Improved description of the ocean mesoscale variability by combining four satellite altimeters

Abstract

Data from four satellite altimeters are combined with the aim of improving the representation of the mesoscale variability in the Global Ocean. All missions [Jason‐1, ERS‐2/ENVISAT, Topex/Poseidon interleaved with Jason‐1 and Geosat Follow‐On] are cross‐calibrated previously to produce weekly gridded maps. In areas of intense variability, the rms differences between a classical configuration of two altimeters and the scenario merging four missions can reach 10 cm and 400 cm2/s2 in SLA and EKE, respectively, which represents an important percentage of the signal variance. A comparison with surface drifters shows that the four altimeter scenario improves the recovery of mesoscale structures that were not properly sampled with Jason‐1 + ERS‐2/ENVISAT. Finally, the consistency between altimetric and tide gauge data is improved by about 25% when coastal sea level is estimated with 4 satellites compared to the results obtained with 2 altimeters.

High resolution altimetry reveals new characteristics of the December 2004 Indian Ocean tsunami

“…This is due to the exceptional intensity of the Sumatra tsunami but also to a unique configuration of four altimeters flying simultaneously. Such a configuration is necessary to describe and forecast the ocean mesoscale variability [e.g., International GODAE Steering Team, 2001;Pascual et al, 2006]. It allowed us to extract the signals due to the tsunami from the background ocean variability signals.…”

“…It was also the first one to be detected very clearly by TOPEX, Jason-1, Envisat and GEOSAT Follow On (GFO) satellites [e.g., Smith et al, 2005]. The purpose of our paper is to concentrate on precise observations and detection by satellite.…”

“…Most of these signals can be removed, however, using an ocean anomaly mapping technique [e.g., Le Traon et al, 1998]. Note that this is possible only because we had at this time a very good space/time sampling of the ocean with four altimeters [Pascual et al, 2006].…”

Pathways of mesoscale variability in the South China Sea

“…The estimation of mesoscale signals is greatly improved when the data from two satellites are combined with the use of an objective mapping technique (Ducet et al, 2000). Compared to the results obtained with 2 altimeters, the MV estimated with 4 satellites has little improvement at low latitudes, where the size 5 of typical structures is relatively large (Pascual et al, 2006). It is known that altimetry measurements could be contaminated by high-frequency (HF) variability at period shorter than the Nyquist period of altimetric repeat cycle.…”

Using altimetry to help explain patchy changes in hydrographic carbon measurements

“…This data product is composed of measurements from Envisat, ERS, Topex/Poseidon, as well as Jason-1 [Le Traon et al, 2003;Pascual et al, 2006], and the approximate resolution is one week by 40 km. We consider changes in SSHA along the transects corresponding to the in situ ocean measurements.…”