Chapter 21
LIGHT SCATTERING MODELS AND
REFLECTANCE MEASUREMENTS IN REMOTE
SENSING OF SNOW
R. Kuittinen
Finish Geodetic Institute, Masala, Finland.
The snow pack characteristics are never stable because metamorphism
occurs all the time in different ways. This metamorphism can be destructive
or constructive, and both affect the crystals and grains of snow. The size and
shape of the grains and crystals as well as the structure and temperature of
the snow pack have great effects on the emittance and reflectance of
electromagnetic radiation from snow.
During the snow cover period three different phases can be distinguished
if the snow depth or water equivalent is the variable. These phase are
accumulation-, stable- and ablation phase. The weather circumstances and
snow characteristics in different phases can be described as follows.
1.
INTRODUCTION
201
M.M. Verstraete et al. (eds.), Observing Land from Space: Science, Customers and Technology, 201–208.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.
Accumulation phase.
Snow surface temperature is zero or below zero centigrade, grain size is
small, no diurnal variation of the snow surface temperature exist, albedo
is at its maximum, snow covers the terrain including trees, snow-less
patches do not exist and the thickness of the snow can vary from a thin
layer to its maximum. Solid precipitation occurs. Several accumulation
phases can exist during winter.
Stable phase.
Snow surface temperature is below zero, grain size increases, density
increases, diurnal variations of the snow surface temperature can exist,
1.
2.