Global Assessment of TOPEX reprocessed products (Release 5)

Hélène Roinard (CLS, France)


Sabine Philipps (CLS, France); Sylvie Labroue (CLS, France); Michael Ablain (CLS, France); Pierre Thibaut (CLS, France); Jean-Damien Desjonqueres (CNES, France); Nicolas Picot (CNES, France)

Event: 2015 Ocean Surface Topography Science Team Meeting

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

Presentation type: Type Poster

The TOPEX/Poseidon mission was the first precise altimeter mission specially designed for studying the circulation of the world’s oceans. The TOPEX/Poseidon mission furnished altimetry data for 13 years (1992 – 2005). Equipped with a redundant main altimeter (TOPEX) and an experimental altimeter (Poseidon-1, which was operated roughly one cycle in ten), altimeter data were first furnished by the TOPEX side-A instrument. Nevertheless changes in the side-A PointTarget Reponse (PTR) degraded (from mid-1996 onwards) progressively the altimeter measurements [Hayne and Hancock, 1998]. The main impacts were an increase of Significant Wave Height (SWH), an increase of range rms, and an error on range estimate. Sea State Bias (SSB) was also impacted (as it is based on SWH). In February 1999, TOPEX side-A was turned off and TOPEX side-B was turned on. In order to correct for this PTR drift of TOPEX-A a retracking of the data is necessary. Several retracking releases have been computed over the last years, those analysis have been presented in previous OSTST sessions.

The latest retracking release “Retracked GDR Release 5.0” computed by P. Callahan is an evaluation release of the TOPEX Retracked GDR (RGDR) covering cycles 21 to 364. Retracking has been completed for fixed skewness values of 0 and 0.1, as well solving for skewness. The results presented here are only covering data with skewness equal to 0.1. Retracking provide corrected SWH and range measurements.

Hereafter, the impact of the retracking is evaluated. Therefore only parameters from the retracking (range, SWH) or based on retracked parameters (SSB) are compared with previous data version. The reference parameters are non retracked data used in AVISO2014 products (which are based on MGDR products concerning altimeter parameters) and updated geophysical and orbit standards. The new solutions are also compared with Jason-1 data. Furthermore mesoscale performances (SSH differences at crossovers) and global mean sea level are also computed and compared to AVISO 2014 standards.

Poster show times:

RoomStart DateEnd Date
Grand Ballroom Foyer Thu, Oct 22 2015,11:00 Thu, Oct 22 2015,18:00
Hélène Roinard