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util

Functions:

  • rotate_from_lat_lon –

    This function applies a spherical rotation to a set of given latitude and

  • rotate_to_lat_lon –

    This function un-does a spherical rotation to a set of given latitude and

rotate_from_lat_lon 

rotate_from_lat_lon(
    lons, lats, lon_south_pole=18, lat_south_pole=-39.25
)

This function applies a spherical rotation to a set of given latitude and longitude coordinates, yielding coordinates in the rotated system.

Parameters:

  • lons

    ((list, ndarray)) –

    A one-dimensional list of longitude coordinates

  • lats

    ((list, ndarray)) –

    A one-dimensional list of latitude coordinates

  • lon_south_pole

    (float, default: 18 ) –

    The longitude of the rotated system's south pole

  • lat_south_pole

    (float, default: -39.25 ) –

    The latitude of the rotated system's south pole

Source code in reskit/weather/util.py 
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def rotate_from_lat_lon(lons, lats, lon_south_pole=18, lat_south_pole=-39.25):
    """This function applies a spherical rotation to a set of given latitude and
    longitude coordinates, yielding coordinates in the rotated system.

    Parameters
    ----------
    lons : list, numpy.ndarray
        A one-dimensional list of longitude coordinates

    lats : list, numpy.ndarray
        A one-dimensional list of latitude coordinates

    lon_south_pole : float
        The longitude of the rotated system's south pole

    lat_south_pole : float
        The latitude of the rotated system's south pole
    """
    lons = np.radians(lons)
    lats = np.radians(lats)

    # south pole is at 18 deg longitude
    theta = np.radians(90 + lat_south_pole)
    phi = np.radians(lon_south_pole)  # south pole is at -39.25 deg latitude

    x = np.cos(lons) * np.cos(lats)
    y = np.sin(lons) * np.cos(lats)
    z = np.sin(lats)

    x_new = np.cos(theta) * np.cos(phi) * x + np.cos(theta) * np.sin(phi) * y + np.sin(theta) * z
    y_new = -np.sin(phi) * x + np.cos(phi) * y
    z_new = -np.sin(theta) * np.cos(phi) * x - np.sin(theta) * np.sin(phi) * y + np.cos(theta) * z

    rlonCoords = np.degrees(np.arctan2(y_new, x_new))
    rlatCoords = np.degrees(np.arcsin(z_new))

    return rlonCoords, rlatCoords

rotate_to_lat_lon 

rotate_to_lat_lon(
    rlons, rlats, lon_south_pole=18, lat_south_pole=-39.25
)

This function un-does a spherical rotation to a set of given latitude and longitude coordinates (in the rotated), yielding coordinates in the regular longitude and latitude system.

Parameters:

  • rlons

    ((list, ndarray)) –

    A one-dimensional list of longitude coordinates in the rotated system

  • rlats

    ((list, ndarray)) –

    A one-dimensional list of latitude coordinates in the rotated system

  • lon_south_pole

    (float, default: 18 ) –

    The longitude of the rotated system's south pole

  • lat_south_pole

    (float, default: -39.25 ) –

    The latitude of the rotated system's south pole

Source code in reskit/weather/util.py 
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def rotate_to_lat_lon(rlons, rlats, lon_south_pole=18, lat_south_pole=-39.25):
    """This function un-does a spherical rotation to a set of given latitude and
    longitude coordinates (in the rotated), yielding coordinates in the regular
    longitude and latitude system.

    Parameters
    ----------
    rlons : list, numpy.ndarray
        A one-dimensional list of longitude coordinates in the rotated system

    rlats : list, numpy.ndarray
        A one-dimensional list of latitude coordinates in the rotated system

    lon_south_pole : float
        The longitude of the rotated system's south pole

    lat_south_pole : float
        The latitude of the rotated system's south pole
    """
    rlons = np.radians(rlons)
    rlats = np.radians(rlats)

    # south pole is at 18 deg longitude
    theta = -np.radians(90 + lat_south_pole)
    phi = -np.radians(lon_south_pole)  # south pole is at -39.25 deg latitude

    x = np.cos(rlons) * np.cos(rlats)
    y = np.sin(rlons) * np.cos(rlats)
    z = np.sin(rlats)

    x_new = np.cos(theta) * np.cos(phi) * x + np.sin(phi) * y + np.sin(theta) * np.cos(phi) * z
    y_new = -np.cos(theta) * np.sin(phi) * x + np.cos(phi) * y - np.sin(theta) * np.sin(phi) * z
    z_new = -np.sin(theta) * x + np.cos(theta) * z

    lonCoords = np.degrees(np.arctan2(y_new, x_new))
    latCoords = np.degrees(np.arcsin(z_new))

    return lonCoords, latCoords