Mobile version

New, accurate, homogeneous multi-satellite products

Pierre-Yves Le Traon, Françoise Ogor, Joel Dorandeu (CLS, Space Oceanography Division, France)

Merging data from different altimeter missions provides better space-time sampling of ocean features, needed for accurate monitoring of the ocean circulation. Such merging requires intercalibrated, homogeneous, validated, multi-satellite data sets.

Our group routinely performs this work on TOPEX/POSEIDON (T/P) data (GDR-Ms, distributed by AVISO), and ERS-1 and ERS-2 (OPRs distributed by CERSAT). For these three missions, altimetric corrections are homogeneised and the more precise T/P data are used to correct for ERS-1/2 orbit error. In practice, the computation is done by minimising the differences between T/P and ERS-1/2 measurements at crossover points (Le Traon et al., 1995a).

In 1995, AVISO distributed an initial two years of T/P data and one year of ERS-1 data (Le Traon et al., 1995b). A more complete dataset was recently distributed : four years of T/P data and three years of ERS-1 (first phase, with 35-day repeat period, and two 168-day-repeat-period cycles). The ERS-1 and ERS-2 data for the fourth year of T/P (second 35-day phase, the tandem mission) will be distributed by the end of 1997.

For the new data set, we used the T/P data recently reprocessed by AVISO (GDR-M version-C) using the JGM-3 orbit and CSR 3.0 tidal model. Some of the altimeter corrections used for the ERS-1/2 OPRs (ocean tide, dry troposphere, inverse barometer) were updated to make them homogeneous with T/P. The ERS-1/2 orbit error correction method was slightly improved, and with these more accurate initial data the ERS-1/2 orbit error can now be estimated to within 2 cm, comparable to the accuracy of the T/P orbit (Le Traon and Ogor, 1997). This is shown via theoretical analysis of the adjustment error and analysis of sea surface height differences at crossover points and along repeat tracks (see figures). The corrected ERS-1/2 data can be combined directly with the T/P data to derive better resolution, and hence better accuracy, for mapping the ocean signals. This is necessary for analysing ocean mesoscale features, for example.

As with the previous data delivery, these homogeneous T/P and ERS-1/2 data are distributed by AVISO on
CD-ROMs. The files are simplified and easy-to-use: CORrected Sea-Surface Heights (CORSSHs) and Sea Level Anomalies (SLAs). SLA data are also available through anonymous FTP.

 

Units are in cm from 2 cm (yellow) to 32 cm (grey). The T/P and ERS-1 rms sea level variabilities are in excellent agreement. This shows that the ERS-1 orbit error has been reduced to a level comparable to T/P orbit error (2 cm).

Acknowledgements

The multi-mission data were prepared with funding from the Midi-Pyrénées Regional Council, the European Commission (via the AGORA project) and the French space agency (CNES)

References:

  • Le Traon, P. Y., P. Gaspar, F. Bouyssel and H. Makhmaraa, 1995. Use of TOPEX/POSEIDON data to enhance ERS-1 data, J. Atm. Ocean. Tech., 12, 161-170.
  • Le Traon, P.Y., P. Gaspar, F. Ogor, and J. Dorandeu, 1995. Satellites work in tandem to improve accuracy of data, EOS, Trans. AGU, 76, 385,389.
  • Le Traon, P.Y. and F. Ogor, 1997. ERS-1 orbit improvement using TOPEX/POSEIDON: the 2 cm challenge, J. Geophys. Res.
EnglishFrançaisEspañol
Rss feedsContactPartnersFAQLexiconMobile
You must enable cookies in your browser preferences to save the modifications
You are using an older version of Internet Explorer, please update to take full advantage of Aviso+ features

Customize the home page

View all widgets
-->
Reduce display
Public profile
User profile

Select/Deselect widgets

Discover AVISO+

Customizable home, reading tools, products search guide, etc.. Discover step by step the features of the new site AVISO+.

Customizable homepage

The new home page is composed of blocks called "widgets".

Rearrange the blocks with a "Click & Drop".

Hide a widget with the cross at the top right. Reset or add a widget with the "wrench" icon. The "User" and "Public" profiles offer a predefined organization.

All the modifications are automatically saved as cookies on your machine so as to enable you to have your own specific AVISO+.

Reading tools

Ease your reading by choosing the page background colour (black/white) and/or by modifying the font size.

Browsing menu and breadcrum trail

To ease your browsing through AVISO+, you can use at any time the main banner items with the interactive submenus or use the browsing menu on the left side of the screen (it is open by default). For more readiness of the page contents, you can fold and unfold the browsing menu by clicking on the tab. At any time you can know where you are thanks to the browsing menu or the breadcrum at the top of the page.

Products search guide

The first submenu of the "Data" banner item leads you to a new search form enabling you to find quickier the product that suits your needs. The list of results is updated according to your selection criteria.

AVISO+ Multimedia

The first submenu of the "Multimedia" banner item leads you to AVISO+ collections of images and videos linked to altimetry and its applications. Have a nice visit!