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Australian Altimetry: From Precision Sea Level to Near-Real Time Delivery and Applications

Author:

Benoit Legresy - (CSIRO)

Co-Principle Investigator(s):

Christopher Watson (UNIVERSITY OF TASMANIA)

Abstract:

This proposal covers the continuation of works performed over the previous OSTST round and the contributions to the Sentinel-6 Validation Team, the SWOT Science team and Sentinel-3 Validation Team listed here:

  • Sentinel-6 VT by Watson and Legresy: Calibration and Validation of Sentinel-6 at the Bass Strait Satellite Altimetry Cal/Val Facility.
  • SWOT-ST by Watson and Legresy: An Australian contribution to SWOT validation from Bass Strait and surrounds.
  • SWOT-ST by Legresy et al.: Smaller Scales of the Southern Ocean Dynamics
  • Sentinel-3 VT by Watson and Legresy: Australian Cal/Val of Sentinel-3 Sea Surface Height

This proposal covers 3 thematic areas of investigation (covering specific topics 1, 2, 3, 4 and 8 of the call), each forming a separate work package summarized below:

Work Package 1: The Bass Strait Satellite Altimetry Cal/Val Facility. This facility has operated since the TOPEX/Poseidon launch and has run continuously since 2010 when it was incorporated into the Australian Integrated Marine Observing System (IMOS). Over the last 4 years the facility has evolved from monitoring just the Jason-series SSH at a historical comparison point to adding now continuous monitoring of Sentinel-3A and Sentinel-3B. Moored instrumentation operates year-round and periodic GNSS buoy deployments provide the connection to the absolute datum. The facility recently developed new equipment to be able to make an impact on the validation of higher resolution altimetry. This includes improved moored instrumentation, in particular the development of a Current, Waves, Pressure Inverted Echo Sounder (CWPIES) and a new version of the GNSS buoys capable of occupying sites of interest for a longer period (from just a few days to a goal of a few months at a time) and with an increasing number of buoys. Over this round of the OSTST we plan to continue the contribution of the Bass Strait site to the three Sentinel missions as well as expanding to support the SWOT mission. We will place a particular effort on the validation of higher resolution altimetry using improved in situ data – with a focus on mitigating systematic error contributions – collected along track. These along track segments will be monitored over a few months using Sentinel-SAR and in situ instrumentation. This work will culminate in dedicated deployments for the SWOT Fast Sampling Phase (FSP), before setting up continuous monitoring for the SWOT science mission.

Work Package 2: Global and Regional Mean Sea Level. We monitor global and regional sea level with an independent time series of mean sea level record production based on Level 2 (GDR) delayed mode (or NTC) products and various flavours of corrections and mapping. We also periodically perform global validation against the global tide gauge network to qualify the climate record (e.g. Watson et al., 2015). This sea level records feeds into sea level studies and regional and policy applications. This work is supported by the Australian National Environmental Science Program and the Australian Copernicus Hub and other national science funding opportunities.

Work Package 3: Southern Ocean Studies. As part of the planned SWOT validation activities in the Southern Ocean, we will develop a program of observation around a meander of the Antarctic circumpolar current south of Tasmania. We will then develop analysis and monitoring of the Southern Ocean dynamics by taking advantage of the much higher resolution provided by SWOT. Work has been on-going in preparation and includes analysis of Sentinel-3 SAR mode and in situ measurements accumulated over the last 2 years in the Southern Ocean. This work is supported by the Australian Antarctic Program Partnership over the next 4 years. This WP is essentially covered by the SWOT proposal with collaborators S. Rintoul from CSIRO, H. Phillips, M. Nikurashin and N. Bindoff from IMAS/University of Tasmania, K. Polzin from Woods Hole Oceanographic Institution, R. Watts from University of Rhode Island and R. Morrow from LEGOS.