2.2.2 Ice caps applications:

Results and comments

In the S-band, the radar waves penetrates deeper in the snow and ice than the Ku-band and it is less sensitive to the slope effect than the Ku-band. From this known physical properties, we're able to see differences on high altitude areas: over Central-East Antarctica, the S-band waves are less constrained by the slope effect and less attenuated by the snow grain, providing a bigger return echo than the Ku-band. This is clearly visible on the map below for the cycle 040 (Aug.-Sep.2005) where over East Antarctica, a long area with a north-south direction shows a positive difference between the two bands.
On the contrary, the Ku-band gives higher values over East Antarctica margins.
In southern winter (Envisat cycle 034, Jan.-Feb. 2005) and in southern summer (Envisat cycle 040, August-Sept. 2005), the figures below are quite similar (except for the resolution), we find essentially the same distribution for the backscatter difference.


Backcatter coefficient difference (in dB) between the S and the Ku-bands over Antarctica, from Envisat cycle 034 (left) and 040 (right). As explained above, we give an example with two different geographical resolutions: 1/3° on the left and 1° on the right.

The leading edge width in S-band tends to have smaller values than the Ku-band one toward the coastal areas over Greenland. On the contrary, the leading edge width in S-band has higher values on the plateau and its distribution seems to be lightly larger during winter (Envisat cycle 034 -below, left-).


Leading edge with difference (in m) between the S and the Ku-bands over Greenland, from Envisat cycle 034 (left) and 040 (right).

Further information:

Legrésy, B., Papa, F., Remy, F., Vinay, G., Van Den Bosch, M., Zanife, O-Z., Envisat radar altimeter measurements over continental surfaces and ice caps using the ICE-2 retracking algorithm, in Remote Sensing of Environment, Vol. 95 (2005), 150-163.