Sentinel-3 First look for Coastal Applications – Initial comparison with Cryosat-2 in the North Sea

Cryosat-2 offered the first ever possibility to perform coastal altimetric studies using SAR-Interferometry as well as SAR altimetry in preparation for the Sentinel-3 mission. With this technological leap forward it is now able to observe sea level in very small water bodies and also to provide coastal sea level very close to the shore. We perform an investigation into the retrieval of sea surface height in the North Sea and around Denmark and performing the first inter-comparison between SAR altimetry from Sentinel-3 and Cryosat-2. The availability of a radiometer on-board Sentinel-3 used for i.e. the wet troposphere corrections is also tested and compared with similar wet troposphere correction for Cryosat-2 based on a model (ESMWF)The use of the Cryosat-2 and Sentinel-3 is furthermore investigated for possible assimilation into sea level forecasting along the coasts of Denmark. This is a part of the EU sponsored project LOTUS in which the possibility of new Sentinel-3 downstream services are outlined . The advantage of the SAR data compared with conventional altimetry in the coastal zone, is the fact that the increased spatial resolution of Sentinel-3 and Cryosat-2 SAR provide valuable sea level observations within the narrow Straits around Denmark which are crucial to constrain the waterflow in and out of the Baltic Sea. These narrow straits were not well monitored by i.e. ENVISAT due to land contamination within the altimeter footprint.