Unidata / MetPy

    #

    # Depth is in pressure

    if depth.dimensionality == {'[length]': -1.0, '[mass]': 1.0, '[time]': -2.0}:

        top_pressure = bottom_pressure - depth

        if heights is not None:

            top_height = log_interp(top_pressure, p, heights)

        else:

            top_height = pressure_to_height_std(top_pressure)

    # Depth is in height

    elif depth.dimensionality == {'[length]': 1.0}:

        top_height = bottom_height + depth

        if heights is not None:

            top_pressure = np.interp(np.array([top_height.m]), heights, p)[0] * p.units

        else:

            top_pressure = height_to_pressure_std(top_height)

    # Depth is in invalid units

    else:

        raise ValueError('Depth must be in units of length or pressure.')

    # Handle top or bottom values that are invalid

    if bottom_pressure > p[0]:

    # If the bottom pressure is specified

    else:

        # in pressure units, assign it

        if bottom.dimensionality == {'[length]': -1.0, '[mass]': 1.0, '[time]': -2.0}:

            bottom_pressure = bottom

            if heights is not None:

                bottom_height = log_interp(bottom_pressure, p, heights)

            else:

                bottom_height = pressure_to_height_std(bottom_pressure)

        # in height units

        elif bottom.dimensionality == {'[length]': 1.0}:

            bottom_height = bottom

            if heights is not None:

                bottom_pressure = np.interp(np.array([bottom_height.m]), heights,

                                            p)[0] * p.units

            else:

                bottom_pressure = height_to_pressure_std(bottom_height)

    #

    # Top of layer calculations