A software toolkit for generating ice and snow particle sharp data

Examensarbete för masterexamen

Please use this identifier to cite or link to this item: https://hdl.handle.net/20.500.12380/234473
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Type: Examensarbete för masterexamen
Master Thesis
Title: A software toolkit for generating ice and snow particle sharp data
Authors: Rathsman, Torbjörn
Abstract: Abstract Ice and snow particle shape data are important for understanding the scattering of microwave radiation from a cloud. This thesis presents a software toolkit that can be used to generate such data, for use with Discrete Dipole Approximation calculations. The toolkit has been used to implement a Gillespie-based algorithm with overlap rejection. This algorithm, when used with hexagonal columns, has reproduced some of the properties of real snowflakes, namely their fractal dimension, and their size distribution. The toolkit uses ice crystal prototypes to construct aggregates. Ice crystal prototypes can be modeled in 3D modelling software. This makes it is easy to construct exotic shapes, as opposed to a system based on different classes for different prototypes. In order to keep the possibility of arbitrary parameterisation, the ice crystal prototypes specifies transformation rules that are used if the ice crystal prototype should be deformed. Aggregates and ice crystal prototypes can be merged in different ways to form larger aggregates. To feed a DDA calculation program, the toolkit also provides a rasterisation system, which fills geometry with voxels by using a 6-directional floodfill algorithm. A large part of the thesis discusses various ways of measuring particles. This has lead to a unit neutral way of testing whether or not a model simulates reality. The idea is to compare an averaged spherical volume fill ratio, which according to measurements should follow a particular equation, derived within this thesis. Besides giving an overview of the toolkit, and presenting simulation results, this thesis also serves as a reference manual on how to use the toolkit.
Keywords: Data- och informationsvetenskap;Computer and Information Science
Issue Date: 2016
Publisher: Chalmers tekniska högskola / Institutionen för rymd- och geovetenskap
Chalmers University of Technology / Department of Earth and Space Sciences
URI: https://hdl.handle.net/20.500.12380/234473
Collection:Examensarbeten för masterexamen // Master Theses



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