  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.
