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• Welcome to OCTAS study course arranged in
  cooperation with the NKG Working Group for Geoid
  Determination and the University of Copenhagen

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GOCINA and OCTAS
GOCINA, Geoid and Ocean Circulation In the North
Atlantic, financed by EU OCTAS,Ocean
Circulation and Transport Between North Atlantic
and the Arctic Sea, financed by the Norwegian
Research Council http//www.gocina.dk
http//www.octas.statkart.no
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Objective
Improve and enhance the European and Norwegian
capacity in Earth Obseravtion Technology for
exploitation of ongoing space based projects
within climate modeling
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GOCINA partners
KMS, Kort og Matrikelstyrelsen, DK NMA, Norwegian
Mapping Authority, NO UEDIN, University of
Edinburgh, UK UREADES, University of Reading,
UK NERSC, Nansen Environmental and Remote Sensing
Center, NO CLS, Collecte Localisation Satellites,
FR
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OCTAS partners
NMA, Norwegian Mapping Authority NLH,
Agricultural University of Norway NERSC, Nansen
Environmental and Remote Sensing Center NTNU,
Department of Geomatics UiB, University of
Bergen (UiO, University of Oslo) External
partners KMS, Kort og Matrikelstyrelsen, DK OSU,
Ohio State University, US UNR, University of
Nevada Reno
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Main objectives
Determine Mean Dynamic Topography, MDT, for ocean
circulation and transport studies. To achieve
this one needs A high precision geoid model
for the study area A Mean Sea Surface model,
MSS Investigate the importance of an improved MDT
on ocean circulation models
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Study-area
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Common to both projects
Interdisciplinary combination of physical
geodesy, satellite technology and oceanography
Combining geoid models based on updated (marine)
gravity data sets with mean sea surface models
from satellite altimetry and models of the mean
dynamic topography Develop integrated techniques
for analysis of geoid and MDT. Improve
predictions thorough better MDT models
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Differences
GOCINA Use of existing knowledge and expertise,
project duration 3 years OCTAS Use and
establishment of new knowledge and expertise, 4
PhD students, project duration 4 years
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Workpackages
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WP objectives
Determination of a high precision
geoid Determination of a high precision MSS
model Determination of a high precision MDT model
based upon hydrographic data and ocean
models Assess the geoid, MSS and
MDT-models Integrated techniques for an optimal
combined determination of the geoid and the
MDT Investigate the impact of an improved MDT on
the ocean circulation estimate
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WP1, Geoid
Collect existing geoid-models Collect and
validate existing marine gravity data Carry out
an Airborne gravity campaign to create a
gravimetric reference data sate and to improve
the gravity coverage Combine marine and airborne
data, adjust erroneous data Compute new geoid
models
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Geoid-models
Existing models at project start NKG_Tallinn
EGG97 ARCGP EDIN2000 EGM96 New models
OCTAS_01 OCTAS_02 GOCINA_KMS_2004a
GOCINA_UEDIN_2004a
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Data coverage
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Marine data, example of errors
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GOCINA
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Adjust marine gravity data

• X-over programs, identify x-over points and
  differences
• Problem Point-organized data, must regenerate
  the marine tracks. Alternatively, interpolate to
  the desired position by collocation
• Work in progress

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GOCINA KMS 2004 Geoiden
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WP 2, Satellite-altimetry

• Collect existing MSS models
• Collect altimetry data from existing satellites,
  investigate the optimal method for computing the
  MSS
• Compute high precision detailed MSS with error
  estimate for the time period 1993-2001
• Update the MSS

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MSS models

• GSFC00
• CLS01
• KMS01
• KMS03
• CLS2004
• KMS2004

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KMS2004 Mean Sea Surface
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Satellite Altimetry

