Abstract's details

Potential of the Noumea lagoon as a multi-mission cal/val site for past and future altimetry missions.

Clémence Chupin (LIENSs, UMR CNRS - La Rochelle Université, France)


Valérie Ballu (LIENSs, UMR CNRS - La Rochelle Université, France); Laurent Testut (LIENSs, UMR CNRS - La Rochelle Université, France); Yann-Treden Tranchant (LIENSs, UMR CNRS - La Rochelle Université, France)

Event: 2022 Ocean Surface Topography Science Team Meeting

Session: Regional and Global CAL/VAL for Assembling a Climate Data Record

Presentation type: Type Oral

At the interface between New-Caledonia and the Pacific Ocean, the Noumea Lagoon is an example of a dynamically complex coastal zone, that challenges the present and future altimetry mission. In this area, the SSH evolution is still an unresolved issue as sea level from altimetry and coastal tide gauge, and vertical land movements from GNSS, do not provide consistent information on long term trends (Aucan et al. 2017; Martínez-Asensio et al. 2019). This could be explained by multiple reasons, such as errors in the determination of GNSS Vertical Land Movements (VLM) due to mismodelled discontinuity (Ballu et al. 2019), a local elevation of the water body (setup) linked to waves and wind or the limitation of the altimetry data processing.

We addressed this question through the GEOCEAN-NC 2019 oceanographic campaign. During 3 weeks, we deployed various instruments in the lagoon, with a particular interest for the intersection zone of 3 altimetry tracks (1 Jason track and 2 Sentinel-3a tracks). To obtain in-situ sea level variations over the entire altimeter period at this particular location, we virtually transfered the Noumea tide gauge using observations from a GNSS buoy (2 days) and a bottom pressure sensor (1 year). In the same time, we analysed the 20Hz along-track data from Jason and Sentinel-3a GDRs according to the standards used on other historical cal/val sites. For that, we determined the optimal GDRs correction parameters, and integrated geoid gradients from the XGM2019 model, validated thanks to the CalNaGeo GNSS carpet measurements.

These two SSH time series (i.e. in-situ and altimetry) allow us to compute the altimeter biases over the entire Jason (1/2/3) and Sentinel-3a period. We show that the resulting altimeter biases are less than 10 cm for both Jason and Sentinel, with inter-mission biases consistent with other cal/val sites. With our 3 weeks field campaign, we have developed a relevant methodology to reanalyse 20 years of altimetry observations, and demonstrate the opportunities offer by the Noumea site to develop cal/val activities, for past, current and future missions. In this respect, several experiments are planned in 2023 to take advantage of the SWOT calibration phase 1-D repeat orbit.

Oral presentation show times:

Room Start Date End Date
Sala Grande Wed, Nov 02 2022,09:30 Wed, Nov 02 2022,09:45
Clémence Chupin
LIENSs, UMR CNRS - La Rochelle Université