Abstract's details

Performance analysis of the SWIM ground-segment solution for retracking nadir echos

Annabelle Ollivier (cls, France)


Fanny Piras (cls, France); Maeva Dalila (cls, France); Gautier Dekeyne (cls, France); Cedric Tourain (cnes, France); Jean Michel Lachiver (cnes, France); Alice Dalphinet (MeteoFrance, France)

Event: 2019 Ocean Surface Topography Science Team Meeting

Session: CFOSAT

Presentation type: Type Oral

Contribution: PDF file


The new satellite mission CFOSAT has been launched on October 29th, 2018. It provides, for the first time, colocated and global observations of the surface ocean wind and wave. Wind vectors and ocean wave spectral parameters will be derived from a combination of two Ku-Band radar instruments: a 6 beams incidence diffusiometer (nadir, 2°, 4°, 6°, 8° and 10°) measuring sigma0 profiles and wave spectra (SWIM) and wind scatterometer mode (SCAT).
At 0°, SWIM is a nadir altimeter acquiring at a 5Hz rate. And for the first time in a reference ground segment, the retracking used to extract ocean parameters is the so-called Adaptive retracker uses an adaptive model which takes into account the roughness of the surface. This solution, deriving four geophysical parameters: Epoch, Significant Wave Height, Sigma0 and Mean Square Slope, was chosen for its particularly good performances at deriving precise and high rate Significant Wave Height.
The aim of this presentation is to present the global performances of the ground segment retracking algorithm for the SWIM altimeter. During this talk, after an introduction of the retracking itself, global performances of the geophysical parameters will be presented and assessed via several diagnoses, including (but not limited to) comparisons with models and other altimetric missions such as Jason-3, Altika and Sentinel-3.
This presentation will also focus on the parameter “Mean Square Slope” related to the surface and derived by this algorithm. This new parameter will not only ensure a continuity of estimations between typical Brownian waveforms and peaky waveforms, (acquired over Arctic leads or bloom events for instance), but will also give useful information about the roughness of the surface.
Finally, we will illustrate and quantify the capacity of these data to improve the MeteoFrance models assimilating altimetric data.

Oral presentation show times:

Room Start Date End Date
The Monroe Hub Thu, Oct 24 2019,11:20 Thu, Oct 24 2019,11:40
Annabelle Ollivier