Radar Altimetry Tutorial December 2 006 V. Rosmorduc, J. Benveniste, O . Lauret, M. Milagro, N. Picot J. Benveniste, N. Picot, EditorsRadar Altimetry Tutorial Radar Altimetry Tutorial Predicting climate, monitoring mean sea level, river and lake levels, global warming, El Niño and La Niña events, marine currents and ocean circulation, tides, geoid estimates, wind, wave and marine meteorology models, ice sheet topography and sea ice extent, etc. Radar altimetry can provide such a wealth of information -- and more -- from its measurements. This Radar Altimetry Tutorial describes applications, examples (data use cases) and techniques, including standard data processing, as well as the various satellite missions that have carried, are carrying or will carry a radar altimeter onboard, plus a range of altimetry products (data, software and documentation). A Basic Radar Altimetry Toolbox is also available. This is a collection of tools and documents designed to facilitate the use of radar altimetry data. It can read most distributed radar altimetry data, from ERS-1 & 2, Topex/Poseidon, Geosat Follow-on, Jason-1, Envisat to the future Cryosat missions, and can perform processing and data editing, extraction of statistics, and visualisation of results.
Acknowledgments & contributors This tutorial was produced by CLS under contract to ESA and CNES. Citation If using this tutorial, please cite: Rosmorduc, V., J. benveniste, O. Lauret, M. Milagro, N. Picot, Radar ...
Radar Altimetry Tutorial
December 2 006
V. Rosmorduc, J. Benveniste, O . Lauret, M. Milagro, N. Picot
J. Benveniste, N. Picot, EditorsRadar Altimetry Tutorial
Radar Altimetry Tutorial
Predicting climate, monitoring mean sea level, river and lake levels, global warming, El Niño and La
Niña events, marine currents and ocean circulation, tides, geoid estimates, wind, wave and marine
meteorology models, ice sheet topography and sea ice extent, etc. Radar altimetry can provide such a
wealth of information -- and more -- from its measurements.
This Radar Altimetry Tutorial describes applications, examples (data use cases) and techniques, including
standard data processing, as well as the various satellite missions that have carried, are carrying or will carry
a radar altimeter onboard, plus a range of altimetry products (data, software and documentation).
A Basic Radar Altimetry Toolbox is also available. This is a collection of tools and documents designed to
facilitate the use of radar altimetry data. It can read most distributed radar altimetry data, from ERS-1 & 2,
Topex/Poseidon, Geosat Follow-on, Jason-1, Envisat to the future Cryosat missions, and can perform
processing and data editing, extraction of statistics, and visualisation of results.
Acknowledgments & contributors
This tutorial was produced by CLS under contract to ESA and CNES.
Citation
If using this tutorial, please cite:
Rosmorduc, V., J. benveniste, O. Lauret, M. Milagro, N. Picot, Radar Altimetry Tutorial, J. Benveniste and N.
Picot Ed., http://www.altimetry.info, 2006.
Authors
V. Rosmorduc (CLS), J. Benveniste (ESA), O. Lauret (Silogic), M. Milagro (SERCO), N. Picot (CNES)
Editors
J. Benveniste (ESA), N. Picot (CNES)
Scientific committee
G. Goni (NOAA, USA), S. Laxon (UCL, UK), J.M. Lefèvre (Météo France, France), C. Maes (IRD, New
Caledonia), F. Rémy (Legos/CNRS, France), J. Tournadre (Ifremer, France)
Acknowledgments
Thanks to M. Ablain, L. Amarouche, J. Dorandeu, J.P. Dumont, P. Escudier, S. Guinehut, F. Lefèvre,
F. Mercier, P. Schaeffer, P. Thibaut, O.Z. Zanifé (CLS) for inputs and advices
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Radar Altimetry Tutorial
Contents
Introduction
Overview
1. Altimetry applications
1.1. Geodesy & geophysics
1.1.1. Bathymetry
1.1.2. Geodesy
1.1.3. Other geophysical applications
1.1.4. Tsunami
1.2. Ocean
1.2.1. Large-scale circulation
1.2.2. Ocean currents and eddies
1.2.3. Operational oceanography
1.2.4. Tides
1.2.5. Mean Sea Level rise and the Greenhouse effect
1.3. Ice
1.3.1. Ice sheets
1.3.2. Sea ice
1.4. Climate
1.4.1. El Niño - Southern Oscillation (ENSO)
1.4.2. North Atlantic Oscillation (NAO)
1.4.3. Decadal oscillations
1.4.4. Seasons
1.5. Atmosphere, wind & waves
1.5.1. Wind & waves
1.5.2. Cyclones, hurricanes and typhoons
1.5.3. Rain
1.6. Hydrology & land
1.6.1. Lake level
1.6.2. Land
1.6.3. River level
1.7. Coastal
2. Data use cases
2.1. Altimetry data processing for mesoscale studies
2.2. Western boundary currents
2.3. Temporal variations of the Amazon basin
2.4. El Niño and ocean planetary waves
2.5. Seasonal distribution of Significant Wave Height
3. Altimetry
3.1. How it works
3. 1.1. Basic Principle
3.1.2. From Radar pulse to the altimetric measurements
3.1.3. Frequencies used, and their impacts
3.1.4. Multi-mission combinationsn
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3.2. Data flow
3.2.1. Data acquisition
3.2.2. Data processing
3.2.3. Data qualification
3.3. Future technology improvements
3.3.1. Ka-band
3.3.2. Constellations
3.3.3. Interferometers
3.3.4. GNSS
4. Altimetry missions
4.1. Past missions
4.1.1. Skylab
4.1.2. GEOS 3
4.1.3. Seasat
4.1.4. Geosat
4.1.5. ERS-1
4.1.6. Topex/Poseidon
4.2. Current missions
4.2.1. ERS-2
4.2.2. GFO
4.2.3. Jason-1
4.2.4. Envisat
4.3. Future missions
4.3.1. Jason-2
4.3.2. Cryosat
4.3.3. (AltiKa)
4.3.4. NPOESS
4.3.5. Sentinel 3
5. Product information
5.1. Product information
5.2. Toolbox
6. FAQs
6.1. Applications
6.2. Altimetry
6.3. Toolbox
Glossary Radar Altimetry Tutorial
Tutorial overview
This Radar altimetry tutorial is organised into six main chapters:
1. Applications
This chapter describes the main applications of radar altimetry, both current and in development, and is
organised according to field of study.
