Geology Reference
In-Depth Information
Albedo
0.65
0.75
0.85
Figure 8.27
Map of mean albedo derived from the ice thickness product of NASA's Radarsat Geophysical Processor
System. Cells that were initially square are shown distorted after 160 days of drifting and deformation (ending on
20 April, 1997). The inset shows a segment of Radarsat‐1 image acquired on 7 April, 1997. The solid dots mark the
location of Barrow, Alaska. Note the numerous cells of low albedo (dark tone) within the two ellipses that mark
locations at the ice edge [adapted from
Lindsay
, 2001].
occurring within the volume of snow‐covered ice. The
indirect inference between the two entities may add
sources of error but using radar data avoids the need for
introducing atmospheric corrections, cloud masking, and
angular integration of satellite observations.
Hanesiak
et al
. [2001] collected in situ data of albedo from FY ice
during the Collaborative‐Interdisciplinary Cryospheric
Experient (C‐ICE97) conducted in the early spring
of 1997 in the Willington Channel, Canadian central
Arctic. They also obtained a set of coincident radar back-
scatter coefficients from Radarsat‐1 and established the
following linear regression models to retrieve the albedo
(
α
) from a given backscatter coefficient
σ
0
(in dB) meas-
ured with polarization VV. Three sets of equations were
developed for the three stages of ice surface melt: (a)
winter and early melt, (b) melt onset, and (c) advanced
melt as defined in Figure 8.5. For the winter and early
melt phase,
where
θ
is SAR incidence angle. For the melt onset period
the following two equations apply to radar incidence
angle ranges around 20° and 30°, respectively:
2
0 141 095
.
.
0
0 002
.
0
(8.14)
2
0 853 031
.
.
0
0 002
.
0
(8.15)
And for the advanced melt season the linear regression
model is expressed by the following two equations, for
wind over melt ponds measured around 3.2 m/s and 5.3
m/s, respectively:
0 379 0 012
.
.
0
(8.16)
0 269 0 015
.
.
0
(8.17)
These equations are independent of the radar incidence
angle. None of the above equations (Eqs. 8.13-8.17) have
0
0 093 0 004
.
.
0 038
.
(8.13)
