COASTAL ALTIMETRY AT THE CENTRE DE TOPOGRAPHIE DES OCEANS ET DE L HYDROSPHERE

Transcription

1 COASTAL ALTIMETRY AT THE CENTRE DE TOPOGRAPHIE DES OCEANS ET DE L HYDROSPHERE Florence Birol, Caroline Delebecque, Laurent Roblou, Sara Fleury, Rosemary Morrow, Fernando Niño and Guillaume Pernot CTOH: French altimetric data service 1) maintain and distribute homogeneous altimetric data bases over all surfaces 2) help scientific users to develop new altimetry applications, 3) contributes to the processing and management of altimetric data for "emerging" research domains, 4) DEVELOP AND DISTRIBUTE REGIONAL ALTIMETRY PRODUCTS FOR COASTAL APPLICATIONS

2 CTOH coastal tools Topex R&D Roblou et al., 2010 GFO Envisat Jason-1 Jason-2 CTOH global data base: Merged GDR and additional corrections Quality control X-TRACK tool: Ø 1 Hz or higher frequency sampling Ø Specific editing + correction reconstruction Ø Global/regional (where available) dealiasing corrections Ø Local MSSH computation Post-processing based on user defined criteria: period of MSSH computation, filtering, FES2004 GOT4.7 Mog2D global Mog2D/TUGO regional models where available Along-track SLA recomputed on a regional basis

3 CTOH regional products Already distributed: Ø 1 Hz products, Netcdf format: - SLA along a nominal ground-track, - MSSH consistent with SLA - geophysical (tidal and DAC separetely) corrections included Ø 12 different regions available Ø Satellite missions (homogeneous processing): - T/P, Jason-1, T/P & Jason-1 combined, - Envisat and GFO (Western Tropical Pacific, the North Indian Ocean and the North East Atlantic for the moment) - Jason-2 available soon (work on the editing underway) Ø For each region and each mission (4 data sets): - corrected with FES2004 or GOT4.7 (if no regional model available) - alongtrack filtered and non-filtered SLA

4 CTOH regional products: Example of the Equatorial Western Pacific Ocean for Jason-1 CTOH Standard product 100 % of available data 70 RMS(SLA) in cm

5 CTOH regional products: Example of application Spatio-temporal structure of the LPC Current (NW Mediterranean Sea) August: LPC decrease Geostrophic velocity anomalies from 15 years of T/P and Jason-1 1 Hz data à Monthly climatology of: - SST (AVHRR) - Current anomalies (altimetry) LPC Current circulation December: LPC increase From Birol et al., 2010 Also poster by Leger et al.

6 What s new? Ø X-TRACK now implemented in an operational processing chain for the CTOH service. Ø New web site: Ø Regional archives updated Ø More regions available (depending on the requests) Ø Distribution of alongtrack filtered and non-filtered SLA Ø Reprocessing of Jason-1 (GDR-C) and T/P & Jason-1 combined for all areas Ø Diagnostics (regional maps of rms and % of data available) added on the web site for all SLA products

7 What s new? FES2004 or GOT4.7 in the Indonesian area? RMS(SLA) corrected with FES2004 RMS(SLA) corrected with GOT m 0

8 What s new? One year ago Now Available areas via ftp Ongoing Processing ~ 50 scientific users (half from Europe, half from Asia and America) à Feedback on the product quality

9 Perspective: HR SLA product Distance from the coast (km) March Hz SLA (no filter) 20 Hz filtered - 1 Hz cutoff frequency Time March 2007 J1 Track 146 Average distance from the French coast (first available data): km for 1 Hz J1 SLA product km for 20 Hz J1 SLA product (coherent quality) 1 Hz SLA (no filter)

10 LPC Current circulation Winter XTRACK 1Hz Monthly climatology of: - SST (AVHRR over the period ) - Cross-track geostrophic current anomalies (altimetry T/P & Jason-1 over the period ) - Question: Amplitude Are of the the seasonal small variations scale stuctures increased recovered - from More HR information data realistic? close to the coast à Validation against in-situ, - satellite Smaller scale observations structures and regional models Winter 10 Hz filtered Also poster by Roblou et al.

11 Perspective: Regional product of tidal harmonic constants derived from XTRACK alongtrack SLA Along-track harmonic analysis computed from Topex- Poseidon/Jason series ð Along-track amplitude, phase and error for different tidal constituents ð Local tidal modeling/ assimilation in coastal and shelf seas Product already used in COMAPI project

12 Perspective: Regional gridded maps of SLA An example of mul-- sensor comparison Satellite imagery may provide punctual information on fine scale dynamics Renaud XTRACK-OI (50km) Finer-scale structures in regional maps Steeper SLA gradients Dipoles visible near the slope Presentation by Dussurget et al. AVISO MSLA

13 Conclusion ü Strong connection with various scientific investigators ü The feedback we get from CTOH regional data users for marginal/coastal applications helps us: à to understand the users needs and to define products à to improve the data processing à to analyze the potential applications and/or limitations ü Regional product of HR SLA (same format than 1hz products) and tidal harmonics available soon à validation of HR SLA underway in different regions ü Ongoing work on the definition of a new MSSH product and on regional gridded products ü Any request? ctoh_products@legos.obs-mip.fr