Sentinel-3 Delay Doppler Altimeter: a New Insight on High Resolution Ocean Dynamics

Sylvie Labroue (CLS, France)

CoAuthors

Matthias Raynal (CLS, France); Thomas Moreau (CLS, France); Jean Christophe Poisson (CLS, France); Laiba Amarouche (CLS, France); Gérald Dibarboure (CLS, France); François Boy (CNES, France); Nicolas Picot (CNES, France)

Event: 2015 Ocean Surface Topography Science Team Meeting

Session: Quantifying Errors and Uncertainties in Altimetry data

Presentation type: Type Poster

Although conventional radar altimetry products (Jason1, Jason2, LRM Cryosat-2, etc) have a spatial resolution between 5 and 10 km (due to the size of the radar footprint), the observation of ocean scales in the along track direction smaller than 100 km is limited by the existence of a “spectral bump”, i.e. a geographically coherent error between 10 and 20 km, observed on all conventional altimeters.
Dibarboure et al (2014) have largely discussed the bump artefact which appears to be a mixed effect between the Brown model used for retracking the data (which has been designed for a homogeneous scene and is not fully relevant during backscattering events) and the criteria for selecting the 20 Hz valid data. They showed that dedicated processing could better discard outliers and reduce the energy in the mean PSD of the sea level. More recently, dedicated editing procedure based on the mispointing angle on AltiKa (Poisson et al OSTST 2014) has also enhanced the description of the corrupted data. In parallel, other groups are also working on retracking as Amarouche and Sandwell, also showing some significant improvement.
Another important issue for understanding the oceanic turbulence at short scales is the use of the new delay Doppler technique that should yield measurement less altered by the heterogeneities issue since the thin stripe-shaped synthetic footprint of SARM is reduced to 300 m in the along track direction. Preliminary results have shown that the SARM data derived from Cryosat-2 do not show the spectral bump.
As the delay Doppler processing have become more mature in the last couple of years, the content of the shortest spatial scales is further investigated here by analyzing several oceanic regime acquired in SAR mode with Cryosat-2 mission and comparing the results with other LRM processing (AltiKa, Jason-2 and Cryosat-2).
This work allows understanding the outcomes of the SARM processing that we could expect from Sentinel-3 mission. Furthermore, in the frame of the future altimetry missions (SAR for Cryosat -2 and Sentinel-3 missions and interferometry for the SWOT mission), it becomes crucial to investigate again and to better understand the signals obtained at small scales by conventional altimeter missions.

 

Poster show times:

RoomStart DateEnd Date
Grand Ballroom Foyer Thu, Oct 22 2015,11:00 Thu, Oct 22 2015,18:00
Sylvie Labroue
CLS
France
sylvie.labroue@cls.fr