EGU21-10326, updated on 04 Mar 2021
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Randomness in the amount of rain in LES with Lagrangian microphysics

Piotr Zmijewski, Piotr Dziekan, and Hanna Pawlowska
Piotr Zmijewski et al.
  • Institute of Geophysics, Faculty of Physics, University of Warsaw, Warsaw, Poland (

Lagrangian, particle-based models are an emerging method for detailed modeling of cloud microphysics. In these models, a relatively small number of "super-droplets" is used to represent all hydrometeors. Each super-droplet represents vast number of hydrometeors that have the same properties. The most popular method for solving collision-coalescence in these particle-based models is the all-or-nothing algorithm. In this algorithm, collision-coalescence of droplets within a spatial cell is modeled with a stochastic process. The number of trials is proportional to the number of super-droplets, which is significantly lower than the number of hydrometeors. Therefore the variance of the number of hydrometeors with a given size is higher in the super-droplet algorithm than it would be if every droplet was modeled separately. The increase of this variability depends on the number of super-droplets. We use the University of Warsaw Lagrangian Cloud Model (UWLCM) to analyse how the randomness in the collision-coalescence algorithm affects the amount of precipitation in large eddy simulations of warm clouds.

How to cite: Zmijewski, P., Dziekan, P., and Pawlowska, H.: Randomness in the amount of rain in LES with Lagrangian microphysics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10326,, 2021.

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