improver.wind_calculations.wind_components module

Module containing plugin to resolve wind components.

class improver.wind_calculations.wind_components.ResolveWindComponents

Bases: object

Plugin to resolve wind components along an input cube’s projection axes, given directions with respect to true North

static calc_true_north_offset(reference_cube)

Calculate the angles between grid North and true North, as a matrix of values on the grid of the input reference cube.

Parameters:reference_cube (iris.cube.Cube) – 2D cube on grid for which “north” is required. Provides both coordinate system (reference_cube.coord_system()) and template spatial grid on which the angle adjustments should be provided. Returns:Angle in radians by which wind direction wrt true North at each point must be rotated to be relative to grid North. Return type:angle_adjustment (numpy.ndarray)

process(wind_speed, wind_dir)

Convert wind speed and direction into u,v components along input cube projection axes.

Parameters:

• wind_speed (iris.cube.Cube) – Cube containing wind speed values
• wind_dir (iris.cube.Cube) – Cube containing wind direction values relative to true North

Returns:

tuple containing

ucube (iris.cube.Cube):

Cube containing wind speeds in the positive projection x-axis direction, with units and projection matching wind_speed cube.

vcube (iris.cube.Cube):

Cube containing wind speeds in the positive projection y-axis direction, with units and projection matching wind_speed cube.

Return type:

(tuple)

static resolve_wind_components(speed, angle, adj)

Perform trigonometric reprojection onto x and y axes

Parameters:

• speed (iris.cube.Cube) – Cube containing wind speed data
• angle (iris.cube.Cube) – Cube containing wind directions as angles from true North
• adj (numpy.ndarray) – 2D array of wind direction angle adjustments in radians, to convert zero reference from true North to grid North. Broadcast automatically if speed and angle cubes have extra dimensions.

Returns:

tuple containing

(iris.cube.Cube):

Cube containing wind vector component in the positive x-direction

(iris.cube.Cube):

Cube containing wind vector component in the positive y-direction

Return type:

(tuple)