WP3: Task 3'1 Altimetry

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WP3 Task 3.1 - Altimetry

• Title Empirical determination of inter-annual to
  decadal sea level variations on the basis of tide
  gauge and satellite altimetry on high resolution
  for the NA and adjacent European Seas and low
  resolution globally.
• Duration Month 1-12
• Deliverables (report) D3.1 Report Annual to
  decadal sea level var.
• Partners.
• P2 - KMS, Denmark (Niels Kjær, Ole Andersen, Per
  Knudsen)
• P14 TUD, Germany (Luciana Fenoglio
• P3 - NERC-POL, UK (Philip Woodworth

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Bidston (03/2003) Guidelines

• Use Pathfinder (v.9.2) data with no inverse
  barometric (IB) correction.
• Remove tilt at each location
• Remove seasonal variation
• Compute power spectrum and detect dominant
  frequencies
• Evaluate correlation Compute auto-correlation
  function
• 50 correlation time and time of
  zero crossing
• Carry out EOF analysis in regions in European
  seas and globally 

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Regions.
North
Baltic Atlantic North Sea
Sea       Black Sea  
Mediterranean          
Different regions has different
characteristics i.e. BalticBlack Sea have narrow
straits.
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Altimetry and Tide Gauges
TOPEX/POSEIDON Data 01/1993-08/2002. All
bestcorrections applied (rangedriftgeophys) No
inverse barometer correction applied. Monthly
mean values computed. Sea level trend (tilt)
Seasonal signals removed.
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Achievements Power Spectrum (1)

Altimetry alone The Power Spectrum varies with
location

• Dominant frequency gt 12 month.
• Baltic Black Sea stands out as regionally
  consistent
• Tide Gauges confirms altimetric results.

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Achievements Power

• Altimetry AND Tide Gauge results.
• Similar power spectras obtained if similar
  periods are chosen
• For enclosed seas and continental margins
• (i.e. Stokholm vs Baltic, Cuxhaven vs North Sea
  etc.)
• Altimetry vs Tide Gauge does not work everywhere.
  
• (Trieste vs. Mediterannean is bad)
• Power Spectrum does not remain constant in time.

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Achievements Power Spectrum (2)

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EOF

• EOFs computed from altimetry
• Table shows percentage of variance explained.

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Status / Problems.
Obtained interesting comparisons of altimetry vs
TG Obtained similar power spectras over similar
periods But only very few TG data from 2000
onwards Only 7 years for TG vs Altimetry
comparison need 10years. Need Better
distribution for available TG. TG captures
inter annual variations on a wider spatial
scale In complex regions this might not be true
(Trieste) Regional EOF explains large
percentage of sea level variance In closed sea
and on continental margins. Cross-correlation
spectras needs further investigation TG spectras
varies in time.
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Whats Next.
Extend Altimetry vs TG comparison. Need More TG
data over 10 years period.
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Auto Correlation