A Model for the Complex Dielectric Constant of Supercooled Liquid Water at Microwave Frequencies

Measurements of the complex dielectric constant, or relative permittivity, spectrum of liquid water are modeled for frequencies up to 1 THz and temperatures up to 60 °C by a combination of two components: a Debye function, which characterizes the reorientation of the water molecules under the influence of an electric field, and a distributed-resonance function, which is associated with vibrations of intermolecular hydrogen bonds. This model provides a good representation of cloud measurements below 200 GHz at temperatures as low as -25 °C.