Mesh¶

class
ESMF.api.mesh.
Mesh
(*args, **kwargs)¶ The Mesh class is a Python wrapper object for the ESMF Mesh. The individual values of all coordinate and mask arrays are referenced to those of the underlying Fortran ESMF object.
The ESMF library provides a class for representing unstructured grids called the Mesh. Fields can be created on a Mesh to hold data. Fields created on a Mesh can also be used as either the source or destination or both of a regrididng operation which allows data to be moved between unstructured grids. A Mesh is constructed of nodes and elements. A node, also known as a vertex or corner, is a part of a Mesh which represents a single point. Coordinate information is set in a node. An element, also known as a cell, is a part of a mesh which represents a small region of space. Elements are described in terms of a connected set of nodes which represent locations along their boundaries. Field data may be located on either the nodes or elements of a Mesh.
For more information about the ESMF Mesh class, please see the ESMF Mesh documentation.
An unstructured Mesh can be created in two different ways, as a Mesh in memory, or from a SCRIP formatted or CF compliant UGRID file. The arguments for each type of Mesh creation are outlined below.
Created inmemory:
 The inmemory Mesh can be created manually in 3 steps:
 create the Mesh (specifying
parametric_dim
andspatial_dim
),  add nodes,
 add elements.
 create the Mesh (specifying
REQUIRED:
Parameters:  parametric_dim (int) – the dimension of the topology of the Mesh (e.g. a Mesh composed of squares would have a parametric dimension of 2 and a Mesh composed of cubes would have a parametric dimension of 3).
 spatial_dim (int) – the number of coordinate dimensions needed to describe the locations of the nodes making up the Mesh. For a manifold the spatial dimension can be larger than the parametric dimension (e.g. the 2D surface of a sphere in 3D space), but it cannot be smaller.
OPTIONAL:
Parameters: coord_sys (CoordSys) – Coordinate system for the Mesh
. IfNone
, defaults toSPH_DEG
.Created from file:
Note that Meshes created from file do not use the
parametric_dim
andspatial_dim
parameters.REQUIRED:
Parameters:  filename (str) – the name of NetCDF file containing the Mesh.
 filetype (FileFormat) – the input
FileFormat
of the Mesh.
OPTIONAL:
Parameters:  convert_to_dual (bool) – a boolean value to specify if the
dual Mesh should be calculated. Defaults to False. This
argument is only supported with
SCRIP
.  add_user_area (bool) – a boolean value to specify if an area
property should be added to the mesh. This argument is only
supported for
SCRIP
orESMFMESH
. IfNone
, defaults to False.  meshname (str) – the name of the Mesh metadata variable in
a UGRID file. This argument is only supported with
UGRID
. IfNone
, defaults to the empty string.  mask_flag (MeshLoc) – an enumerated integer that, if
specified, tells whether a mask in a UGRID file should be
defined on the
UGRID
. IfNone
, defaults to no masking.  varname (str) – a variable name for the mask in a UGRID file
if mask_flag is specified. This argument is only supported
for
UGRID
. IfNone
, defaults to the empty string.

area
¶ Return type: A two element list of numpy arrays to hold values for the nodes and elements of the Mesh
.Returns: The Mesh
area represented as a numpy array of floats of the same number of entries as Mesh elements.

coords
¶ Return type: A two element list of numpy arrays to hold values for the nodes and elements of the Mesh
.Returns: The coordinates represented as a numpy array of floats with a value for each node and/or element of the Mesh Mesh
.

mask
¶ Return type: A two element list of numpy arrays to hold values for the nodes and elements of the Mesh
.Returns: The masked values on the nodes and elements of the Mesh
.

size
¶ Return type: A two element list of integers. Returns: The number of nodes and elements in the Mesh on the current processor.

size_owned
¶ Return type: A two element list of integers. Returns: The number of owned nodes and elements in the Mesh on the current processor.

add_elements
(element_count, element_ids, element_types, element_conn, element_mask=None, element_area=None, element_coords=None)¶ Add elements to a Mesh, this must be done after adding nodes.
REQUIRED:
Parameters:  element_count (int) – the number of elements to add to the Mesh.
 element_ids (ndarray) – a numpy array of of shape
(element_count, 1)
to specify the element ids.  element_types (ndarray) – a numpy array of
MeshElemType`s of shape ``(element_count, 1)`
to specify the element types.  element_conn (ndarray) – a numpy array of shape
sum(element_types[:], 1)
to specify the connectivity of the Mesh. The connectivity array is constructed by concatenating the tuples that correspond to the element_ids. The connectivity tuples are constructed by listing the node_ids of each element in COUNTERCLOCKWISE order.
OPTIONAL:
Parameters:  element_mask (ndarray) – a numpy array of shape
(element_count, 1)
containing integer values to specify masked elements. The specific values that are masked are specified in the Regrid() constructor.  element_area (ndarray) – a numpy array of shape
(element_count, 1)
to specify the areas of the elements.  element_coords (ndarray) – a numpy array of shape
(element_count, 1)
to specify the coordinates of the elements.

add_nodes
(node_count, node_ids, node_coords, node_owners)¶ Add nodes to a Mesh, this must be done before adding elements.
Parameters:  node_count (int) – the number of nodes to add to the Mesh.
 node_ids (ndarray) – a numpy array of shape (node_count, 1) to specify the node_ids.
 node_coords (ndarray) – a numpy array of shape (spatial_dim*node_count, 1) to specify the coordinates of the Mesh. The array should be constructed by concatenating the coordinate tuples into a numpy array that correspond to node_ids.
 node_owners (ndarray) – a numpy array of shape (node_count, 1) to specify the rank of the processor that owns each node.

free_memory
()¶ Free memory associated with the creation of a
Mesh
which is no longer needed for ongoing operations.

get_coords
(coord_dim, meshloc=<MeshLoc.NODE: 0>)¶ Return a numpy array of coordinates at a specified Mesh location (coordinates can only be returned for the Mesh :attr:`~ESMF.api.constants.MeshLoc.NODE`s at this time). The returned array is NOT a copy, it is directly aliased to the underlying memory allocated by ESMF.
REQUIRED:
Parameters: coord_dim (int) – the dimension number of the coordinates to return: e.g. [x, y, z] = (0, 1, 2)
, or[lat, lon] = (0, 1)
OPTIONAL:
Parameters: meshloc (MeshLoc) – the MeshLoc
of the coordinates. IfNone
, defaults toNODE
.Returns: A numpy array of coordinate values at the specified MeshLoc
.