# NEMO periodicity
NEMO periodicity is defined as follow :
- closed boundary (in_perio=0)
- ghost cells (solid walls) are imposed at all model boundaries.
@image html perio0_20.png
@latexonly
\begin{center}
\includegraphics{perio0_20.png}
\end{center}
@endlatexonly
- cyclic east-west boundary (in_perio=1)
- first and last rows are closed, whilst the first column is set to the value of the last-but-one column and the last column to the value of the second one.
@image html perio1_20.png
@latexonly
\begin{center}
\includegraphics{perio1_20.png}
\end{center}
@endlatexonly
- symmetric boundary condition across the equator. (in_perio=2)
- last row, and first and last columns are closed.
@image html perio2_20.png
@latexonly
\begin{center}
\includegraphics{perio2_20.png}
\end{center}
@endlatexonly
- North fold boundary with a T -point pivot (in_perio=3)
- first row, and first and last columns are closed.
@image html perio3_20.png
@latexonly
\begin{center}
\includegraphics{perio3_20.png}
\end{center}
@endlatexonly
- North fold boundary with a T -point pivot and cyclic east-west boundary (in_perio=4)
- first row is closed. The first column is set to the value of the last-but-one column and the last column to the value of the second one.
@image html perio4_20.png
@latexonly
\begin{center}
\includegraphics{perio4_20.png}
\end{center}
@endlatexonly
- North fold boundary with a F -point pivot (in_perio=5)
- first row, and first and last columns are closed.
@image html perio5_20.png
@latexonly
\begin{center}
\includegraphics{perio5_20.png}
\end{center}
@endlatexonly
- North fold boundary with a F -point pivot and cyclic east-west boundary (in_perio=6)
- first row is closed. The first column is set to the value of the last-but-one column and the last column to the value of the second one.
@image html perio6_20.png
@image html perio5_20.png
@latexonly
\begin{center}
\includegraphics{perio6_20.png}
\end{center}
@endlatexonly
@sa For more information about NEMO periodicity, see _Model Boundary Condition_ chapter in [NEMO documentation](http://www.nemo-ocean.eu/About-NEMO/Reference-manuals))