earthkit.geo.rotate.unrotate_vector

earthkit.geo.rotate.unrotate_vector(lat, lon, vector_x, vector_y, south_pole_lat, south_pole_lon, south_pole_rotation_angle=0, lat_unrotated=None, lon_unrotated=None)

Rotate vectors on a rotated grid back into eastward and northward components.

Parameters:

• lat (ndarray) – Latitude coordinates of the rotated points (degrees).

• lon (ndarray) – Longitude coordinates of the rotated points (degrees).

• vector_x (ndarray) – x vector component in the rotated coordinate system at the rotated points.

• vector_y (ndarray) – y vector component in the rotated coordinate system at the rotated points.

• south_pole_lat (float) – Latitude of the south pole defining the rotation (degrees).

• south_pole_lon (float) – Longitude of the south pole defining the rotation (degrees).

• south_pole_rotation_angle (float, optional) – Rotation angle around the south pole (degrees). Currently not supported.

• lat_unrotated (ndarray, optional) – Latitude coordinates of the points before rotation (degrees).

• lon_unrotated (ndarray, optional) – Longitude coordinates of the points before rotation (degrees).

Returns:

• ndarray – x component of the vector rotated back to eastward and northward components.

• ndarray – y component of the vector rotated back to eastward and northward components.

Use this method when a grid is rotated spherically and the vector components are locally rotated at each target grid point into the new local (rotated) coordinate system. unrotate_vector() performs the inverse operation, and rotates back the vectors to their original directions at each point. The vector is returned at the same locations (lat, lon) and its magnitude is preserved.