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\section{Tracer equations} |
\section{Tracer equations} |
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\label{sec:tracer_equations} |
\label{sect:tracer_equations} |
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The basic discretization used for the tracer equations is the second |
The basic discretization used for the tracer equations is the second |
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order piece-wise constant finite volume form of the forced |
order piece-wise constant finite volume form of the forced |
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described here. |
described here. |
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\subsection{Time-stepping of tracers: ABII} |
\subsection{Time-stepping of tracers: ABII} |
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\label{sec:tracer_equations_abII} |
\label{sect:tracer_equations_abII} |
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The default advection scheme is the centered second order method which |
The default advection scheme is the centered second order method which |
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requires a second order or quasi-second order time-stepping scheme to |
requires a second order or quasi-second order time-stepping scheme to |
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\section{Linear advection schemes} |
\section{Linear advection schemes} |
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\label{sect:tracer-advection} |
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<!-- CMIREDIR:linear_advection_schemes --> |
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\begin{figure} |
\begin{figure} |
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\resizebox{5.5in}{!}{\includegraphics{part2/advect-1d-lo.eps}} |
\resizebox{5.5in}{!}{\includegraphics{part2/advect-1d-lo.eps}} |
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The DST3 method described above must be used in a forward-in-time |
The DST3 method described above must be used in a forward-in-time |
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manner and is stable for $0 \le |c| \le 1$. Although the scheme |
manner and is stable for $0 \le |c| \le 1$. Although the scheme |
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appears to be forward-in-time, it is in fact second order in time and |
appears to be forward-in-time, it is in fact third order in time and |
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the accuracy increases with the Courant number! For low Courant |
the accuracy increases with the Courant number! For low Courant |
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number, DST3 produces very similar results (indistinguishable in |
number, DST3 produces very similar results (indistinguishable in |
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Fig.~\ref{fig:advect-1d-lo}) to the linear third order method but for |
Fig.~\ref{fig:advect-1d-lo}) to the linear third order method but for |