Developing radar altimetry in the oceanic coastal zone ... · PDF fileThe COASTALT Project...

The COASTALT Project IGARSS 2008 Boston, 6-11 July www.coastalt.eu

Developing radar altimetryin the oceanic coastal zone:

the COASTALT project

Paolo Cipollini (NOCS, UK), Henrique Coelho (Hidromod, Portugal),Joana Fernandes (U Porto, Portugal), Jesus Gómez-Enri (U Cádiz, Spain),

Christine Gommenginger (NOCS, UK), Cristina Martin-Puig (Starlab, Spain),Stefano Vignudelli (CNR, Italy), Philip Woodworth (POL, UK),

Jérôme Benveniste (ESA/ESRIN, Italy)

+ the whole COASTALT crew!


COASTALT - a Coastal Zone Product Study

• At end of 2007 ESA launched an ITT for a 18-monthresearch and development activity.

• Winning proposal is COASTALT lead by NOCS, withCNR-IBF/Pisa, NERC/POL, Univ. of Cadiz, StarlabBarcelona– Univ. Porto and HIDROMOD now joining on contract extension

• COASTALT started in Jan 2008• It is done in coordination with CNES which is funding a

parallel study in France, named PISTACH.– PISTACH consortium lead by CLS

www.coastalt.eu


COASTALT - objectives• COASTALT aims to lead to the definition, specification

and prototyping of a new pulse-limited radar altimetrycoastal zone product.

• In COASTALT this is done over a number of studyregions:– NW Mediterranean (incl Corsica Channel)– West Britain– Portugal Coast

• The new product is eventually destined to becomeoperationally processed by ESA– including the reprocessing of all the ESA Radar Altimetry archive

(ERS-1, ERS-2, ENVISAT)– exploitation of CryoSat and Sentinel-3 over the coastal zone– PISTACH focuses on NASA/CNES Jason-1, Jason-2 instead


COASTALT - structure

Six Work Packages:1. user requirements for a pulse-limited radar altimetry

product (user survey)• Completed - main recommendations illustrated in next slides

2. improvement of corrections3. development of ad-hoc retracking model and processor

prototyping4. specification of Level 2 output coastal product format

and contents, and a product user handbook,5. validation and performance assessment,6. outreach.


PISTACH

• 22-month (nov 07 sept 09) project funded by CNES andlead by CLS (with LEGOS, CEMAGREF, IRD)

• Objectives:– Definition of users needs– Definition of dedicated algorithms:

• Retracking• Local/regional model for corrections (tides, bathy, atm.

forcing, …)• Radiometer wet corrections• Model dry and wet correction• SSB

– Realization and operation of the prototype during 1 year

• First products to be delivered in 2008 (autumn)

• Contact: [email protected]

Prototype Innovant de Système de Traitementpour les Applications Côtières et lʼHydrologie


WP1 - product requirements• In short: what do users expect from a coastal altimetry

product?– Parameters of interest– Space/time resolution, coverage– Accuracy/precision requirements– Quality control, auxiliary/ancillary data– Time of delivery, ways to access data– File formats

• User surveys distributed Dec07-Jan08 by PISTACH, Feb-Mar 08 by COASTALT– 50+ replies overall– Cover a good spectrum of users (both research and operational,

both public and private)– STARLAB (L. Moreno - C. Martin-Puig) carried out analysis


WP1 Product requirements - 1

Modelling community is an important user communityWind and Waves matter to a good share of the users

Some scope for near-real-time or even real-time delivery ofcoastal altimetry

RECOMMENDATIONS:• products to be provided along-track;• include SSH, SWH and Wind sped• include both the 1 Hz posting rate and 18 Hz (ENVISAT)• include data as close to the coast as possible, even

when none of the main estimated parameters (height,significant wave height and wind) are considered reliable

• develop delayed products, but compatible with thedelivery of near-real-time and real-time data


WP1 Product requirements - 2• Improve corrections (including local corrections) and

retracking so that accuracy and precision areoptimized

• Provide SSH, anomaly and mean value, and a coastalMDT

• Provide quality flags together with all the separatecorrections and

• Easy to merge across missions cross-calibration ofSSH, wind and wave information from Envisat with thosefrom other altimetric missions

• NetCDF format and distributed both via FTP andOPeNDAP;

