Improving collisional growth in Lagrangian cloud models: Development and verification of a new splitting algorithm

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Schwenkel, J.; Hoffmann, F.; Raasch, S.: Improving collisional growth in Lagrangian cloud models: Development and verification of a new splitting algorithm. In: Geoscientific Model Development 11 (2018), Nr. 9, S. 3929-3944. DOI:

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Sum total of downloads: 93

Lagrangian cloud models (LCMs) are increasingly used in the cloud physics community. They not only enable a very detailed representation of cloud microphysics but also lack numerical errors typical for most other models. However, insufficient statistics, caused by an inadequate number of Lagrangian particles to represent cloud microphysical processes, can limit the applicability and validity of this approach. This study presents the first use of a splitting and merging algorithm designed to improve the warm cloud precipitation process by deliberately increasing or decreasing the number of Lagrangian particles under appropriate conditions. This new approach and the details of how splitting is executed are evaluated in box and single-cloud simulations, as well as a shallow cumulus test case. The results indicate that splitting is essential for a proper representation of the precipitation process. Moreover, the details of the splitting method (i.e., identifying the appropriate conditions) become insignificant for larger model domains as long as a sufficiently large number of Lagrangian particles is produced by the algorithm. The accompanying merging algorithm is essential to constrict the number of Lagrangian particles in order to maintain the computational performance of the model. Overall, splitting and merging do not affect the life cycle and domain-averaged macroscopic properties of the simulated clouds. This new approach is a useful addition to all LCMs since it is able to significantly increase the number of Lagrangian particles in appropriate regions of the clouds, while maintaining a computationally feasible total number of Lagrangian particles in the entire model domain.
License of this version: CC BY 4.0 Unported
Document Type: article
Publishing status: publishedVersion
Issue Date: 2018
Appears in Collections:Fakultät für Mathematik und Physik

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pos. country downloads
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1 image of flag of Germany Germany 74 79.57%
2 image of flag of United States United States 15 16.13%
3 image of flag of Ukraine Ukraine 1 1.08%
4 image of flag of Russian Federation Russian Federation 1 1.08%
5 image of flag of China China 1 1.08%
6 image of flag of Brazil Brazil 1 1.08%

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