Xiaochun Wang Influence of Stratification on Semidiurnal Tides in Monterey Bay, California& Coastal Barotropic Tide SolutionsContributions from: JPL Yi Chao OSU C.K. Shum, Yuchan Yi UCLA Changming Dong, James McWillams NPS Leslie Rosenfeld, Jeffery Paduan NAO Koji Matsumoto, Tadahiro Sato Newcastle Xiaoli Deng; Hong Kong PolyTech Baki Iz

OSTST 2006 a ba: Jet Propulsion Lab/California Institute of Technologyb: Raytheon, ITSS . Validation of tidal solution . Influence of stratification

Comparison with TOPEX Barotropic Tide Away from the coastRoot of Summed Square 3.45cm

Baroclinic Tides Derived from Altimetry and ROMSSatellite Sample # Mean Amp Std Amp Corr (Amp) Corr (Pha) TOPEX 1013 0.52 0.30 0.195 0.103T/P-Tandem 1070 0.76 0.41 0.009 0.072 GFO 1855 0.81 0.46 0.101 0.087 ROMS 1013 0.25 0.15 1.000 1.000Significant at 99% level by Monte Carlo simulation.cmcm* Cycles used, TOPEX: 4-364, Tandem: 369-479, GFO: 37-168 Envisat: ~250 data points.

Baroclinic Tides Derived from Altimetry TOPEX T/P-Tandem GFOTOPEX 1.0 0.124 0.351 T/P-Tandem 84.3% 1.0 0.298GFO 99.2% 99.5% 1.0 TOPEX T/P-Tandem GFOTOPEX 1.0 0.157 0.206 T/P-Tandem 90.3% 1.0 0.079GFO 99.6% 85.1% 1.0 Correlation coefficients and their significant level, 99% highlighted. Amplitude Phase

Surface Tidal Currents with Different StratificationExperiment 1: Levitus climatology + Hourly forcing Experiment 2 1-year spin-up run from Levitus climatology + Hourly forcing Experiment 3 Data-assimilated initial condition of August 2003 + Hourly forcing Experiment 4 Data-assimilated initial condition of Aug. 2003 + Monthly forcing Tidal Current Improved

Barotropic and Surface Baroclinic Tidal CurrentsBarotropic Tidal Current Surface Baroclinic Tidal Current Both barotropic and baroclinic tidal current are changed with stratification

Subtle Stratification Change can make a difference.*Barolinic tidal forcing term, Baines (1982) F(N**2, Grad. h, Ub)

Comparison of 8 Short Period Tides Empirical Solutions and FES 2004 Tide Model TOPEX+JASON Along-track Solution FES 04: 2.4 cm RMSTOPEX+Tandem Mission Crossovers FES 04: 3.5 cm RMS (squares)OSTST, Hobart, 3/07; OSU, JPL, NAO, Newcastle U., HK Polytech U.

TOPEX-only Along-track Solution FES 04: 2.6 cm RMSTOPEX+JASON Along-track Solution FES 04: 2.4 cm RMSComparison of 8 Short Period Tides Empirical Solutions and FES 2004 Tide Model (Alaska)OSTST, Hobart, 3/07; OSU, JPL, NAO, Newcastle U., HK Polytech U.

TidesTOPEX onlyTOPEX+JASONChange/AmplitudeM2K1O1S2N2P11.011.160.831.610.570.540.951.160.711.530.520.53-0.1% of 49 cm 0.0 % of 26 cm-0.7 % of 16 cm-0.5 % of 16 cm-0.5 % of 10 cm-0.1 % of 9 cmTotal2.6 cm2.4 cm-0.2% of 61 cm

Comparison of 8 Short Period Tides Empirical Solutions and FES 2004 Tide Model Multi-satellite Empirical Solution FES 04: 2.2 cm RMS along T/P tracks (T/P, Tandem, Jason, GFO, ENIVSAT) 3.3 cm RMS at crossovers 4.6 cm RMS at all grid pointsOSTST, Hobart, 3/07; OSU, JPL, NAO, Newcastle U., HK Polytech U.TOPEX: 2.6, TOPEX+Jason: 2.4 (Along T/P tracks)

Comparison of 8 Short Period Tides Empirical Solutions and FES 2004 Tide ModelOSTST, Hobart, 3/07; OSU, JPL, NAO, Newcastle U., HK Polytech U.Patagonia ShelfEast China Sea

Changes of RMS Difference due to increased TOPEX data span in the coastal study regions Alaska area: 2.6 cm to 2.4 cm (61 cm) California (MB): 1.6 cm to 1.5 cm (44 cm) Patagonia: 5.2 cm to 5.0 cm (66 cm) East China Sea: 9.3 cm to 9.2 cm (56 cm) NW Atlantic: 3.1 cm to 2.9 cm (41 cm)

Preliminary Conclusions Improved agreements with FES 2004 by increasing TOPEX data span (O1, K1, P1, S2, and N2 tides) Multi-satellite solution agrees with FES 2004 model better than Dual-satellite solution of TOPEX+JASON along T/P and JASON tracksComparison of 8 Short Period TidesEmpirical Solutions and FES 2004 Tide ModelOSTST, Hobart, 3/07; OSU, JPL, NAO, Newcastle U., HK Polytech U.

Summary

Barotropic and baroclinic tidal solutions from altimeter observations prove to be useful to validate regional OGCMs. Marginal improvement observed in using multi-satellite altimetry in study regions.

Baroclinic tide amplitude and phase generated by model have significant correlation coefficients with TOPEX and GFO observations. Magnitude is smaller by a factor of 2-3.

