Rényi entropy and finite Lyapunov exponents as metrics of transport and mixing in an idealised stratosphere

Examensarbete för masterexamen

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Type: Examensarbete för masterexamen
Master Thesis
Title: Rényi entropy and finite Lyapunov exponents as metrics of transport and mixing in an idealised stratosphere
Authors: Grahn, Jakob
Abstract: Most numerical metrics for diagnosing transport and mixing in fluid flows are based on calculating trajectories and thus knowing the velocity fields of the flows. Velocity fields are however difficult to measure globally on Earth. Tracer fields are on the other hand easier to measure and tracer based metrics could therefore prove to be valuable. A newly proposed metric based on the Rényi entropy of tracer values is examined. Although the metric has been used before, the exact theoretical connection to transport and mixing appears to be unclear to us. This motivates us to examine the metric under controlled circumstances. A simple model, defined by only a few parameters, is implemented and used as a test bench for comparing the metric with conventional trajectory based metrics. In particular, the finite time and the finite size Lyapunov exponents are considered for the comparison. We show that the Rényi entropy metric features the main transport barriers of the model and a positive correlation to the finite Lyapunov exponents is found.
Keywords: Grundläggande vetenskaper;Geovetenskap och miljövetenskap;Basic Sciences;Earth and Related Environmental Sciences
Issue Date: 2012
Publisher: Chalmers tekniska högskola / Institutionen för rymd- och geovetenskap
Chalmers University of Technology / Department of Earth and Space Sciences
URI: https://hdl.handle.net/20.500.12380/163109
Collection:Examensarbeten för masterexamen // Master Theses

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