2. Data use cases
This chapter gives some practical examples of the applications of altimetry data. The type of data to
use, the methodology and the main computations are detailed, as well as how to work with data using
the Basic Radar Altimetry Toolbox.
3. Altimetry
This chapter contains background information about altimetry techniques, how data are measured,
processed and qualified, as well as the future technology developments being studied.
4. Altimetry missions
This chapter describes the past, present and future altimetry satellites, with details about the altimetry-
related instruments onboard, their orbits and ground segments. This chapter describes the past, current
and future altimetry satellites, with details on the altimetry-related instruments onboard, the orbit and
ground segment.
5. Product information
This chapter covers altimetry products (software and documentation as well as data). It also gives
access to the Basic Radar Altimetry Toolbox.
6. FAQs
This chapter contains questions asked about the tutorial and the toolbox, applications, altimetry and
products.
In general, the deeper you go into the sub-sections, the more technical the information becomes.
This document is mainly aimed at newcomers to altimetry. For this particular audience, we suggest
beginning with a specific field of interest (Geodesy & geophysics, Ocean, Ice, Climate, Atmosphere, wind &
waves, Hydrology & land, Coastal), then having a look at the corresponding use cases, if any. The 'Altimetry'
section provides more technical information, but for an initial approach you can focus on the section headers,
where an overview is given (e.g. How altimetry works : basics).
A contents gives a general view of the Tutorial. This can be used as a doorway for advanced and expert
users, enabling them to go directly to the technical information.
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Radar Altimetry Tutorial
1. Altimetry applications
A wealth of applications are possible using radar altimetry measurements, involving most geoscience
fields and practised by more than a thousand teams of users around the world. From the 'historical'
applications (geodesy, general ocean circulation) to the developing ones (solid Earth and coastal
applications, etc) and the ones that have become classic (ocean variability, ice topography,
hydrology), altimetry has shown over and over that it is a very productive technique.
Geodesy & geophysics
Ocean
Ice
Climate
Atmosphere, wind & waves
Hydrology & land
Coastal
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Radar Altimetry Tutorial
1.1. Geodesy & geophysics
Geophysics is the study of the substances that make up
the Earth and the physical processes occurring on, in
and above it. Information derived from altimetry data
can be used to study the Earth's shape and size, gravity
anomalies (geodesy), seafloor relief (bathymetry),
tectonic plate motion and rifts (geophysics), etc.
Although often linked to plate tectonics, tsunamis are
very different, transient phenomena. However, their
impact on the sea surface can be seen by altimeters in
some cases, thus helping the study of their propagation.
Bathymetry
Geodesy
Other geophysical applications
Tsunami
Example of geophysical information extracted from altimetry (around
Italy)
(Credits University of Calgary)
Further information:
McAdoo, D., Marine Geoid, Gravity, and Bathymetry: An increasingly clear view with satellite altimetry, 15
years of progress in radar altimetry Symposium, Venice, Italy, 2006
Radar Altimetry Tutorial
1.1.1. Bathymetry estimate from altimetry
Dense satellite altimeter measurements can be used in combination with sparse measurements of
seafloor depth to construct a uniform resolution map of the seafloor topography. These maps do not
have sufficient accuracy and resolution to be used for assessing navigational hazards, but they are
useful for such diverse applications as locating obstructions/constrictions to the major ocean
currents and shallow seamounts where fish and lobster are abundant. Detailed bathymetry also
reveals plate boundaries and oceanic plateaus.
A detailed knowledge of topography is fundamental to the
understanding of most Earth processes. In the oceans, detailed
bathymetry is essential for understanding physical
oceanography, biology and marine geology. Currents and tides
are controlled by the overall shapes of the ocean basins, as
well as by the smaller, sharp ocean ridges and seamounts. Sea
life is abundant where rapid changes in ocean depth deflect
nutrient-rich water toward the surface. Because erosion and
sedimentation rates are low in the deep oceans, detailed
bathymetry also reveals mantle convection patterns, plate
boundaries, the cooling/subsidence of the oceanic lithosphere,
oceanic plateaus and the distribution of off-ridge volcanoes.
Since it is impossible to map the topography of the ocean
basins directly from Space, most seafloor mapping is a tedious
process that is carried out by research vessels equipped with
echo sounders. However, completely mapping the ocean
Bathymetry can be computed using altimetry basins at a horizontal resolution of 100 m would take about 125
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