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Semi-implicit semi-Lagrangian methods for numerical weather ...

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<strong>Semi</strong>-Implicit<br />

<strong>Semi</strong>-<br />

<strong>Lagrangian</strong><br />

Time-<br />

Stepping<br />

Methods and<br />

Regularized<br />

Fluid<br />

Equations in<br />

Numerical<br />

Weather<br />

Prediction<br />

Sebastian<br />

Reich<br />

Numerical<br />

Weather<br />

Prediction<br />

Basic Facts<br />

Unified Model<br />

Towards a<br />

New Dynamic<br />

Core<br />

Model System and<br />

Basic Ideas<br />

Results<br />

General<br />

Methodology<br />

Concluding<br />

Remarks<br />

The <strong>Semi</strong>-Implicit <strong>Semi</strong>-<strong>Lagrangian</strong> (SISL)<br />

Method<br />

The <strong>Semi</strong>-Implicit Part<br />

There is only one method that ‘comes to mind’. It is called<br />

the <strong>semi</strong>-<strong>implicit</strong> method in the meteorology community and<br />

the θ-method in <strong>numerical</strong> analysis:<br />

z n+1 − z n<br />

∆t<br />

= θf(z n+1 ) + (1 − θ)f(z n ).<br />

For θ = 1/2, it becomes the trapezoidal rule and, <strong>for</strong> θ = 1,<br />

it is the <strong>implicit</strong> Euler method.<br />

The <strong>Semi</strong>-<strong>Lagrangian</strong> Part<br />

Advection is treated in a <strong>semi</strong>-<strong>Lagrangian</strong> fashion.

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