Global Validation and Assimilation of ENVISAT ASAR Wave Mode Spectra

1. Global Validation and Assimilation of ENVISAT ASAR Wave Mode Spectra Saleh Abdalla, Jean-Raymond Bidlot and Peter Janssen ECMWF, Reading, UK

2. Outline: • Introduction. • Quality of ASAR Wave Mode Level 1b (ASA_WVS_1P). • Quality of ASAR Wave Mode Level 2 (ASA_WVW_2P). • Assimilation of ASAR Wave Mode Level 1b at ECMWF. • Conclusions Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

3. Introduction: • Fast delivery ASAR Wave Mode products are verified against wave model: • Level 1b  is inverted before verification. • Level 2  wavelengths exceeding the azimuthal cut-off. • Wave model used is: WAM operational at ECMWF. • Verification is done in terms of a limited number of integrated parameters: • Significant wave height (SWH), • mean wave period (MWP), • wave directional spread (WDS), • wave spectral peakedness factor of Goda (WPF), and • mean wave direction (MWD). Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

4. ENVISAT ASARWave Mode Level 1b(ASA_WVS_1P)Product Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

5. Global comparison between inverted ASAR level 1b and WAM model significant wave heights(From 11 April to 31 August 2005) Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

6. Global comparison between inverted ASAR level 1b and WAM model mean wave periods(From 11 April to 31 August 2005) Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

7. Global comparison between inverted ASAR level 1b and WAM model wave spectral peakedness factor of Goda (From 11 April to 31 August 2005) Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

8. WAM bath. WAM dissip. PF-ASAR 3.07 Time history of mean wave period bias between ASAR Level 1b inverted product and WAM. Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

9. WAM dissip. PF-ASAR 3.07 WAM bath. Time history of mean wave period scatter index between ASAR Level 1b inverted product and WAM. Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

10. PF-ASAR 3.07 Time history of daily results of ASAR Level 1b inversion. Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

11. ENVISAT ASARWave Mode Level 2(ASA_WVW_2P)Product Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

12. 100’s 10’s OK Global comparison between ASAR Level 2 and WAM model swell significant wave heights(From 11 April to 31 August 2005) Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

13. Global comparison between inverted ASAR Level 2 and WAM model swell mean wave periods(From 11 April to 31 August 2005) Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

14. Global comparison between inverted ASAR Level 2 and WAM modelswell wave spectral peakedness factor of Goda (From 11 April to 31 August 2005) Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

15. WAM bath. WAM dissip. PF-ASAR 3.07 Time history of swell significant wave height scatter index between ASAR Level 2 product and WAM. Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

16. WAM bath. WAM dissip. PF-ASAR 3.07 Time history of swell mean wave period bias between ASAR Level 2 product and WAM. Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

17. Assimilation of ASARWave Mode Level 1bProductat ECMWF Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

18. Assimilation of ENVISAT ASAR Wave Mode Level 1b Spectra • Inversion of ASAR Wave Model Level 1b spectra into ocean wave spectra. • Assimilation method is based on wave subsystems. • Cross assignment (ASAR vs. model). • Optimum interpolation (OI) scheme for integrated parameters. • Model spectra are scaled and reshaped according to analysis (AN) integrated parameters of the subsystems. Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

19. ASAR assimilation impact on significant wave height according to buoy data (1-30 April 2005) Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

20. ASAR assimilation impact on peak wave period according to buoy data (1-30 April 2005) Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

21. ASAR assimilation impact on wave spectrum according to buoy data around Hawaiiin terms of equivalent 2-s sig. wave height(1-30 April 2005) most of wave energy Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

22. ECMWF Operational Assimilation of ENVISAT ASAR (Level 1b) • Until 31 January 2006, operational ECMWF wave model assimilates: • ENVISAT altimeter (RA-2) significant wave heights. • ERS-2 SAR wave spectra. • To be added on 1 February 2006: • ENVISAT ASAR wave spectra. • Jason altimeter significant wave height. • To be removed on 1 February 2006: • ERS-2 SAR spectra. Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

23. Verification of analysis wave heights against buoy observations5 April – 7 May 2005 Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

24. Conclusions (1) • Quality of ASAR Wave Mode Level 1b Product: • Inverted product agrees well with WAM model. • PF-ASAR Ver. 3.07 (May 2004) has positive impact. • Impact of model change of unresolved bathymetry (March 2004) is not clear. • Model change of improved dissipation (April 2005) has positive impact. Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

25. Conclusions (2) • Quality of ASAR Wave Mode Level 2 Product: • Bulk agrees well with WAM model (in terms of sig. wave height and mean period). • Spectral shape does not agree so well. • PF-ASAR Ver. 3.07 (May 2004) has no clear impact. • Positive impact after March-May 2004 may be due to model change (unresolved bath.) or PF-ASAR V3.07. • Model change of improved dissipation (April 2005) has positive impact. Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

26. Conclusions (3) • Data assimilation of ASAR Wave Mode Level 1b Product in ECMWF wave model: • Minor but positive impact. • ENVISAT ASAR Level 1b will be assimilated in ECMWF wave model operationally starting from 1 February 2006. Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006

27. QUESTIONS PLEASE Abdalla et al., SeaSAR 2006, ESA-ESRIN, 23 Jan. 2006