cemaneige_utils.py 文件源码

def extrapolate_precipitation(prec, altitudes, met_station_height):
    """Extrapolate precipitation to any given height.

    This function can be used to extrapolate precipitation data from the height
    of the meteorological measurement station to any given height. The routine
    is take from the Excel version, which was released by the Cemaneige's 
    authors [1].

    Args:
        prec: Numpy [t] array, which contains the precipitation input as 
            measured at the meteorological station.
        altitudes: Numpty [n] array of the median altitudes of each elevation
            layer.
        met_station_height: Scalar, which is the elevation above sea level of
            the meteorological station.

    Returns:
        layer_prec: Numpy [t,n] array, with the precipitation of each elevation
            layer n.

    [1] https://webgr.irstea.fr/en/modeles/modele-de-neige/
    """
    # precipitation gradient [1/m] defined in Cemaneige excel version
    beta_altitude = 0.0004

    # elevation threshold
    z_thresh = 4000

    # Number of elevation layer
    num_layers = len(altitudes)

    # Number of timesteps
    num_timesteps = prec.shape[0]

    # array for extrapolated precipitation of each elevation layer
    layer_prec = np.zeros((num_timesteps, num_layers), dtype=np.float64)

    # different extrapolation schemes depending on layer elevation
    for l in prange(num_layers):

        # layer median height smaller than threshold value
        if altitudes[l] <= z_thresh:
            layer_prec[:, l] = prec * np.exp((altitudes[l] - met_station_height)
                                             * beta_altitude)

        # layer median greater than threshold value
        else:

            # elevation of meteorological station smaller than threshold
            if met_station_height <= z_thresh:
                layer_prec[:, l] = prec * np.exp((z_thresh - met_station_height)
                                             * beta_altitude)

            # no extrapolation if station and layer median above threshold
            else:
                layer_prec[:, l] = prec

    return layer_prec