ICMW2021 Cumulus Congestus Case

ICMW 2021 case study
"Isolated cumulus congestus based on SCMS campaign: comparison between Eulerian bin and Lagrangian particle-based microphysics"


This is the website of ICMW 2021 cumulus congestus case, which is one of the four case studies for the 10th International Cloud Modeling Workshop (ICMW). Please contact the coordinators if you would like to participate.


Width of the droplet size distribution affects radiative properties of warm (ice-free) clouds and likely impacts formation of precipitation through collision/coalescence. One can argue that warm rain formation in bin microphysics models is affected by artificial spectral broadening in bin schemes (Morrison et al. 2018, Grabowski et al. 2019). Lagrangian particle-based schemes, on the other hand, are free from those problems, but may impact simulated cloud properties because of limited (and typically relatively small) number of super-droplets that can be used. This case aims at comparing cloud droplet distributions simulated by applying either spectral bin microphysics or Lagrangian particle-based microphysics. The modeling case is based on previous simulations of a case from the Small Cumulus Microphysics Study (SCMS) field campaign that took place in 1995 in Florida (USA) as described in Lasher-Trapp et al. (2005).

Case Description

Papers Based on this Case

  • Grabowski, W. W. (2020), Comparison of Eulerian bin and Lagrangian particle-based microphysics in simulations of nonprecipitating cumulus. J. Atmos. Sci., doi: https://doi.org/10.1175/JAS-D-20-0100.1.
  • Chandrakar, K. K., Grabowski, W. W., Morrison, H., & Bryan, G. H. (2021). Impact of entrainment-mixing and turbulent fluctuations on droplet size distributions in a cumulus cloud: An investigation using Lagrangian microphysics with a sub-grid-scale model, Journal of the Atmospheric Sciences (published online ahead of print 2021). Retrieved Aug 2, 2021, from https://journals.ametsoc.org/view/journals/atsc/aop/JAS-D-20-0281.1/JAS-D-20-0281.1.xml
  • Toshiki Matsushima, Seiya Nishizawa, Shin-ichiro Shima, and Wojciech Grabowski, “Intra-cloud Microphysical Variability Obtained from Large-eddy Simulations using the Super-droplet Method”, Preprint on Earth and Space Science Open Archive (2021) DOI: https://doi.org/10.1002/essoar.10508672.1.
  • Chandrakar, K. K., Morrison, H., Grabowski, W. W., & Bryan, G. H. (2022). Comparison of Lagrangian super-droplet and Eulerian double-moment spectral microphysics schemes in large-eddy simulations of an isolated cumulus-congestus cloud, J. Atmos. Sci., doi: https://doi.org/10.1175/JAS-D-21-0138.1.


Oct 2020: Gather the first results from the participants
Nov 2020: Pre-ICMW mini-workshop (virtual)
・ 16 Nov, 21-00 UTC: PI chamber case
・ 17 Nov, 21-00 UTC: Congestus case: https://s-shima-lab.sakura.ne.jp/events/pre-icmw_mini-ws
15 Feb 2021: Confirmation of new participants (registration deadline of ICMW)
Jun 2021: Gather all the results from all participants
26-30 Jul 2021: ICMW: https://iccp2020.tropmet.res.in/Cloud-Modeling-Workshop-2020
・27 Jul, 13-16 UTC: Congestus case: https://youtu.be/03WgWoDTHSI
02-06 Aug 2021: Present the summary at ICCP
Now preparing a manuscript

Example of Results

  • 3D
  • 2D
  • VR movie on youtube (created by Dr. Toshiki Matsushima). Best on VR headset. On your PC you can move it interactively by your mouse.

Current List of Models and Group Leaders (5 bin models and 6 particle-based models)

  • CM1 (Kamal Kant Chandrakar)
  • EULAG (Wojciech Grabowski)
  • PySDM (Sylwester Arabas)
  • SCALE-Bin (Yousuke Sato)
  • SCALE-SDM (Shin-ichiro Shima)
  • UWLCM (Piotr Dziekan)
  • WRF-HUCM (Kyoungock Choi)
  • WRF-UPNB (Lulin Xue)

Case coordinators

  • Shin-ichiro Shima (s_shima@sim.u-hyogo.ac.jp)
  • Wojciech W. Grabowski (grabow@ucar.edu)



  1. Grabowski, W. W., 2019: Separating physical impacts from natural variability using piggybacking technique. Adv. Geosci., 49, 105–111, 2019 https://doi.org/10.5194/adgeo-49-105-2019.
  2. Grabowski, W. W., Comparison of Eulerian bin and Lagrangian particle-based microphysics in simulations of nonprecipitating cumulus. J. Atmos. Sci., doi: https://doi.org/10.1175/JAS-D-20-0100.1.
  3. Lasher-Trapp, S.G., Cooper, W.A. and Blyth, A.M. (2005), Broadening of droplet size distributions from entrainment and mixing in a cumulus cloud. Q.J.R. Meteorol. Soc., 131: 195-220. https://doi.org/10.1256/qj.03.199.
  4. Morrison, H., M. Witte, G. H. Bryan, J. Y. Harrington, and Z. J. Lebo, 2018: Broadening of modeled cloud droplet spectra using bin microphysics in an Eulerian spatial domain. J. Atmos. Sci., 75, 4005–4030, https://doi.org/10.1175/JAS-D-18-0055.1.