CLEO - Clouds made Lagrangian, exascale and open-source#
Contact person
Description#
Cloud microphysics remains an integral and under-represented element of the climate system. Not only does this limit our understanding of clouds themselves, but also causes some of the largest uncertainties in climate modelling as a whole. CLEO is a SDM with collisional breakup for warm rain aiming to be computationally feasible in O(100km) LES.
The recently established Super-Droplet Model (SDM) is a promising alternative to conventional bulk and bin models for cloud microphysics. Briefly, SDM replaces traditional modelling of condensate distributions with Lagrangian particles, so called ‘Super-Droplets’, that act as representatives for the condensate populations of a cloud.
Besides its computational implementation, a defining feature of CLEO is its representation of collisional breakup. The microphysics in CLEO is similar to pre-established SDMs, except that the collision algorithm from Shima et al. 2009 has been extended to account not just for coalescence, but also for rebound and breakup. The novel algorithm still conserves the number of superdroplets, but introduces one new free parameter which determines the expected number of fragments produced by collisional breakup. In comparison with the original it considerably alters raindrop formation. We show how the evolution of the droplet spectrum is sensitive to the chosen number of fragments. Counterintuitively, we find that for certain choices of fragments’ number, rebound and collisional breakup act to increase the mean size of the final droplet distribution.
Model(s)#
CLEO :BSD 3-Clause
Programming language(s)#
C++ Python