https://www.mmm.ucar.edu/events/seminar/2025/dr-shin-ichiro-shima-133397
title: "20th anniversary of the super-droplet method"
speaker: Dr. Shin-ichiro Shima, University of Hyogo, Kobe, Japan
Mar. 20, 2025, 2:00 pm MDT (9 pm CET)
This seminar will be hybrid, you may attend in-person or watch the live
webcast: https://sundog.ucar.edu/public/page/MMM
Participants watching the live webcast may ask questions during the
seminar via Slido.
Abstract
(https://www.mmm.ucar.edu/sites/default/files/2025-03/Shin-ichiro%20Shima_Ma…):
The super-droplet method (SDM) is a Lagrangian particle-based numerical
algorithm designed to model cloud microphysics and its coupling with
cloud dynamics. It was 2005 when I joined Dr. Kanya Kusano’s group at
the Earth Simulator Center, JAMSTEC, Japan. With an eye on the future of
supercomputers, we worked on creating novel numerical algorithms for
multiscale-multiphysics phenomena. SDM was one of the significant
outcomes of our efforts. In Shima et al. (2009), we discussed the
general framework of SDM and key algorithms required for its numerical
implementation. Instead of applying Eulerian mixing ratios for various
predefined cloud condensate and precipitation categories (cloud water,
rain, cloud ice, snow, graupel, hail), SDM applies point particles,
referred to as super-droplets or super-particles, to represent
the enormous number of aerosol, cloud, and precipitation particles
present inside the simulated domain of a cloud model. The
super-particles are traced in physical space using the model-predicted
flow field, and they grow or shrink as they move with the flow. The
treatment of particle collision-coalescence was challenging, so we
constructed an efficient Monte Carlo algorithm to address it. In SDM,
the fundamental process rate equations are directly solved, allowing us
to seamlessly simulate various cloud related phenomena from the aerosol
scale to convective scale. SDM offers significant advantages over
Eulerian approaches typically used in cloud models, but it took a long
time for the idea to gain acceptance within the atmospheric science
community. Today, Lagrangian particle-based cloud models are being used
widely for various applications, and SDM has become synonymous with
them. In this talk, I will present an overview of recent advances and
applications of the Lagrangian particle-based cloud models. Those
include applications to warm-rain development studies, inclusion of
habit prediction and proper representation of various ice growth
mechanisms, and refinement of the numerical algorithms.
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