improver.utilities.ancillary_creation module

class improver.utilities.ancillary_creation.OrographicAlphas(min_alpha=0.0, max_alpha=1.0, coefficient=1, power=1, invert_alphas=True)[source]

Bases: improver.BasePlugin

Class to generate alpha smoothing parameters for recursive filtering based on orography gradients.

__init__(min_alpha=0.0, max_alpha=1.0, coefficient=1, power=1, invert_alphas=True)[source]

Initialise class.

Parameters

  • min_alpha (float) – The minimum value of alpha that you want to go into the recursive filter.

  • max_alpha (float) – The maximum value of alpha that you want to go into the recursive filter

  • coefficient (float) – The coefficient for the alpha calculation

  • power (float) – What power you want for your alpha equation

_abc_cache = <_weakrefset.WeakSet object>
_abc_negative_cache = <_weakrefset.WeakSet object>
_abc_negative_cache_version = 213
_abc_registry = <_weakrefset.WeakSet object>
gradient_to_alpha(gradient_x, gradient_y)[source]

Generate alpha smoothing parameters from orography gradients in the x- and y- directions

Parameters

  • gradient_x (iris.cube.Cube) – A cube of the normalised gradient in the x direction

  • gradient_y (iris.cube.Cube) – A cube of the normalised gradient in the y direction

Returns

tuple containing:
alpha_x (iris.cube.Cube): A cube of orography-dependent

alphas calculated in the x direction.

alpha_y (iris.cube.Cube): A cube of orography-dependent

alphas calculated in the y direction.

Return type

(tuple)

process(cube)[source]

This creates the alpha cubes. It returns one for the x direction and one for the y direction. It uses the DifferenceBetweenAdjacentGridSquares plugin to calculate an average gradient across each grid square. These gradients are then used to calculate “alpha” smoothing arrays that are normalised between a user-specified max and min.

Parameters

cube (iris.cube.Cube) – A 2D cube of the orography for the grid we want to get alphas for.

Returns

containing:
alpha_x (iris.cube.Cube): A cube of orography-dependent

alphas calculated in the x direction.

alpha_y (iris.cube.Cube): A cube of orography-dependent

alphas calculated in the y direction.

Return type

(iris.cube.CubeList)

static scale_alphas(cubes, min_output=0, max_output=1)[source]

This scales a set of alphas from input cubes to range between the minimum and maximum alpha values.

Parameters

  • cubes (iris.cube.CubeList) – A list of alpha cubes that we need to take the cube_max and cube_min from.

  • min_output (float) – The minimum value we want our alpha to be

  • max_output (float) – The maximum value we want our alpha to be

Returns

A list of alpha cubes scaled to within the range specified.

Return type

iris.cube.CubeList

unnormalised_alphas(gradient_cube)[source]

This generates initial alpha values from gradients using a generalised power law, whose parameters are set at initialisation. Current defaults give an output alphas_cube equal to the input gradient_cube.

Parameters

gradient_cube (iris.cube.Cube) – A cube of the normalised gradient

Returns

The cube of initial unscaled alphas

Return type

iris.cube.Cube

static update_alphas_metadata(alphas_cube, cube_name)[source]

Update metadata in alphas cube. Remove any time coordinates and rename.

Parameters

  • alphas_cube (iris.cube.Cube) – A cube of alphas with “gradient” metadata

  • cube_name (str) – A name for the resultant cube

Returns

A cube of alphas with adjusted metadata

Return type

iris.cube.Cube

class improver.utilities.ancillary_creation.SaturatedVapourPressureTable(t_min=183.15, t_max=338.25, t_increment=0.1)[source]

Bases: improver.BasePlugin

Plugin to create a saturated vapour pressure lookup table.

__init__(t_min=183.15, t_max=338.25, t_increment=0.1)[source]

Create a table of saturated vapour pressures that can be interpolated through to obtain an SVP value for any temperature within the range t_min –> (t_max - t_increment).

The default min/max values create a table that provides SVP values covering the temperature range -90C to +65.1C. Note that the last bin is not used, so the SVP value corresponding to +65C is the highest that will be used.

Parameters

  • t_min (float) – The minimum temperature for the range.

  • t_max (float) – The maximum temperature for the range.

  • t_increment (float) – The temperature increment at which to create values for the saturated vapour pressure between t_min and t_max.

_abc_cache = <_weakrefset.WeakSet object>
_abc_negative_cache = <_weakrefset.WeakSet object>
_abc_negative_cache_version = 213
_abc_registry = <_weakrefset.WeakSet object>
process()[source]

Create a saturated vapour pressure lookup table by calling the Utilities.saturation_vapour_pressure_goff_gratch function in psychrometric_calculations.Utilities.

Returns

A cube of saturated vapour pressure values at temperature points defined by t_min, t_max, and t_increment (defined above).

Return type

iris.cube.Cube