JWG C.9 Climate Change Signals in High Resolution Surface Water Observations

Chair: Luciana Fenoglio (Germany)
Vice chair: Jessica Fayne (USA)
Affiliations: Commission 2, GGOS

Introduction

Altimetry observations cover the global oceans, cryosphere, sea-ice, ice-covered oceans and inland water bodies, providing invaluable geodetic and climatic information for studying the Earth and ocean dynamics and geophysical features. The contribution of surface water change to the global water cycle is monitored globally by satellite altimetric observations of high spatial and temporal resolution. Satellite radar altimeter measurements of sea surface heights have been continuously collected since the early 1990’s along the 10-day repeat ground tracks of TOPEX/Poseidon, Jason-1/2/3, and Sentinel-6 missions, along the 35-day repeat ground tracks of ERS-1/2, Envisat and SARAL, and the 27-day repeat ground tracks of Sentinel-3A/-3B. In high pulse repetition frequency radar altimeters, an innovative processing in SAR and SARIN modesreduces the coastal gap and provides water level at higher spatial resolution along-track. This last is increased to about 300 meters by the unfocused-SAR processing and to 0.5 meters, for an integration time of 2 sec, by the fully-focused SAR processing. Since December 2022, the Surface Water and Ocean Topography Mission (SWOT), provides globally observations of Water Surface Elevation (WSE) and water extent (WE) in rivers, lakes, reservoirs and right to the coast with an unprecedent spatial resolution. On ocean, SWOT closes for water height the observational gap between 100 km and 15 km wavelength, while observations of the surface roughness through the backscatter informs on the physical processes at and below the water surface.To detect climate related signals, we aim to investigate water surface change, river discharge and water storage change on land and surface water level at ice margins, coast and open ocean. For adaptation effort, we look at flood hazard event and to their mapping. We consider to study the impact of the different global terrestrial reference frames, e.g. ITRF2020, DTRF2020, JTRF2020, on both the altimeter measurement processing and the altimeter-derived geophysical parameters. It is agreed that a major limiting factor in the determination of global and regional sea level rise is the uncertainty of the Terrestrial Reference Frames in origin, scale and long-term stability. We propose to investigate the gain obtained by high-resolution (HR) altimetry 1-D and 2-D measurements, and to encourage innovative interdisciplinary researchand applications in climate change studies.

Objectives

• Develop an observational-based estimation of the components of the water ́watercycle.
• Extend the existing databases of water height, discharge, water storage, runoff, water extent, sea ice coverage, sea level
• Develop test cases for flood events to demonstrate the capability of the new space techniques for hazard mapping and early warning application
• Derive surface component of water cycle collaborating e.g. with space gravimetry, monitor groundwater and total water storage (TWS), sea level, discharge and other Essential Climate Variables (ECV).
• Test different global terrestrial reference frames and their impact on the altimeter-derived parameters, e.g. on sea level rise)
  

Program of Activities

• Support the IAG International Altimetry Service (IAS) Planning Group in generation of climate-related data products and services
• Support innovative interdisciplinary scientific research and applications for climate change detection
• collaborate with agencies and shakeholders
• Provide a forum for scientific exchange and training courses.
• Collaborate with existing ICCC working groups, e.g. JWG C.3, C.4, C.7
• Collaborate with study group 2.5 Satellite Altimetry of Commission 2 Gravity field (https://com2.iag-aig.org/sub-commission-25) e.g. with SG2.5.1.
• Participate to international science teams, e.g. Ocean Surface Topography (OSTST), SWOT Science Teams and Validation Teams (S3VT, S6VT)
• Collaborate with GGOS Standing Committee PLATO for the improvement of the Reference Frame with Space Techniques (https://ggos.org/about/org/bureau/bno/cwg/plato/).
  

Members

• Ole Andersen (Denmark)
• Jerome Benveniste (France)
• Christopher Buchhaupt (USA)
• Jan Martin Brockmann (Germany)
• Xiaoli Deng (Australia)
• Denise Dettmering (Germany)
• Michael Durand (USA)
• Joanna Fernandez (Portugal)
• Susanne Glaser (Germany)
• Cheinway Hwang (Taiwan)
• Per Knudsen (Denmark)
• Jürgen Kusche (Germany)
• Fernando Jamarillo (Sweden)
• Eric Leuliette (USA)
• Pascal Matte (Canada)
• Karina Nielsen (Denmark)
• Roelof Rietbroek (Netherlands)
• Louise Rousselet (France)
• Walter Smith (USA)
• C.K. Shum (USA)
• Stefano Vignudelli (Italy)
• Jida Wang (USA)