class GenericFuncBaselevelHandler

Generic Function Baselevel Handler¶

GenericFuncBaselevelHandler modifies elevation for not-core nodes.

class GenericFuncBaselevelHandler(grid, modify_core_nodes=False, function=<function GenericFuncBaselevelHandler.<lambda>>, **kwargs)[source]

Bases: object

Control the elevation of all nodes that are not core nodes.

The GenericFuncBaselevelHandler controls the elevation of all nodes on the model grid with status != 0 (i.e., all not-core nodes). The elevation change is defined by a generic function of the x and y position across the grid and the model time, t. Thus a user is able to use this single BaselevelHandler object to make many different uplift patterns, including uplift patterns that change as a function of model time.

Through the parameter modify_core_nodes the user can determine if the core nodes should be moved in the direction (up or down) specified by the elevation change directive, or if the non-core nodes should be moved in the opposite direction. Negative values returned by the function indicate that the core nodes would be uplifted and the not-core nodes would be down-dropped.

The GenericFuncBaselevelHandler expects that topographic__elevation is an at-node model grid field. It will modify this field as well as the field bedrock__elevation, if it exists.

Note that GenericFuncBaselevelHandler increments time at the end of the run_one_step method.

__init__(grid, modify_core_nodes=False, function=<function GenericFuncBaselevelHandler.<lambda>>, **kwargs)[source]
Parameters
• grid (landlab model grid) –

• modify_core_nodes (boolean, optional) – Flag to indicate if the core nodes or the non-core nodes will be modified. Default is False, indicating that the boundary nodes will be modified.

• function (function, optional) – Function of model grid node x position, y position and model time that defines the rate of node elevation change. This function must be a function of three variables and return an array of size number of nodes. If a constant value is desired, used NotCoreNodeBaselevelHandler instead. The default function is: lambda grid, t: (0 * grid.x_of_node + 0 * grid.y_of_node + 0 * t)

Examples

Start by creating a landlab model grid and set its boundary conditions.

>>> from landlab import RasterModelGrid
>>> mg = RasterModelGrid((5, 5))
>>> mg.set_closed_boundaries_at_grid_edges(bottom_is_closed=True,
...                                        left_is_closed=True,
...                                        right_is_closed=True,
...                                        top_is_closed=True)
>>> mg.set_watershed_boundary_condition_outlet_id(
...     0, mg.at_node["topographic__elevation"], -9999.)
>>> print(z.reshape(mg.shape))
[[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]]


Now import the GenericFuncBaselevelHandler and instantiate.

>>> from terrainbento.boundary_handlers import (
...                                       GenericFuncBaselevelHandler)
>>> my_func = lambda grid, t:-(grid.x_of_node + grid.y_of_node + (0*t))
>>> bh = GenericFuncBaselevelHandler(mg,
...                                  modify_core_nodes = False,
...                                   function=my_func)
>>> bh.run_one_step(10.0)


We should expect that the boundary nodes (except for node 0) will all have lowered by 10*(x+y) in which x and y are the node x and y positions. The function we provided has no time dependence.

>>> print(z.reshape(mg.shape))
[[  0. -10. -20. -30. -40.]
[-10.   0.   0.   0. -50.]
[-20.   0.   0.   0. -60.]
[-30.   0.   0.   0. -70.]
[-40. -50. -60. -70. -80.]]


If we wanted instead for all of the non core nodes to change their elevation, we would set modify_core_nodes = True. Next we will do an example with this option, that also includes a bedrock elevation field.

>>> mg = RasterModelGrid((5, 5))
>>> b -= 10.
>>> mg.set_closed_boundaries_at_grid_edges(bottom_is_closed=True,
...                                        left_is_closed=True,
...                                        right_is_closed=True,
...                                        top_is_closed=True)
>>> mg.set_watershed_boundary_condition_outlet_id(
...     0, mg.at_node["topographic__elevation"], -9999.)
>>> my_func = lambda grid, t: -(grid.x_of_node + grid.y_of_node)
>>> bh = GenericFuncBaselevelHandler(mg,
...                                 modify_core_nodes = True,
...                                 function=my_func)
>>> bh.run_one_step(10.0)
>>> print(z.reshape(mg.shape))
[[  0.   0.   0.   0.   0.]
[  0.  20.  30.  40.   0.]
[  0.  30.  40.  50.   0.]
[  0.  40.  50.  60.   0.]
[  0.   0.   0.   0.   0.]]
>>> print(b.reshape(mg.shape))
[[-10. -10. -10. -10. -10.]
[-10.  10.  20.  30. -10.]
[-10.  20.  30.  40. -10.]
[-10.  30.  40.  50. -10.]
[-10. -10. -10. -10. -10.]]


There is no limit to how complex a function a user can provide. The function must only take the variables grid, and t and return an array that represents the desired rate of surface elevation change (dzdt) at each node.

If a user wanted to use this function to implement boundary conditions that involved modifying the grid, but not necessarily modifying the elevation of core or not-core nodes, then the function could modify the grid in the desired way and then return an array of zeros of size (n_nodes,).

run_one_step(step)[source]

Run GenericFuncBaselevelHandler forward and update elevations.

The run_one_step method provides a consistent interface to update the terrainbento boundary condition handlers.

In the run_one_step routine, the GenericFuncBaselevelHandler will either lower the closed or raise the non-closed nodes based on inputs specified at instantiation.

Note that GenericFuncBaselevelHandler increments time at the end of the run_one_step method.

Parameters

step (float) – Duration of model time to advance forward.