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T3.1Optimal synergy between altimetry and in-situ dataClaire Dufau (1)Enrique Alvarez (2), Ole B. Andersen (3), Florence Birol (4), Mathilde Cancet (4), Begona Perez (2), Gilles Larnicol (1), Gennady Koroatev (5),Per Knudsen (2), Arseny Kubryakov, Marie-Hélène Rio (1)(1)CLS, France(2) OPPE, Spain (3) DNSC, Danemark(4) LEGOS-CTOH, France (5) MHI, Ukrain


T3.1 General objectives

  • Consolidate and improve the altimeter products in regional/coastal areas
  • Ensure the transfer of R&D activities to operation

link with MERSEA project (open ocean)

link with ECOOP WP2 (operational demonstration)

  • Two ECOOP regions are identified to lead specific R&D studies
    • Black Sea : CLS,MHI

Issues for Altimetry near the coasts

Standard products are not really adapted for regional use, specially near the coast due to

  • Specific dynamics over the continental shelves and shelf breaks show higher frequencies and shorter spatial scales

aliasing on lower frequencies disturbing signal quality

  • Lack of accuracy in the altimetry measure corrections essentially due to the presence of land in the footprint of the sensor

First way of improvements

  • Better management of aliasing problem
  • Improvement of the corrections near the coast (atmospheric, geophysical, etc.)
  • Use of 20Hz sampling instead of 1Hz

Two Coastal Altimetry Projects have started in Europe to investigate such issues:

PISTACH (CNES funded): since Autumn 2007, dedicated first to Jason-2 products (launching in June 08)

COASTALT (ESA funded): since January 2008, dedicated first to ENVISAT products


T3.1 Optimal synergy between altimetry and TG

Second way of improvements

    • Use of in-situ data located near the coast (Tide Gauges) for adding HF signal missing in altimetry
  • 0bjectives of T3.1:
    • Analyze consistency between altimeter data sets and TG
      • HF signals
      • Tidal corrections
      • Measurement errors
    • Estimate how HF signal in in-situ data could permit to improve altimetry
    • Develop merging techniques
    • Improve Mean Dynamic Topography in the Black Sea and IBIROOS

Production of a new regional altimeter dataset: the AVISO Black Sea product

Development of a regional multi-mission processing including

  • a higher along-track resolution (no sub-sampling) than global products
  • adapted filtering & adapted long-wave errors correction
  • a new Mean Sea Level (performed with the latest SSH dataset including new geophysical corrections )
  • a refined criterion for data selection
  • Smaller correlation scales for mapping (gridded products)




A new regional altimeter dataset in Black Sea

Global product

Regional product


Black Sea : first results of altimeter/in-situ comparison

8 coastal stations (TG) time series in 1993

and 2 in 2003 (see besides)


IBIROOS : altimetry & TG datasets

  • Altimeter datasets :
    • 2 LEGOS-CTOH products
      • With classical tidal correction (global model)
      • With regional tidal correction (regional model)
    • 2 CLS (AVISO) SLA-extended products
      • the ones developed for MERSEA
      • their very new version (not yet available though AVISO)
  • Comparison period = 2003-2005
  • In-situ data = Tide Gauges :
    • REDMAR network (provided by OPPE)
    • GLOSS/CLIVAR network (provided by CLS)
    • SONEL network
    • BODC network

IBIROOS : How to compare them?

  • WP3.1 meeting on this topic in late December
    • Each partner has proposed some diagnostics that could be done such as:

CORRELATIONS between the TG and altimetric sea level time series

From a study made by DNSC over the North Sea

From a study made by LEGOS-CTOH over the NW Med Sea


IBIROOS : How to compare them?

  • WP3.1 meeting on this topic in late December
    • Each partner has proposed some diagnostics that could be done such as:

Spectral Analysis (FFT) computed with TG and altimetric sea level time series

From a study made by LEGOS-CTOH over the NW Med Sea


T3.1 next steps are:

  • Performing altimetry & TG comparison studies over IBIROOS area
    • Datasets are just provided .. study is beginning.
    • Deadline = June 08
  • Working on merging techniques between in-situ and altimetry data
    • Deadline = August 08
  • Computing improved MDT for the 2 regions.
    • In progress
    • Deadline =August 08