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Abstract
The strong increase in altimeter measurement errors near land surfaces is a limiting factor for coastal applications. We analyze the performance of the new Ka-band SARAL/AltiKa (SRL) mission in the northwestern Mediterranean Sea. SRL sea surface height (SSH) measurements are compared with those from the Jason-2 Ku-band satellite mission. The results show a significant increase in both quantity and quality of SSH data available near coastlines when using SRL data. Available edited data are 95.1% of SRL compared with 88.6% for Jason-2. Closer than 10 km to the coastline, available SRL data are still about 60% and only about 31% for Jason-2. Comparisons of the altimeter sea level variations are made with available coastal tide gauge data. The differences obtained between altimeter and tide gauge SLA time series are reduced for SRL (3.3 cm in average) compared with Jason-2 (4.2 cm in average), especially closer than 30 km to the land. It results in higher correlations (by 30%) obtained with SRL data. The coastal circulation derived from altimetry using SRL data shows an offshore meandering, which is more stable in time and with larger velocities close to the coast than that derived from Jason-2 observations.
Acknowledgements
Altimetry data were made available by AVISO/CNES, France. We wish to acknowledge the contribution of the French services that make the tide gauge data available: SONEL (http://www.sonel.org/) and REFMAR (http://refmar.shom.fr/). Finally, we thank Dr. Rosemary Morrow and the anonymous reviewers for fruitful advice that helped improve the manuscript.
Funding
This study was funded by the French Ministry of Research and the CNES through its TOSCA/OSTST program and by the CTOH/INSU. Support from these institutions is gratefully acknowledged.
