Analysis of the 58.77-days signal observed on the MSL derived from Jason and TOPEX data

Lionel Zawadzki (CLS, Space Oceanography Division, France)

CoAuthors

Michaël Ablain (CLS, Space Oceanography Division, France); Loren Carrere (CLS, Space Oceanography Division, France); Nicolas Picot (CNES, France); Mathilde Cancet (Noveltis, France); Florent Lyard (LEGOS, France); M. Joana Fernandes (Faculdade de Ciências, Universidade do Porto, Portugal); Richard Ray (NASA Goddard Space Flight Center, USA)

Event: 2014 Ocean Surface Topography Science Team Meeting

Session: Tides, internal tides and high-frequency processes

Presentation type: Type Poster

Mean Sea Level (MSL) is one of the main signals of interest for physical oceanographers. Since the beginning of the altimeter mission TOPEX/Poseidon, followed by Jason-1 and Jason-2 on similar orbits, MSL products became essential to the comprehension of Global ocean circulation.
Recent works on Global MSL time series highlight a strong 58.77-days signal on Jason-1 and Jason-2 whereas it is smaller on TOPEX/Poseidon. The present study shows this signal is the aliasing of a higher frequency error inherited from the tide model correction: the semi-diurnal wave S2. Several tide model corrections have been compared including GOT (Goddard/Grenoble Ocean Tide, GSFC/NASA) and FES (Finite Element Solution, LEGOS/Noveltis/CLS).
Results suggest TOPEX/Poseidon MSL -without tide corrections- contains an error due to the semi-diurnal wave S2. It is then assimilated to tide model corrections using TOPEX/Poseidon data. When these corrections are used in the computation of TOPEX/Poseidon MSL, most of the error cancels. However, this error is communicated to Jason-1 and Jason-2 MSLs, which explains why it is stronger for these missions than for TOPEX/Poseidon. The analysis also highlights the efforts made to remove this error in the latest ocean tide models.
 
Lionel Zawadzki
CLS, Space Oceanography Division
France
lzawadzki@cls.fr