• Radar signals emitted from satellites in low
  earth orbits are being reflected from the earth's
  surface. Combined with accurate tracking of the
  satellites this determines the instantaneous
  surface of the earth. So far the technique has
  primarily been used to map the ocean surface.
• See also
• http//www.aviso.oceanobs.com/html/alti/welcome_uk
  .html

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Altimetry satellites

• Satellite Launch date Orbital
  height (km)
• Seasat June 26, 1978 800
• Geosat March 12, 1985 800
• ERS-1 July 17, 1991 800
• Topex/Poseidon August 10, 1992 1300
• ERS-2 April 21, 1995 800
• GFO February 10, 1998 880
• Jason-1 December 7, 2001 1300
• Envisat March 1, 2002 800

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Altimetry tracks
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Challenges

• Problematic areas
• Shallow water
• Islands and close to the shore
• Areas with sea ice
• Retracking may solve some of these problems

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Retracking
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Orbits

• Conflict of interests
• Long repeat period, geodesy, good geographical/
  spatial coverage
• Short repeat period, oceanography, the same
  marine areas are surveyed repeatedly with short
  repeat periods, advantageous for study of time
  dependent features
• Latitude limitations

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WP 3, Mean Dynamic Topography, MDT

• Collect existing MDT models
• Compute new MDT models
• From existing climatologic dataset
• Combine hydrographic data with altimetry
  without the use of ocean circulation models
  
• Combine hydrographic data with ocean
  circulation models

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MDT models

• Existing mdt models
• ECCO
• LEGRAND
• LEVITUS
• OCCAM
• CLS v.0-3
• GOCINA MDT models
• GOCINA_COMPOSITE v. 1,2

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WP 4, Assessment and validation of the models

• Comparison of models
• Assessment of best geoid, MSS and MDT models,
  estimation of errors
• Intercomparison of best geoid, best MSS and best
  MDT model
• Repeat this as new improved models are derived

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• Fundamental formula
• MSS-Geoid-MDT0
• This implies
• MDTMSS-Geoid
• GeoidMSS-MDT
• MSSGeoidMDT

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ResidualMSS-Geoid-MDT
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MDTKMS2004 MSS- KMS2004 geoid
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GOCINA Composite MDT
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MDT (KMS2004 MSS KMS2004 geoid)-Composite MDT
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Correlation studies
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Line correlation
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Study area
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Geoid models
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Gravity coverage
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MDT models
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WP 5, Integrated methods

• Determine geoid and (mean) sea surface topography
  by collocation, fourier and assimilation-technique
  s
• Develop integrated solution of geoid, mss and mdt
• Compute tensor gravity filed components with
  error estimate at GOCE altitude
• Investigate the effect of using simulated GOCE
  data

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WP 6, Ocean Circulation and transport

• Study heat and mass transport
• The objective of this workpackage is to analyse
  the impact of the MDT models (improved in WP4) on
  the estimates of the North Atlantic circulation
  provided by recent high-resolution ocean
  forecasting systems. The enhanced ocean mean
  transport (mass and heat), as well as seasonal
  variability will be diagnosed. The impact on the
  forecasting capabilities will be examined.

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WP7, Recommendations for integrating GOCE

• The main objective is to provide a set of
  specific recommendations, based on the concrete
  outcome of WP3, WP5 and WP6, on the approach for
  integrated geoid and MDT computations using GOCE
  data. Input to the workpackage will particularly
  come from WP 3, WP 5 and WP6.

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Status

• GOCINA in progress for more then 2 year, 1 year
  left
• OCTAS, in progress for 2 year, 2 year left
• Currently 2 PhD students and 1 Post. Doc.
• New Post. Doc. at NMA approved by Norwegian
  Research Council (Jan. 9, 2005)
• More work than expected, very time consuming,
  some delays
• Promising results, continued improvement as new
  data and models are made available

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The geoid, an important climate parameter

• Land Height-determination by GPS
• Sea MDT determination by altimetry
• Polar regions freeboard, ice-thickness
  determination by altimetry

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Marine surfaces