Geology Reference
In-Depth Information
0
0
Freq. = 4.3 GHz
Freq. = 4.3 GHz
Mean vv
-10
-10
Mean vv
Mean hv
Mean hv
Smooth FY ice
-20
-20
White ice
-30
-30
-40
-40
ERS-1
SAR
≤ -16.4 dB
-8.8 ≤
ERS-1
SAR
≤ -27.8 dB
-23.3 ≤
-50
10
-50
10
20
30
40
50
60
20
30
Incidence angle (°)
40
50
60
Incidence angle (°)
0
0
Freq. = 4.3 GHz
Freq. = 4.3 GHz
Mean vv
Mean vv
-10
-10
Mean hv
Mean hv
-20
-20
Multiyear ice
-30
-30
Rough FY ice
-40
-40
ERS-1
SAR
≤ -15.5 dB
-12.1 ≤
ERS-1
SAR
≤ -15.1 dB
-11. 7 ≤
rough FY ice
My ice
-50
-50
10
10
20
30
40
50
60
20
30
40
50
60
Incidence angle (°)
Incidence angle (°)
Figure 8.3
Mean and standard deviation of backscatter coefficients from four ice types measured using a C‐band
ship‐borne scatterometer in the Weddell Sea, Antarctic. Curves are fitted exponentially and error bars indicate
the standard error of the data. Vertical lines delineate the incidence angle range of ERS SAR (20°-26°) and
the overlapping shaded pdf's show the probability distribution from SAR pixel samples. Vertical bars represent the
standard deviation of the measurements. It is negligibly small in the case of mean hv in the top panels. [
Drinkwater
,
1998, Figure 2, with permission from AGU].
that covers the entire range from < -20 dB for a quasi‐
steady ocean surface to -4.5 dB when the surface wind is
nearly 8 m/s
-1
. In general, the overlap of backscatter from
winter ice types has been confirmed in many later studies.
It is interesting also to note the wide range of backscatter
from a category labeled “unknown transition” at the ice
edge region. This is the most complicated region of ice
cover because it includes highly mobile young ice types at
sub-freezing temperatures (section 2.6.4). The ice surface
can vary significantly in terms of wetness, roughness,
salinity, porosity, and crystalline structure. Additionally, it
is more likely that the footprint of the satellite observation
can be heterogeneous and the ice surface is exposed to dif-
ferent forms of precipitation.
The radar signatures of ice types in the summer are
different than in winter due to surface melt and snow
metamorphosis.
Barber
[2005] presented a sketch show-
ing approximately the seasonal evolution of radar back-
scatter from FY and MY ice types over periods spanning
the annual sea ice cycle. Backscatter data were obtained
