:py:mod:`opendrift.readers.reader_netCDF_CF_unstructured`
=========================================================

.. py:module:: opendrift.readers.reader_netCDF_CF_unstructured


Module Contents
---------------

Classes
~~~~~~~

.. autoapisummary::

   opendrift.readers.reader_netCDF_CF_unstructured.Reader




Attributes
~~~~~~~~~~

.. autoapisummary::

   opendrift.readers.reader_netCDF_CF_unstructured.logger


.. py:data:: logger

   

.. py:class:: Reader(filename=None, name=None, proj4=None)


   Bases: :py:obj:`opendrift.readers.basereader.BaseReader`, :py:obj:`opendrift.readers.basereader.UnstructuredReader`

   A reader for unstructured (irregularily gridded) `CF compliant
   <https://cfconventions.org/>`_ netCDF files.

   Args:
       :param filename: A single netCDF file, or a pattern of files. The
                        netCDF file can also be an URL to an OPeNDAP server.
       :type filename: string, requiered.

       :param name: Name of reader
       :type name: string, optional

       :param proj4: PROJ.4 string describing projection of data.
       :type proj4: string, optional

   .. seealso::

       py:mod:`opendrift.readers.basereader.unstructured`.

   Common constructor for all readers

   .. py:attribute:: variable_aliases

      

   .. py:attribute:: node_variables
      :value: ['salinity', 'temperature', 'sea_floor_depth_below_sea_level', 'sea_floor_depth_below_geoid',...

      

   .. py:attribute:: face_variables
      :value: ['x_sea_water_velocity', 'y_sea_water_velocity', 'upward_sea_water_velocity']

      

   .. py:attribute:: dataset

      

   .. py:attribute:: siglay

      

   .. py:attribute:: siglev

      

   .. py:attribute:: siglay_center

      

   .. py:attribute:: siglev_center

      

   .. py:attribute:: ocean_depth_nele

      

   .. py:attribute:: ocean_depth_node

      

   .. py:method:: plot_mesh()

      Plot the grid mesh. Does not automatically show the figure.


   .. py:method:: get_variables(requested_variables, time=None, x=None, y=None, z=None)

      FVCOM Grid:

      FVCOM uses 'triangular prisms' for gridding. Some variables are defined
      on the faces of the triangles, while others at the node.

      `x` and `y` holds the positions of the node, while `xc` and `yc` holds
      the positions on the centroids/faces. The centroids/faces are also
      known as 'zonal', or elements (presumably as in finite element).

      .. note::

          Currently this reader does not really interpolate. It looks up the
          closest point in time and space.

      Each element has a lookup-table of its surrounding elements, this list can be
      used when looking up elements for the interpolator of an arbitrary
      point on the grid. The same goes for the nodes.

      Let E be number of elements and N be number of nodes.

      Relevant lookup-tables:

      nbe:        [3 x E]  elements surround each element
      nbve:       [9 x N]  elements surrounding each node, minimum 3
      nbsn:       [11 x N] nodes surrounding each node

      Variables:

      Face:
      * u
      * v

      Node:
      * temperature
      * salinity



   .. py:method:: _vector_nearest_(X, xp)
      :staticmethod:

      Find nearest element in vector of vectors `X` for each `xp`.

      Args:

          X   NxM matrix of levels
          xp  M   vector of positions

      Returns:
          i   M   vector of indices [0..N] of closest element in
                  X[0..N, i] to xp[i]


   .. py:method:: __nearest_node_sigma__(var, nodes, z)

      Find nearest depth at node (sigma layer or sigma level depending on where the variable is defined).


   .. py:method:: __nearest_face_sigma__(var, el, z)

      Find nearest depth at element (sigma layer or sigma level depending on where the variable is defined).


   .. py:method:: z_from_sigma(sigma, depth, elevation=0)
      :staticmethod:

      Calculate z-depth from sigma constant.

      https://rdrr.io/github/edwardlavender/fvcom.tbx/src/R/depth_from_known.R

      Args:

          sigma       Sigma coefficient(s)
          depth       Depth below mean sea-surface
          elevation   Elevation of sea-surface (e.g. tidal)

      Returns: z, depth below sea-surface in meters.