Preprints
https://doi.org/10.5194/egusphere-2024-2413
https://doi.org/10.5194/egusphere-2024-2413
05 Aug 2024
 | 05 Aug 2024

Warm-phase Microphysical Evolution in Large Eddy Simulations of Tropical Cumulus Congestus: Constraining Drop Size Distribution Evolution using Polarimetery Retrievals and a Thermal-Based Framework

McKenna Stanford, Ann Fridlind, Andrew Ackerman, Bastiaan van Diedenhoven, Qian Xiao, Jian Wang, Toshihisa Matsui, Daniel Hernandez-Deckers, and Paul Lawson

Abstract. Improving parameterizations of convective microphysics in Earth system models (ESMs) requires well-constrained cases suitable for scaling between cloud-resolving models and ESMs. We propose a benchmark large eddy simulation (LES) cumulus congestus case study from the NASA Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP2Ex) and demonstrate its observational constraints using novel polarimetric retrievals and in situ cloud microphysics measurements. Simulations using bulk and bin microphysics with observed aerosol input are compared to cloud-top retrievals of cloud droplet effective radius (Reff) and number concentration (Nd) from the airborne Research Scanning Polarimeter (RSP). The bulk scheme reasonably reproduces characteristic profiles of cloud-top Nd that decrease with altitude, while the bin simulation realizes greater discrepancies due to weaker precipitation formation. The Nd profile is strongly sensitive to the collision-coalescence process and the vertically resolved aerosol distribution, but appears well-constrained, whereas a persistent low-bias in Reff is evident in both schemes. Comparison of simulated and in situ droplet size distributions (DSDs) show that low-biased Reff originates from a cloud droplet mode that is too narrow relative to observations. Finally, a thermal-tracking framework demonstrates that the dilution of Nd throughout a thermal's lifetime is heavily determined by collision-coalescence and the height-varying aerosol distribution, and that in the absence of these, the impact of entrainment on diluting Nd is largely offset by continuous aerosol activation. Implications for developing warm-phase convective microphysics schemes for ESMs, evaluation of cumulus congestus using single column model versions of ESMs, and translating results to global, space-based polarimetry platforms are discussed.

Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics. The peer-review process was guided by an independent editor, and the authors also have no other competing interests to declare.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
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Journal article(s) based on this preprint

25 Sep 2025
Warm-phase microphysical evolution in large-eddy simulations of tropical cumulus congestus: evaluating drop size distribution evolution using polarimetry retrievals, in situ measurements, and a thermal-based framework
McKenna W. Stanford, Ann M. Fridlind, Andrew S. Ackerman, Bastiaan van Diedenhoven, Qian Xiao, Jian Wang, Toshihisa Matsui, Daniel Hernandez-Deckers, and Paul Lawson
Atmos. Chem. Phys., 25, 11199–11231, https://doi.org/10.5194/acp-25-11199-2025,https://doi.org/10.5194/acp-25-11199-2025, 2025
Short summary
McKenna Stanford, Ann Fridlind, Andrew Ackerman, Bastiaan van Diedenhoven, Qian Xiao, Jian Wang, Toshihisa Matsui, Daniel Hernandez-Deckers, and Paul Lawson

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2413', Anonymous Referee #1, 06 Sep 2024
  • RC2: 'Comment on egusphere-2024-2413', Anonymous Referee #2, 30 Sep 2024
  • AC1: 'Comment on egusphere-2024-2413', McKenna Stanford, 20 Jan 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2413', Anonymous Referee #1, 06 Sep 2024
  • RC2: 'Comment on egusphere-2024-2413', Anonymous Referee #2, 30 Sep 2024
  • AC1: 'Comment on egusphere-2024-2413', McKenna Stanford, 20 Jan 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by McKenna Stanford on behalf of the Authors (20 Jan 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (27 Jan 2025) by Raphaela Vogel
RR by Anonymous Referee #2 (20 Mar 2025)
RR by Anonymous Referee #3 (12 Jun 2025)
ED: Publish subject to minor revisions (review by editor) (13 Jun 2025) by Raphaela Vogel
AR by McKenna Stanford on behalf of the Authors (26 Jun 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (02 Jul 2025) by Raphaela Vogel
AR by McKenna Stanford on behalf of the Authors (15 Jul 2025)  Manuscript 

Journal article(s) based on this preprint

25 Sep 2025
Warm-phase microphysical evolution in large-eddy simulations of tropical cumulus congestus: evaluating drop size distribution evolution using polarimetry retrievals, in situ measurements, and a thermal-based framework
McKenna W. Stanford, Ann M. Fridlind, Andrew S. Ackerman, Bastiaan van Diedenhoven, Qian Xiao, Jian Wang, Toshihisa Matsui, Daniel Hernandez-Deckers, and Paul Lawson
Atmos. Chem. Phys., 25, 11199–11231, https://doi.org/10.5194/acp-25-11199-2025,https://doi.org/10.5194/acp-25-11199-2025, 2025
Short summary
McKenna Stanford, Ann Fridlind, Andrew Ackerman, Bastiaan van Diedenhoven, Qian Xiao, Jian Wang, Toshihisa Matsui, Daniel Hernandez-Deckers, and Paul Lawson
McKenna Stanford, Ann Fridlind, Andrew Ackerman, Bastiaan van Diedenhoven, Qian Xiao, Jian Wang, Toshihisa Matsui, Daniel Hernandez-Deckers, and Paul Lawson

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Short summary
The evolution of cloud droplets, from the point they are activated by atmospheric aerosol to the formation of precipitation, is an important process relevant to understanding cloud-climate feedbacks. This study demonstrates a benchmark framework for using novel airborne measurements and retrievals to constrain high-resolution simulations of moderately deep cumulus clouds and pathways for scaling results to large-scale models and space-based observational platforms.
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