Alticore

Presented by
Stefano Vignudelli
Consiglio Nazionale delle Ricerche
Italy
Satellite
ALTImetry
for
.. Special thanks to L. Roblou,
J. Bouffard,
H. Snaith,
P. Cipollini,
S. Lebedev
A. Kostianoy
A. Sirota
J. F. Cretaux
R. Mammedov
COastal REgions
Outline
Context & Motivation
ALTICORE in a nutshell (who, what, where, how)
Lessons learned
Use of coastal altimetry (who, for what, how)
Summary
with more technical details coming up in Working Groups …
¾ Roblou ( IB & Tides & Editing)
¾ Snaith (Data & Editing)
¾ Bouffard & Cipollini (Currents)
Terminology – What do we mean by “Coastal Altimetry”?
Altimetry over that ocean domain close to land
where standard processing is problematic
Information is somehow hidden and must be
recovered by ad hoc techniques
Why “Coastal Altimetry” now?
A good thing: fully exploitation of huge data volumes produced by missions
- Almost two decades of altimeter data …long-term series are great!
Interesting fact: Coastal zones are of strategic importance
- over 35% of the European Union population lives near the sea
- valuable source of food and raw materials
- vital link to transport and trade
- host valuable habitats and landscape
- favored destination for leisure
To be noted: Data assimilation by models is transforming the use of data
- Altimeters can “see” in all weather day/night
A hope at horizon: progresses in technology promise better resolution capability
- New techniques (Delay-Doppler, Interferometry, Reflectometry)
- New concepts (formation flying)
There are solid motivations for investigating …
Which problems near coasts?
1st: proximity of land
effects: no measurements at all (if the satellite approach from land)
land contamination of footprints (if close to shoreline)
Rms difference between radiometer and model
Jason (ECMWF) + GFO (NCEP)
mm
Help by R. Dussurget
SYMPHONIE Coastal Model
Current field at 50 m depth
NW Mediterranean
Courtesy: P. Marsaleix
2nd: complexity of the context
effects: greater inhomogeneity of sea state within the footprint
inadequacy of even failure of some auxiliary corrections
(e.g. Wet Tropo, IB, Tides)
Which actions?
Pre-processing
- Revisiting the conversion of the radar altimetric signal to measurements
(new re-tracking system)
Post-processing
- Reinventing the “processing” strategy (quality control)
We started with
- Integrating local knowledge (new corrections)
this approach ..
Genesis of ALTICORE
Built on precursor ALBICOCCA project
ALtimeter-Based Investigations in COrsica, Capraia and Contiguous Areas
ALBICOCCA was a joint France/Italy/UK effort supported by CNES/ASI
(2001-2004)
Focus on TOPEX/Poseidon mission at first and then extension to all
NW Mediterranean proposed as
the “operational lab” for coastal altimetry
Backward reanalysis of standard products
- data source: CTOH (LEGOS)
- 1 Hz at first
A revised post-processing strategy
- Editing and reconstruction
- MOG2D-MedSea (high-freq signal de-aliasing)
- Vertical reference frame (local MSS)
Incubator of the X-Track coastal altimeter processor
(Author: L. Roblou)
ALTICORE – WHO we are
L. Roblou
Now at
LEGOS
Sharing knowledge across organisational
France
and national boundaries …
… but more importantly across disciplines
(oceanography, remote sensing, modelling, information technology, etc.)
S. Vignudelli
G.P. Gasparini
C. Galli
E. Lazzoni
H. Snaith
P. Cipollini
F. Venuti
F. Lyard
J. Bouffard
J. F. Cretaux
UK
Now at
ECWMF
France
CNR Italy
… and drawing developing countries into the project brings
their local expertise (tidal modelling, in situ measurements
for validation/calibration, etc.)
A. Kostianoy
N. Sheremet
A. Ginzburg
E. Kuzmina
S.
A.
D.
S.
SIO Russia
GC
Lebedev
Sirota
Medvedev
Khlebnikova
Russia
R.
K.
A.
T.
Mamedov
Ismatova
Alyev
Nabijev
IG Azerbaijan
A project funded by
EU under Cooperation
Program - INTAS
(2007-2008)
ALTICORE – WHAT, HOW and WHERE
Remember two fundamental keywords: more and better data
… but more importantly add the new one: easy access
.. and build capacity in coastal altimetry on Eastern countries
with two priority topics for action
in the NW Mediterranean:
- Use of higher-rate data, no re-tracking
- Multi-mission configuration analysis
with three priority topics for action in
the other regional seas:
- Getting the local knowledge
(in situ data, regional models, etc.)
