Improving SAR Altimeter processing over the coastal zone and inland waters - the ESA HYDROCOASTAL project

David Cotton (Satellite Oceanographic Consultants Ltd, United Kingdom)

CoAuthors

Albert Garcia-Mondejar (isardSAT, Spain); Christine Gommenginger (National Oceanography Centre, United Kingdom); Ole Andersen (DTU Space, Denmark); Luciana Fenoglio-Marc (University of Bonn, Germany); Michele Scagliola (Aresys, Italy); Mathilde Cancet (NOVELTIS, France); Marcello Passaro (Technical University of Munich, Germany); Pierre Fabry (Along Track, France); Nicolas Bercher (AltiHydro Lab, France); Angelica Tarpanelli (CNR-IRPI, Italy); Stefano Vignudelli (CNR-IBF, Italy); Francesco De Biasio (CNR-ISP, Italy); Peter Bauer-Gottwein (DTU Environment, Denmark); Joana Fernandes (University of Porto, Portugal); Cornelis Slobbe (TU Delft, Netherlands); Jesus Gomez-Enri (University of Cadiz, Spain); Elena Zakharova (National University of Ireland, Maynooth, Ireland); Jérôme Benveniste (ESA-ESRIN, Italy); Marco Restano (SERCO,ESA, Italy)

Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)

Session: Science IV: Altimetry for Cryosphere and Hydrology

Presentation type: Type Forum

Introduction
The junction between the coastal zone and inland waters provides a challenge to researchers as it represents a boundary between different science domains (hydrology and oceanography), and different satellite measurement regimes. It is also a region of high variability in small spatial and temporal scales, pushing to the limit the ability of satellite data in terms of sampling and providing accurate measurements

HYDROCOASTAL is a two year project funded by ESA focussed on this problem, with the objective to maximise exploitation of SAR and SARin altimeter measurements in the coastal zone and inland waters, by evaluating and implementing new approaches to process SAR and SARin data from CryoSat-2, and SAR altimeter data from Sentinel-3A and Sentinel-3B. Optical data from Sentinel-2 MSI and Sentinel-3 OLCI instruments will also be used in generating River Discharge products.
New SAR and SARin processing algorithms for the coastal zone and inland waters will be developed and implemented and evaluated through an initial Test Data Set for selected regions. From the results of this evaluation a processing scheme will be implemented to generate global coastal zone and river discharge data sets.
A series of case studies will assess these products in terms of their scientific impacts.
All the produced data sets will be available on request to external researchers, and full descriptions of the processing algorithms will be provided

Objectives
The scientific objectives of HYDROCOASTAL are to enhance our understanding of interactions between the inland water and coastal zone, between the coastal zone and the open ocean, and the small scale processes that govern these interactions.

The technical objectives are to develop and evaluate new SAR and SARin altimetry processing techniques in support of the scientific objectives, including stack processing, and filtering, and retracking. Also an improved Wet Troposphere Correction will be developed and evaluated.

Project Outline
There are four tasks to the project
• Scientific Review and Requirements Consolidation: Review the current state of the art in SAR and SARin altimeter data processing as applied to the coastal zone and to inland waters
• Implementation and Validation: New processing algorithms with be implemented to generate a Test Data sets, which will be validated against models, in-situ data, and other satellite data sets. Selected algorithms will then be used to generate global coastal zone and river discharge data sets
• Impacts Assessment: The impact of these global products will be assess in a series of Case Studies
• Outreach and Roadmap: Outreach material will be prepared and distributed to engage with the wider scientific community and provide recommendations for development of future missions and future research.

Project Outputs
Outputs and products that will be publicly available include
• Detailed technical descriptions of the algorithms and processing schemes applied.
• Initial validation coastal zone and inland water Test Data Sets for selected regions,
• Improved Wet and Dry Troposphere Corrections for the coastal zone and inland waters
• A final global coastal zone product, and a river discharge product for large and medium sized rivers.
• An impacts assessment report on the applications and benefits of these global products
• A scientific roadmap with recommendations for further development of processing algorithms, for further SAR and SARin altimeter missions, and priorities for further scientific research in the coastal zone and inland waters.

Project Impact
The potential benefits of global data sets will be investigated through a series of impact assessment case studies in the second year of the project.

Case studies will consider different estuaries and coastal regions including the Bristol Channel in the UK, the German Bight and South-Western Baltic Sea, the Venice Lagoon, the Thailand Coast, and the Ebro River and Delta. They each have specific issues, common across the locations are flooding and erosion, sedimentation, the importance of accurate high resolution local modelling, the vulnerability of coastal habitats, the connection between river discharge and coastal sea levels

Inland Water Case Studies will consider selected river systems in China to investigate the potential to develop operational hydrological forecasting, lakes and rivers in Siberia and Ireland to investigate the impacts of lake size and riverbank configuration on the accuracy of water level retrievals, to quantify the fresh water inflow to the Wadden Sea, and to develop a global water level climatology.

Presentation
The presentation will provide an overview to the project, present the different SAR altimeter re-tracking algorithms that are being evaluated in the first phase of the project, and outline the content of the initial test data set that will be used for this evaluation.
 
David Cotton
Satellite Oceanographic Consultants Ltd
United Kingdom
d.cotton@satoc.eu