Subtle changes in stratification can cause changes in tidal current in coast regions, which poses a challenge for tide-permitting forecasting systems.

Future work: Regional model for Alaska, Improve tidal solutions

Three Level Nested ROMS 3-Level Nested Model Grid Size Time Step Res. L0: 85*170*32 900s 16.5km L1: 95*191*32 300s 5.3km L2: 83*179*32 100s 1.6km 16 Processors on SGI Altix 3000 1 hour integration takes 1min cpu time.Los AngelesSan FranciscoMonterey BayMonterey Bay

Baroclinic Tide around Mendocino Escarpment Baroclinic Tide EnergyEnergy Flux J/m^2Consistent with observation (Althaus et al. 2003) J/m*m

Comparison with Tide Gauges Monterey Domain3 Gauges US SW Coast Domain 10 GaugesRSS 3.51cmRSS 5.41cmAlong the coast

Barotropic Tidal Current ComparisonROMS vs. TPXO.6RMS/Mean (%)RMS/Mean (%)ROMS vs. ADCIRC

Baroclinic Tide Theory Generation Energetics Baroclinic Tide Forcing Subscript i : Baroclinic Subscript 1: BarotropicG: ForcingD: Dissipation E: Baroclinic tide energy CgE: Baroclinic tide energy flux Baines (1982), Gill(1982)Stratification, Bathymetry, Barotropic tide flux

The altimetry data from multiple satellites (Topex/Poseidon - TOPEX data used, T/P Tandem mission, GFO) were used to derive internal tide signal in the U.S. west coast along central and northern California region. The method used is to do a 300km low-pass filtering along each track to remove the barotropic tide signal and then derive the amplitude and phase of internal tides. For T/P, the data for cycles 4-364 were used. For T/P tandem, the data for cycles 369-479 were used. For GFO data the cycles from 37 to 168 were used. Shown in left is the result from TOPEX only.

ROMS model has a horizontal resolution of around 16km and 32 levels in vertical direction which follow the bottom topography.The ROMS run starts from an averaged condition of Aug. 2003. The model is integrated for one month and forced by barotropic tide transport and sea surface height along open boundaries in north, west and south direction. The tide boundary condition is from TPXO6.0 of OSU. The hourly model output is used to derive the internal tide signal. For model output, the internal tide is derived from the baroclinic pressure of the top level of the model. Another method which uses a run with homogeneous density to derive the barotropic tide signal and then the sea surface height difference between this run and a run with stratification is used to derive the internal tide signal. Two methods give essentially the same results. Thus the results using baroclinic pressure from model top level are presented.

The topographic feature of the region is Mendocino Escarpment along 40N, which generates strong internal tides and the generated internal tides can propagate northward and southward.There are some internal tides generated by isolated topographic features in the southern part of the model domain.

Internal tide amplitude derived from Topex data shows increased internal tide amplitudearound 125W and 40N. The amplitude from Topex, T/P Tandem mission and GFO is generally larger than that from the model by a factor of 2-3 as indicated by the mean of the amplitudes(Table) .

The comparison between altimetry and ROMS (correlation coefficient of amplitude and phase for all the available data points in the model domain) is very encouraging since the correlation coefficient between T/P and ROMS, GFO and ROMS are larger than 0.08. Monte Carlo simulation indicates that the correlation coefficient larger than 0.08 is significant at 99% level.

At 1-Hz GDR sample points, along-track orthotide solutions for 8 major short period and 3 long period tides were made using TOPEX and JASON altimeter SSH data. Plotted tracks show, for a test area near Alaska, the difference (H1 and H2 amplitudes combined) for 8 short period tides between this empirical solution and the FES 2004 tide model, which is 2.4 cm RMS for all along-track data points.The square symbols added to T/P tracks represent the crossover points of TOPEX and Tandem Mission, for which the similar empirical solutions have a 3.5cm RMS difference from the FES 2004 tide model.A conclusion: The empirical solutions for both types of dual-satellite data show consistently that largest model discrepancies are found in coastal seas.By adding about 3 year long JASON altimeter data to the orthotide solution along the TOPEX tracks, the short period tidal solutions get closer to the FES 2004 model from 2.6cm to 2.4cm RMS in the Alaskan test area. The table of breakdown by tidal constituents shows that O1, S2, and N2 tides get better improvements by increasing the effective time span of altimeter data used.Although not included here, the empirical solutions at the crossover points of TOPEX and Tandem Mission show similar improvements by adding 3 year long Tandem Mission data to TOPEX data (9 year long).The same orthotide solutions were made on a grid of x degrees using altimeter data of multiple missions: TOPEX, Tandem Mission, JASON, GFO and ENVISAT.The multi-satellite empirical solution, when evaluated against FES 2004 model along T/P tracks, has a 2.2 cm RMS difference lower than 2.4 cm RMS of the corresponding TOPEX+JASON empirical solution for the test area near Alaska. However, the agreement of multi-satellite solution with FES 2004 model is not as good at the grid points away from the T/P and Tandem Mission tracks.

Shown here are similar short period tide differences of multi-satellite empirical solutions on a quarter-degree grid from the FES 2004 model in two other test areas.In all test areas, the multi-satellite empirical solution consistently has better agreements with the FES 2004 model along the T/P and Tandem Mission tracks compared with the dual-mission solutions of TOPEX+JASON or TOPEX+Tandem Mission.For all of test areas, orthotide Empirical Solution gets closer to FES 2004 Model by adding JASON or Tandem Mission data to TOPEX, effectively increasing the TOPEX data span, especially for O1, K1, P1, S2, and N2 tides.

Three stations: Moss Landing, Santa Cruz, Monterey Bay