What is the thermal infrared emissivity of ice?
- Warren (1982) reports that the "infrared emissivity of snow is quite insensitive to snowpack parameters. For many purposes one can simply assume a snow emissivity of about 99%, as was measured by Griggs ".
- Hobbs (1974, p. 223) devotes part of one page to the subject. "Since the
absorptivity of ice is large for wave numbers below 10 000 cm-1, and the
reflectivity is small, the emissivity of ice should be close to unity in
the infrared region"
- Rao, et al. (1990, p. 30-32) provide a few, primarily qaulitative
comments on snow and ice emissivity. "...emisivity appears to decrease as
the frequency increases, unlike most other natural surfaces. As sea ice
ages, bubbles, racks and other metamophosing processes give an unsmooth
texture and create scattering centers. Emissivities of heterogeneous
substances (multiyear sea ice and dry snow) which contain scatterers have
been computed by Poe et al. (1972), Hoffer and Matzler, (1980), and Chang
et al. (1976). Since the depth of MW penetration increases with decreasing
frequency, multspectral measurements have been used for determining the
subsurface characteristics of sea ice (Hollinger et al., 1984; Cavalieri et
al., 1983). The analysis becomes more complex when stratification of
different surfaces occurs, e.g., snow over ice, or ice over water
(England, 1975). Identification of stratified ice and snow layers also may
be possible from polarization measurements."
Rao et al. present a graph which shows 'lake and new sea ice' to have emissivities of approximately 0.85 between 10 and 37 GHz, increasing slightly with frequency. (No citation?)
AVHRR band 4 density slice image
AVHRR band 4 6 class
AVHRR band 4 red temp. color table
AVHRR band 4 stern color table
AVHRR band 4 histogram equalized
AVHRR band 4 temperature profile image
AVHRR band 4 temperature profile plot
AVHRR band 4 another density slice