Description of symbols
======================

This page explains some of the symbols used in the numerical documentation.


$\sum_\offProv{v2e}$
----------------------
This symbol is used to indicate summation over a set of points.
The offset provider ($\offProv{v2e}$) is read left to right, however the data itself "moves" from right to left (as in the
figure).
In this example the source points are the six (orange) edges adjacent to the
destination (blue) vertex.

.. image:: static/img/offsetProvider_v2e.png
   :alt: v2e
   :class: offset-provider-img

The corresponding code, computing the vorticity as rotor of velocity in this
example, is:

.. code-block:: python

   rot_vec = neighbor_sum(vec_e(V2E) * geofac_rot, axis=V2EDim)


$\Gradn_{\offProv{e2c}}$
------------------------
This symbol is used to indicate the difference (horizontal gradient) between two
points.
The offset provider ($\offProv{e2c}$) is read left to right, however the data itself "moves" from right to left (as in the
figure).
In this example source points are the two (orange) cells
adjacent to the destination (blue) edge.

.. image:: static/img/offsetProvider_e2c.png
   :alt: e2c
   :class: offset-provider-img

The corresponding code, computing the horizontal gradient in the normal
direction of the exner function in this example, is:

.. code-block:: python

   gradh_exner = inv_dual_edge_length * ( z_exner_ex_pr(E2C[1]) - z_exner_ex_pr(E2C[0]) )


$\nlev$
-------------
Number of (full) vertical levels.

$\nflatlev$
-------------
Number of flat vertical levels, located above the terrain-following levels.

$\nflatgradp$
-------------
Maximum height index at which an edge center lies
within two neighboring cells.