• DVD distribution should be retained for those userswith bandwidth constraints


• Reprocessing is expected to improve in precision (correlationgeophysical parameters and corrections )– include all shelf areas, where tides are problematic– include some specific basins such as Mediterranean Sea

• The coastal domain is defined as:– all track segments with distance from the shoreline <200 km;– all track segments with distance from the shoreline between 200 and 400

km and bathymetry shallower than 5000m;– all continental shelves including the shelf slopes;– all marginal, enclosed and semi-enclosed seas like Mediterranean Sea

WP1 Product requirements - 3

(map from PISTACH)


WP2 - improving corrections• Wet Tropospheric correction:

– Extending (linking) models withradiometer observations

– Modelling/removing land effect– GPS-based wet tropo

• Dry Tropospheric correction:– Investigate specialized models like

ALADIN (Météo-France)• Ionospheric corrections

– Extend dual-freq open oceancorrections using GIM model(based on GPS)

• IB and HF dealiasing– Investigate and use local models

• Also need better data screeningand editingExample: Difference between a local tidal model

and a global one (GOT00) over the White Sea(courtesy of S. Lebedev / A. Sirota)


Tides - some options• Reprocess altimeter data with a more recent global model

– GOT4.7 (R. Ray, soon GOT5.0) or EOT08a (W. Bosch)• Employ a global model with additional tidal analysis/filtering

– Akin to developing a regional model, takes time!• Assemble a set of regional tide models

– NW Mediterranean– regional T-UGO-Medsea model (F. Lyard).– West of Britain – newly developed POL 1 nm model for the NW

European shelf.– West of Portugal - Mohid model (Hidromod, Lisbon)

• In the long term: develop a complete set of new regional modelsdynamically consistent at their boundaries with the global models (abig endeavour for the tidal modelling community)


WP3 - retracking

ENVISAT pass 294(descending)

Cycle 39

Cycle 40

Cycle 41Bonifacio Strait

CapraiaIsland

BonifacioStrait

Capraia


Elevation/depth: 413,44 mLand/Ocean flag: LAND (3)

Pass

294

Pass

294

Pass

22

Pass

22








Elevation/depth: -20,17 mLand/Ocean flag: LAND (3)


But… at full rate (18Hz)…


Elevation/depth: -40,07 mLand/Ocean flag: OCEAN (0)


Elevation/depth: -23,78 mLand/Ocean flag: OCEAN (0)


Elevation/depth: -22,08 mLand/Ocean flag: LAND (3)




WP3 - retracking in COASTALT - 1

• We aim to use a model-based tracker, as this candirectly estimate the geophysical parameters

• In coastal areas, exposed sandbanks, coastal flats andcalm waters will give a bright target

• but the return from the open water portion will still beBrown-like

• We can model the bright targets as narrow Gaussianpeaks, so the waveform will be:


• But the bright targets migrate through the waveformsin a predictable way

At time t the target is at

• So if we track batches (sequences) of waveforms we willget better estimates of the target parameters and avoidmisclassification of noise as bright (or dark) targets.

• We call this ʻsequentialʼ retracking

WP3 - retracking in COASTALT - 2


A rosy future for coastal altimetry?

• A good amount of research is being carried out and somehas been done already; more is needed, but severalgroups are working on it

• COASTALT (ESA) and PISTACH (CNES) are paving theway to operational coastal altimetry

• The US altimetry community got quite interested too andCIOSS and NOAA organized the 1st Coastal AltimetryWorkshop last February in Silver Spring, Maryland– ~50 scientists including many from Europe– see

http://cioss.coas.oregonstate.edu/CIOSS/altimeter_workshop.html• This will be followed up…

• Showcase of results from COASTALTand PISTACH Projects

• Wed-Fri of week before Nice OSTST(which is on 10-14 Nov)

– Wed 5 Nov: COASTALT Project meeting– Thu 6 - Fri 7 Nov: open workshop

• Also includes ALTICORE end-of-projectsummary

• Aims to follow-on to the many issuestouched in the 1st workshop, such as:

– Consolidate results on improvement ofcorrections and editing

– Discuss first results on coastal retracking– Promote future cooperation

• Findings/recommendations to be reportedat OSTST

• Organizers: S. Vignudelli (CNR),J. Benveniste (ESA), N. Picot (CNES),P. Cipollini (NOCS)

www.coastalt.eu/pisaworkshop08

2nd Coastal Altimetry WorkshopPisa, Italy, (5)-6-7 November 2008

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