The water saturation of a natural snow cover varies, in general, from zero
to approximately 20% of the pore volume, whereby two essentially different
types of water geometry-pendular mode and funicular mode-can be observed. T
he pendular mode covers the low-saturation range (typically S less than or
equal to 7% for old coarse grained Alpine snow) and most of the water is pr
obably contained in veins; in the case that the snow has experienced freeze
-thaw cycles, the water component may be arranged in isolated menisci or pe
ndular rings around a contact zone between spheroidal ice grains. However,
the water rings or menisci are, thermodynamically, in a very critical-may b
e in an unstable-configuration. As water rings or menisci represent closed
electrically conducting loops, they may be responsible for an induced diama
gnetic behaviour of snow, especially in the microwave regime; and this offe
rs a way to measure the amount of water stored in this geometrical configur
ation. From a careful analysis of the measured dielectric and magnetic perm
eability in the microwave C- to K-bands of moderate wet coarse grained Alpi
ne snow results, water rings seem only to exist at saturations lower than a
pproximate to 8%. For saturations exceeding this critical value, water ring
s begin to merge forming clusters, whereby the number of ring-like geometri
es decreases in favor of larger but open-ended structures. (C) 1999 Elsevie
r Science B.V. All rights reserved.