Accuracy of Global Comparisons Between Altimetry and Tide Gauges

Pierre Prandi (CLS, France)

CoAuthors

Guillaume Valladeau (CLS, France); Michaël Ablain (CLS, France); Nicolas Picot (CNES, France); Jean-Damien Desjonquères (CNES, France)

Event: 2015 Ocean Surface Topography Science Team Meeting

Session: Science I: Mean sea level monitoring: how to reconcile altimetry, tide gauges, land motion and other in situ observations?

Presentation type: Type Oral

Quality assessment of altimeter data on the long-term is critical when one is looking for climate signals. Tide gauges measurements provide external and independent Sea Surface Height measurements which are used to check the quality and stability of altimeter sea levels. Comparisons to tide gauges are either performed at dedicated and carefully monitored calibration sites or through global analyses where a much larger set of in-situ stations is used. The main interest of both techniques is the detection of any altimeter drift or sudden bias.

The latter class of methods is based on existing tide gauges networks (GLOSS/CLIVAR, PSMSL, REFMAR), quality controlled and corrected to provide a physical measurement comparable with altimetry measurements. Results are highly dependent on processing choices like station selection, altimetry collocation, geophysical corrections for both in-situ and altimetry data. In the present study, we look for the source of observed discrepancies between tide gauges and satellite altimetry: do they reflect errors in satellite altimetry or tide gauges networks.

Results from comparisons between TOPEX/Poseidon, Jason-1 and Jason-2, which define the climate sea level record, and in-situ stations are considered here. We try to separate true altimetry problems from artifacts linked to in-situ events. This represents a new step in establishing the accuracy of our methodology for performing global comparisons between altimetry and in-situ.
 

Oral presentation show times:

RoomStart DateEnd Date
Grand Ballroom 2 Tue, Oct 20 2015,14:30 Tue, Oct 20 2015,14:45
Pierre Prandi
CLS
France
pprandi@cls.fr