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Simulated Sea Surface Salinity Variability in the Tropical Pacific Xiaochun Wang Yi Chao JPL/Caltech Terrain-Following Ocean Models User Workshop Seattle,

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Presentation on theme: "Simulated Sea Surface Salinity Variability in the Tropical Pacific Xiaochun Wang Yi Chao JPL/Caltech Terrain-Following Ocean Models User Workshop Seattle,"— Presentation transcript:

1 Simulated Sea Surface Salinity Variability in the Tropical Pacific Xiaochun Wang Yi Chao JPL/Caltech Terrain-Following Ocean Models User Workshop Seattle, Aug. 4-6 Acknowledgement: Discussions with J. McWilliams, P. Marchesiello, A. Shchepetkin, T. Song, Y. Golubev about the use of ROMS model. Computations were performed on computers of JPL and NASA Ames Research Center.

2 Scientific Issues What is the Sea Surface Salinity (SSS) structure associated with the ENSO phenomenon? What are the detailed features of SSS seasonal cycle? Are there any salinity signatures associated with the Tropical Instability Waves (TIWs)?

3 Motivation The effect of salinity on dynamics is gradually realized, e.g. barrier layer, influence on SSH, … However, salinity has very sparse observation. Aquarius mission, measure monthly SSS with accuracy of 0.2 psu with horizontal resolution of 100km

4 Pacific ROMS (Regional Ocean Modeling System) Horizontal resolution, 50km, 45S-65N, 99E-70W 20 S-coordinate levels KPP scheme Open boundary condition 1990-2001 NCEP-NCAR Daily Forcing (Wind stress, heatflux, precipitation and evaporation) 5-day (pentad) average

5 Validation of Model Simulation TAO Data 5-day 99% Sig.

6 SSS Change on InterannualTimescale 1-yr lowpassed Freshening during ENSO

7 Spatial Pattern Associated with ENSO EOF Analysis Consistent with Ob. Variance (24.9%)

8 Seasonal Cycle of SSS EOF Analysis Variance (66.0%) ITCZ Annual Mean

9 SSS Features Associated with TIWs SSS SST and Current 50day Highpassed

10 Westward Propagation Seasonal Change Intreannual Change 50day Highpassed SSS Features of TIWs

11 Spatial Features of TIWs.Fresh.Warm.Upward.Southward.Eastward

12 TIWs SSS Variability is along EQ

13 Why TIWs SSS Variability is along EQ? Meridional Advection !

14 SSS Variability on Different Timescales Total Interannual Seasonal Intraseasonal (<50day)

15 Summary The western tropical Pacific is a region of large variability on different timescales, interannual, seasonal, and intraseasonal. Though ENSO events show up as a freshening of the whole equatorial Pacific, the eastern equatorial Pacific is not a center of SSS variability on interannual timescale. On timescale shorter than 50days, besides the variability center in the western tropical Pacific, there is a variability center along the equator in the eastern equatorial Pacific associated with the TIWs.


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