Loss Factor of Supercooled Water at the Frequencies of 11...180 GHz

The loss factor of supercooled water at the frequencies 11...180 GHz has been measured. A measuring technique has been proposed, in which wetted nanoporous silicate materials, silica gels, with the mean diameter of the pores being 6-9 nm, were used to obtain deeply supercooled water. Results have been obtained for the loss factor of supercooled water, close to volume water for its properties, when cooled down to -45 {\deg}C. To ascertain the mechanism of pore water losses, measurements have been made in the range of temperatures 0...-90 {\deg}C. The results obtained have demonstrated the existence of significant excessive losses at the temperatures below -30 {\deg}C, compared to the results of computations based on the known models. To allow mathematical description of the increment loss factor, a new addend has been introduced as a sum of two Gaussian functions in the formula described in [T. Meissner, F. J. Wentz, IEEE Trans. Geosci. Remote Sens. 2004. vol. 42, p. 1836]. One of these functions has the extremum near -45 {\deg}C, and the second one has the extremum in the range of -60...-70 {\deg}C. Additional attenuation at -45 {\deg}C is supposed to be connected with the second critical point of water. Attenuation with the center in the range of temperatures -60...-70 {\deg}C is determined by the emergence of conductive films at the boundary between the hard matrix and ferroelectric ice 0. This modification is a transitional form to ice Ih or ice Ic and is formed at the temperature below -23 {\deg}C.