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Three-dimensional Lagrangian Tracer Modelling in Wadden Sea ...

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Contents<br />

List of Figures 1<br />

List of Tables 3<br />

1 Introduction 4<br />

2 Theory 6<br />

2.1 The physics and numerics of GETM . . . . . . . . . . . . . . 6<br />

2.1.1 Equations of motion . . . . . . . . . . . . . . . . . . 6<br />

2.1.2 Boundary conditions . . . . . . . . . . . . . . . . . . 8<br />

2.1.3 The turbulence model . . . . . . . . . . . . . . . . . 8<br />

2.1.4 Transport of tracers . . . . . . . . . . . . . . . . . . . 10<br />

2.1.5 Temporal discretisation: mode splitt<strong>in</strong>g . . . . . . . . 10<br />

2.1.6 Spatial discretisation . . . . . . . . . . . . . . . . . . 11<br />

2.2 The transport equation . . . . . . . . . . . . . . . . . . . . . 12<br />

2.2.1 The Fickian diffusion equation . . . . . . . . . . . . . 12<br />

2.2.2 The advection-diffusion equation . . . . . . . . . . . 16<br />

2.2.3 Turbulent diffusion . . . . . . . . . . . . . . . . . . . 17<br />

2.2.4 Eulerian vs. <strong>Lagrangian</strong> perspective . . . . . . . . . . 19<br />

2.3 <strong>Modell<strong>in</strong>g</strong> transport . . . . . . . . . . . . . . . . . . . . . . . 20<br />

2.4 <strong>Modell<strong>in</strong>g</strong> <strong>Lagrangian</strong> tracers . . . . . . . . . . . . . . . . . 22<br />

2.4.1 <strong>Modell<strong>in</strong>g</strong> advection . . . . . . . . . . . . . . . . . . 23<br />

2.4.1.1 Interpolation scheme . . . . . . . . . . . . . 23<br />

2.4.1.2 Analytical solution of the advection equation 24<br />

2.4.1.3 Interpolation between grid cells . . . . . . . 26<br />

2.4.1.4 Implementation . . . . . . . . . . . . . . . . 26<br />

2.4.2 <strong>Modell<strong>in</strong>g</strong> diffusion . . . . . . . . . . . . . . . . . . . 27<br />

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