1. Filling the Gap: The Structure of Near Coastal Winds Jeroen Molemaker, Francois Colas and Xavier Capet University of California Los Angeles

2. Forcing our ocean models: wind Global atmospheric model (reanalysis)‏ Observed winds (scatterometer, climatology, stations)‏ Regional atmospheric model (early stage of coupling)‏

3. Wind forcing Global atmospheric models are too course to resolve any structure near the coast. Coupling with regional atmospheric models may be the future but is there an intermediate option?

4. quikscat leaves an 25-50 km gap

5. Why should we care? Wind stress curl determines upwelling. Small changes in curl result ‘big’ changes in upwelling. (Capet, 2004) and, again, this talk.

6. Near-shore wind drop-off Absent in coarse reanalysis wind products Still questionable in (uncoupled) atmospheric regional models

7. Near-shore wind drop-off Land-sea changes in surface drag and boundary layer. In-situ observations : Very scarce, but give indication of a drop-off Point Reyes Summer:  /4 within ~ 25km Winter:  /2 within ~ 25km Dever et al. (2006), Dorman et al. (2006)‏

8. A relation between wind and SST gradients (Chelton using QSCAT) (Chelton et al. 2001, 2007)‏

9. Wind / SST gradient Empirical Relation

10. Wind / SST Empirical Relation implementation in ROMS “online”: Correct Wind stress during simulation using actual computed SST’s. Application: wind feedback on eddies and fronts. “offline”: Correct QuikCOW wind stress climatology before using in ROMS Objective : impact on quasi-equilibrium climatological solutions. Try to fill wind ‘gap’ using this relation.

11. Online wind/sst coupling

12. Test wind/SST relation at climatologic time scales Curl(  ) Div (  ) Crosswind SST gradientDownwind SST gradient

13. Test wind/SST relation at climatologic time scales -- crosswind grad(SST) -- curl (t) Along-shore  Surprisingly good already!!

14. So what is missing? Land-sea changes in surface drag and boundary layer. Summer:  /4 within ~ 25km Winter:  /2 within ~ 25km Dever et al. (2006), Dorman et al. (2006)‏ Orographic effects

15. Orography: zeroth order approach Reduce near coastal wind by 50%  corr =  [1- 0.5exp(-  D) ] D = distance to coast  = 1/(20 km)

16. Coast wind reduction

17. Wind / SST Empirical Relation in ROMS 2 ROMS configurations – climatological conditions Peru/Chile (4 km)‏ (VOCALS region)‏ California (5 km)‏ (Capet et al. 2008)‏ (Colas et al. 2008)‏

18. Near-shore SST sensitivity (CCS)‏ Difference with Pathfinder Climatology quikCOW quikCOW plus ‘Orography’

19. Alongshore current difference

20. Average structure of undercurrent quikCOW quikCOW plus ‘Orography’

21. Lagrangian estimate of undercurrent flow Garfield et al. (2001)

22. Surface Eddy Kinetic Energy original quikCOW winds corrected windsaltimetry (DUACS)‏ [cm 2.s -2 ]

23. Along-shore averaged EKE -- quikCOW -- With ‘Orography -- Altimetry

24. original QSCAT windscorrected winds Near-shore SST sensitivity (PCS)‏ Difference

25. Why did we care: Oceanic heat balance in the PCS - role of eddies Systematic errors in CGCMs in the South East Pacific: Difficult to reproduce the stratus cloud deck and to simulate the upwelling and its effects. Role of eddies in the transport of heat (VOCALS project). (Large and Danabasoglu, 2006)‏ SST warm bias in CGCM Potential upscaling effects from EBUS

26. - Wind/SST empirical coupling in regional model: near-shore wind drop- off, significant changes on upwelling structure and consequent related eddy activity (heat balance, offshore transport). - Wind/SST relation and near-shore structure need to be tested using an coupled atmospheric model - Possible upscaling effects at regional scale and even larger scale are important.