Science Service System

Summary of Proposal OCE2395

TitleCross-comparison of altimetric high resolution missions with TerraSAR-X Wide ScanSAR : understanding sea ice structures, river behaviour and small scale ocean signals
Investigator DURAND, Philippe - CNES, DCY/SI/AR
Team Members
Engineer BOY, Francois - CNES, DCT/SI/AR
Engineer GUILLOT, Amandine - CNES, DCT/SI/AR
Engineer POURTHIE, Nadine - CNES, DCT/SI/AR
SummarySea ice ( frozen sea water ) covers the Arctic Ocean more or less permanently above 75 N. Sea ice does not directly affect the mean sea level if it begins to melt. However, because of its high albedo , ice directly affects the overall energy balance of the Earth. The thickness of the sea ice in the Arctic also plays a major role in the polar climate because it tends to moderate the heat exchange by exposure of the ocean by the cold polar atmosphere . In addition, when ice forms, salinity and therefore the density of the upper layers of the ocean increases which causes a dip of surface water, which acts as a pump and leads the deep and cold waters of the polar regions to the equator. Observations show that the average extent of Arctic sea ice decreases by about 3 % per decade while the extended Antarctica is relatively stable or increasing. Regional patterns of sea ice has expanded greatly over the last decade .However, given the impact of sea ice on the climate, it is essential to increase the data acquisitions of sea ice in order to improve the models and the resulting climate studies. Oceanology/hydrology : The conventional altimetry has been designed and developed since the early 1970s to measure the dynamic height of the ocean and its variability on a global scale. Indeed, it has become possible today, using measurements from Jason, Envisat and more recently SARAL/Altika satellites, to make maps of the topography of the ocean surface, and especially to monitor and understand the overall functioning of the oceans and their involvement in the climate dynamics. A new concept altimeter called Doppler altimeter, was proposed by Raney in 1998. This system uses the Doppler information along the track to improve the on-ground spatial resolution (300 m against 20km for conventionnal altimetry) . This new concept, already developped and embarked on CryoSat-2 mission, should offer the possibility to oberserve very small scale signals never measured by the conventionnal missions. Moreover, this high resolution mode should give the opportunity to better monitor in-land water and rivers. Today, Cryosat-2 data in doppler mode are processed by CNES dedicated processor over mediterranean sea and amazon.It has already been demonstrated that it's now possible to look at small roughness variability of the sea surface. Over Amazon, the results confirm the capability of this new mode to precisely characterize the river. The objective of this proposal is to cross-compare those primising results with TerraSAR-X simultaneous observations.

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DLR 2004-2016