def build_a_cdom(self, g, s, wave_const=400):
        """
        Builds the CDOM absorption function :: :math:`G \exp (-S(\lambda - 400))`

        :param g: function coefficient
        :param s: slope factor
        :param wave_const: wave constant default = 400 (nm)
        :returns null:
        """
        lg.info('building CDOM absorption')
        self.a_cdom = g * scipy.exp(-s * (self.wavelengths - wave_const))