def soil_thermal_conductivity(se_top):
    """
    Computes the soil thermal conductivity

    .. math ::
        k=0.15+18.5S_{e,top}

    Parameters
    ----------
    se_top : float
        effective saturation of the topsoil
        :math:`S_{e,top}`
        [-]

    Returns
    -------
    stc : float
        soil thermal conductivity
        :math:`k`
        [W m-1 K-1]

    Examples
    --------
    >>> import ETLook.radiation as rad
    >>> rad.soil_thermal_conductivity(se_top=0.4)
    0.8900000000000001
    """
    return 0.15 + 1.85 * se_top
