Abstract's details

Improving the continuity of the Jason SSB time-series

Ngan Tran (CLS, France)

CoAuthors

Gérald Dibarboure (CNES, France); Nicolas Picot (CNES, France)

Event: 2018 Ocean Surface Topography Science Team Meeting

Session: Instrument Processing: Propagation, Wind Speed and Sea State Bias

Presentation type: Type Poster

Contribution: PDF file

Abstract:

Most of the operational versions of the Sea State Bias (SSB) correction are computed empirically with the nonparametric estimation technique based on kernel smoothing described in Gaspar et al [2002]. These solutions are derived from 10-day SSH differences (i.e. collinear analysis of repeat cycles of data or from crossover differences). Since only SSB differences are observed, the SSB solution can only be determined to within a constant when solving the equation system. This leads to potentially observe some solution shift related to the imposed constraint to have a SSB value equal to 0 for a flat surface between two versions of the SSB correction. This (constant) shift can reach a few centimeters when the SSB correction version is updated to consider SSH standard changes due to large uncertainty in data-poor region close to (SWH=0, WS=0) to correctly constrain the estimation of SSB(0, 0).
This causes annoying disturbances every time that SSB solutions are updated for the monitoring of multi-mission altimeter biases at in-situ Cal/Val sites or for the intermission bias alignment needed to tie up the different global mean sea level time-series together.
This presentation will seek to propose changes in SSB model development to tackle/reduce the SSB constant shift issue that exists between different correction versions for a same altimetric mission or for different missions all operating at a same radar frequency. The work will focus on the Jason altimeters time-series, both Ku- and C-band data, to better connect the past and current missions.

 

Poster show times:

Room Start Date End Date
Foyer, Salao Nobre & tent Thu, Sep 27 2018,18:00 Thu, Sep 27 2018,20:00
Foyer, Salao Nobre & tent Fri, Sep 28 2018,14:00 Fri, Sep 28 2018,15:00
Ngan Tran
CLS
France
ntran@cls.fr