Free Water is that portion of the pore water that is free to move between interconnected pores under the influence of gravity. The term Free Water also covers water in fissures, solution channels, and
other openings in soils or rocks. The temperature at which Free Water will change phase depends primarily on its dissolved-solids content, which determines the Freezing Point depression.
Fraction by weight of liquid water which is contained in the interstices between snow grains, but is not bound to individual grains and is free to move by capillarity or gravity.
The condition that exists when, over a widespread area, the surface temperature of the air remains below freezing (0C) for a sufficient time to constitute the characteristic feature of the weather. Th
is is a general term, and the time period necessary is usually considered to be two or more days; only the hardiest herbaceous crops survive. It differs from a dry freeze or black frost, for these terms are usually used to describe purely local freezing due to chilling of the surface air by rapid radiation from a restricted portion of the earth.