- Applying ALBICOCCA methodologies
- Exploring the adoption of RADS data sets
with Web Services and Grid concepts
… also incubator of other initiatives
ALTICORE – room for new projects and pilot sites
COASTALT project
- Development of radar altimetry data processing in the oceanic coastal zone
- funded by ESA (more from J. Benveniste & P. Cipollini)
• MARINA proposal
- MARgin INtegrated Approach - On monitoring the dynamics of the coastal
ocean through an integrated approach using in situ measurement, improved
high-resolution altimetry and ocean modelling
- submitted to Eumetsat/CNES RA (more from L. Roblou)
ALTICORE-Africa workshop (April 2008)
- Coastal dynamics from altimetry and high- resolution satellite data
- funded by Royal Society UK (more from P. Cipollini)
ALTICORE-India pilot study (since 2007)
- to replicate coastal altimetry around the Indian coasts
- joint research work involving NIO and INCOIS
Buoy Locations
and now in the next slides some
examples of the lessons learned …
Starting point … really no data ?
Standard editing strategy too much conservative
Lessons learned I – Playing with flags
Some data flagged as “bad” would be recoverable
simply turning off RADS flags
Lessons learned II – Beyond flags: new editing strategy
Screening profiles rather than single values
Reconstructing /extrapolating profiles where possible
Much more data on average than using standard editing
(more in “Data editing” session …)
Lessons learned III – Replacing global tidal models
Example of regional tidal model
from HRC (Russia)
Difference of order of meters when
compared with GOT00 (global)
Tidal correction is
problematic
White Sea
cm
..Mog2D-Medsea … the regional
solution for the NW Med Sea
with better mapping of Hi-freq
High resolution
Mog2D mesh
More in “Tides” & “IB” sessions …
Lessons learned IV – Using new vertical reference frame
Sea Level Anomaly computed from standard MSS is good
for deep basin but not for shelves and slopes
A new method to compute a local MSS
(more in “Data Editing” session …)
Lessons learned V – More in quantity and quality
Nearer coasts but even in open sea
This promises a better monitoring of the
Liguro-Provencal Current
which flows very close to the coast
and exhibits a small spatial extension.
(Bouffard et. al. 2008, submitted to JAOT ..)
Lessons learned VI – Exploiting a multi-mission scenario
Non-homogeneity between missions is the major problem
… Large-scale orbit error is the dominant component
LSER methodology for regional applications, Bouffard et al. 2008, GRL in rev.
Example of comparison of multi-mission altimetry at Genoa sea level station
Multi-satellite altimetry agrees well with the in
measurements even at time scales shorter than seasonal.
situ
Lessons learned VII – Disseminating data efficiently
Interoperability:
Not only a technical question,
but a cultural issue !
OPenDAP + netCDF in coastal altimetry data management ?
(more from H. Snaith in “Data” WG)
e.g. we tested access to data on remote sites from within Matlab code
With an “eye” to possible users and applications …
First the user, then the user, finally the user (GEOSS)
Requirements for operational use
- Easy Access
- Product Quality
- Service Reliability
- Service Sustainability
- Fit for Purpose
.. to deliver information (not data) to “end-users”
Coastal altimetry at early R&D stage
Data-integrators and modellers in the best position to exploit data
(operational oceanography moving from deep oceans to coasts)
next slide shows an example
Water levels of high interest to private & public communities
-27
KASHAGAN Oil Field
-29
-28
Sea Level (m)
-26
-25
The Caspian Sea Level Variability
by instrumental measurements
(1837-2005)
1840
1860
1880
1900
1920
1940
Time (year)
1960
1980
2000
.. But no GLOSS-compliant
stations!!!
A bottom pressure in operation soon
T/P Jason-1
Benefits from satellite
altimetry, but stakeholders not sufficiently
aware of it or familiar with it.
CASPINFO Supporting Action (funded by EU)
( CASPIAN SEA ENVIRONMENTAL AND
INDUSTRIAL DATA & INFORMATION SERVICE)
Caspian ..lake or sea ..
Taking benefit from other experiences
Rivers
Lakes
Ice
..and even wetlands
Coastal altimetry shares some
issues with other targets
(e.g. retracking)
Summary
Existing initiatives such as ALBICOCCA/ALTICORE have paved the way
to coastal altimetry … and we have learnt a number of lessons:
lessons
- Need specialized processing
- Much improved corrections now possible but not everywhere
- Promote along-track data rather than gridded products
- Rethinking data management is crucial to success
(measured in terms of users exploiting the data)
- International cooperation is essential
but we still need to improve coastal altimetry
- Optimizing signal to noise ratio (developing specialized re-tracking,
to go closer coasts, improve measurement accuracy and precision
- like in COASTALT)
- Testing new sensor concepts (constellations, SWOT,
Ka-band Altimeter, Delay-Doppler Altimeter, - see SAMOSA)
Coastal altimetry should become part of any coastal observing system
- we need to merge in situ, modeling and remote sensing
to study local dynamics
Essential message:
This newly formed community of "coastal altimetrists“
must be encouraged to work together