenced in this record:

A Benchmark Simulation for Moist Nonhydrostatic Numerical Models
journal, December 2002


Bubble theory of penetrative convection
journal, January 1953

  • Scorer, R. S.; Ludlam, F. H.
  • Quarterly Journal of the Royal Meteorological Society, Vol. 79, Issue 339
  • DOI: 10.1002/qj.49707933908

A Numerical Investigation of Cumulus Thermals
journal, October 2016

  • Hernandez-Deckers, Daniel; Sherwood, Steven C.
  • Journal of the Atmospheric Sciences, Vol. 73, Issue 10
  • DOI: 10.1175/JAS-D-15-0385.1

Precipitation development in a New Mexico thunderstorm
journal, October 1989

  • Raymond, D. J.; Blyth, A. M.
  • Quarterly Journal of the Royal Meteorological Society, Vol. 115, Issue 490
  • DOI: 10.1002/qj.49711549011

The ‘starting plume’ in neutral surroundings
journal, July 1962


A New Double-Moment Microphysics Parameterization for Application in Cloud and Climate Models. Part I: Description
journal, June 2005

  • Morrison, H.; Curry, J. A.; Khvorostyanov, V. I.
  • Journal of the Atmospheric Sciences, Vol. 62, Issue 6
  • DOI: 10.1175/JAS3446.1

Evidence for Tilted Toroidal Circulations in Cumulus
journal, June 2007

  • Damiani, Rick; Vali, Gabor
  • Journal of the Atmospheric Sciences, Vol. 64, Issue 6
  • DOI: 10.1175/JAS3941.1

Sticky Thermals: Evidence for a Dominant Balance between Buoyancy and Drag in Cloud Updrafts
journal, August 2015

  • Romps, David M.; Charn, Alexander B.
  • Journal of the Atmospheric Sciences, Vol. 72, Issue 8
  • DOI: 10.1175/JAS-D-15-0042.1

Buoyancy‐driven entrainment in dry thermals
journal, November 2019

  • McKim, Brett; Jeevanjee, Nadir; Lecoanet, Daniel
  • Quarterly Journal of the Royal Meteorological Society, Vol. 146, Issue 726
  • DOI: 10.1002/qj.3683

An Analytic Description of the Structure and Evolution of Growing Deep Cumulus Updrafts
journal, March 2017


The Dependence of Numerically Simulated Convective Storms on Vertical Wind Shear and Buoyancy
journal, June 1982


The Influence of Vertical Wind Shear on Moist Thermals
journal, May 2019

  • Peters, John M.; Hannah, Walter; Morrison, Hugh
  • Journal of the Atmospheric Sciences, Vol. 76, Issue 6
  • DOI: 10.1175/JAS-D-18-0296.1

Theoretical Expressions for the Ascent Rate of Moist Deep Convective Thermals
journal, May 2018

  • Morrison, Hugh; Peters, John M.
  • Journal of the Atmospheric Sciences, Vol. 75, Issue 5
  • DOI: 10.1175/JAS-D-17-0295.1

Simulations of Right- and Left-Moving Storms Produced Through Storm Splitting
journal, June 1978


The Influence of Successive Thermals on Entrainment and Dilution in a Simulated Cumulus Congestus
journal, February 2017

  • Moser, Daniel H.; Lasher-Trapp, Sonia
  • Journal of the Atmospheric Sciences, Vol. 74, Issue 2
  • DOI: 10.1175/JAS-D-16-0144.1

Entrainment versus Dilution in Tropical Deep Convection
journal, November 2017


Development of ice and precipitation in New Mexican summertime cumulus clouds
journal, January 1993

  • Blyth, Alan M.; Latham, John
  • Quarterly Journal of the Royal Meteorological Society, Vol. 119, Issue 509
  • DOI: 10.1002/qj.49711950905

A Direct Measure of Entrainment
journal, June 2010


Entrainment and detrainment in cumulus convection: an overview
journal, June 2012

  • de Rooy, Wim C.; Bechtold, Peter; Fröhlich, Kristina
  • Quarterly Journal of the Royal Meteorological Society, Vol. 139, Issue 670
  • DOI: 10.1002/qj.1959

Improved Madden–Julian Oscillations with Improved Physics: The Impact of Modified Convection Parameterizations
journal, February 2012

  • Zhou, Lei; B. Neale, Richard; Jochum, Markus
  • Journal of Climate, Vol. 25, Issue 4
  • DOI: 10.1175/2011JCLI4059.1

Stereo photogrammetry reveals substantial drag on cloud thermals: STEREO PHOTOGRAMMETRY OF CLOUD THERMALS
journal, June 2015

  • Romps, David M.; Öktem, Rusen
  • Geophysical Research Letters, Vol. 42, Issue 12
  • DOI: 10.1002/2015GL064009

Slippery Thermals and the Cumulus Entrainment Paradox*
journal, August 2013

  • Sherwood, Steven C.; Hernández-Deckers, Daniel; Colin, Maxime
  • Journal of the Atmospheric Sciences, Vol. 70, Issue 8
  • DOI: 10.1175/JAS-D-12-0220.1

Experiments on convection of isolated masses of buoyant fluid
journal, August 1957


The Structure of Thermals in Cumulus from Airborne Dual-Doppler Radar Observations
journal, May 2006

  • Damiani, Rick; Vali, Gabor; Haimov, Samuel
  • Journal of the Atmospheric Sciences, Vol. 63, Issue 5
  • DOI: 10.1175/JAS3701.1

Basic convective element: bubble or plume? A historical review
journal, January 2014


Thermal Chains and Entrainment in Cumulus Updrafts. Part I: Theoretical Description
journal, November 2020

  • Morrison, Hugh; Peters, John M.; Varble, Adam C.
  • Journal of the Atmospheric Sciences, Vol. 77, Issue 11
  • DOI: 10.1175/JAS-D-19-0243.1