Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
doi:10.5194/gmd-2016-271
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Model evaluation paper
28 Nov 2016
Review status
A revision of this discussion paper was accepted for the journal Geoscientific Model Development (GMD) and is expected to appear here in due course.
Collection/aggregation algorithms in Lagrangian cloud microphysical models: Rigorous evaluation in box model simulations
Simon Unterstrasser1, Fabian Hoffmann2, and Marion Lerch1 1Deutsches Zentrum für Luft- und Raumfahrt (DLR) – Institut für Physik der Atmosphäre, Oberpfaffenhofen, 82234 Wessling, Germany
2Leibniz Universität Hannover – Institute of Meteorology and Climatology, 30419 Hannover, Germany
Abstract. Recently, several Lagrangian microphysical models have been developed which use a large number of (computational) particles to represent a cloud. In particular, the collision process leading to coalescence of cloud droplets or aggregation of ice crystals is implemented differently in the various models. Three existing implementations are reviewed and extended, and their performance is evaluated by a comparison with well established analytical and bin model solutions. In this first step of rigorous evaluation, box model simulations with collection/aggregation being the only process considered have been performed for the three well-known kernels of Golovin, Long and Hall.

Besides numerical parameters like the time step and the number of simulation particles (SIPs) used, the details of how the initial SIP ensemble is created from a prescribed analytically defined size distribution is crucial for the performance of the algorithms. Using a constant weight technique as done in previous studies greatly underestimates the quality of the algorithms. Using better initialisation techniques considerably reduces the number of required SIPs to obtain realistic results. From the box model results recommendations for the collection/aggregation implementation in higher dimensional model setups are derived. Suitable algorithms are equally relevant to treating the warm-rain process and aggregation in cirrus.


Citation: Unterstrasser, S., Hoffmann, F., and Lerch, M.: Collection/aggregation algorithms in Lagrangian cloud microphysical models: Rigorous evaluation in box model simulations, Geosci. Model Dev. Discuss., doi:10.5194/gmd-2016-271, in review, 2016.
Simon Unterstrasser et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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RC1: 'Referee Comment', Anonymous Referee #1, 11 Jan 2017 Printer-friendly Version 
AC1: 'Reply to Reviewer 1', Simon Unterstrasser, 03 Mar 2017 Printer-friendly Version Supplement 
 
RC2: 'Referee comment', Anna Jaruga, 13 Jan 2017 Printer-friendly Version 
AC2: 'Reply to Anna Jaruga', Simon Unterstrasser, 03 Mar 2017 Printer-friendly Version Supplement 
Simon Unterstrasser et al.
Simon Unterstrasser et al.

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