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Modeling Focus (2006): Mixing Segment; Restratification

Modeling Focus (2006): Mixing Segment; Restratification. Mixing, day ~214; Restratification, ~217. Mixing Segment Evolution of mean profiles of N 2 , M 2. Restratification Segment N 2 , M 2.

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Modeling Focus (2006): Mixing Segment; Restratification

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  1. Modeling Focus (2006): Mixing Segment; Restratification

  2. Mixing, day ~214; Restratification, ~217

  3. Mixing SegmentEvolution of mean profiles of N2, M2

  4. Restratification Segment N2, M2

  5. Long integration time: 10 days covering both mixing and restratification segments.Low resolution: 3m X 3m X 2.8m; 1s timestep Smallest domains: 144m X 144m X 57m Largest domains: 1152m X 1152m X 57m Horizontally periodic in departure from background zonal gradients in T & S ; r & pInitial Conditions: 20m mixed layer over stratification ~ 9.0x10-2 C/m & 1.2x10-2 psu/m or N2=2.5x10-4 s-2 & vertical spice stratification 1.2x10-4 s-2Zonal Gradients: dr/dx = + 6.25x10-5 kg/m4 from -1.17x10-4 C/m & 4.75x10-5 C/m or M2=-5.9x10-7s-2 & horizontal spice stratification 1.1x10-7 s-2Surface Forcing‘COAMPS/WW3’ Case: Surface Stress + Stokes drift US from COAMPS & WW3 ‘Obs./WW3’ Case: Surface Stress + Stokes drift US+ Obs. Heat Fluxes, Radiation LES modeling cases

  6. COAMPS/WW3 model case SST, mixing phase ‘Large’ Domain, 576m x 576m U10

  7. COAMPS/WW3 model case SST, mixing phase ‘Largest’ Domain, 1152m x 1152m U10

  8. Near-Surface Langmuir Circulation W(cm/s) ‘Largest’ Domain, 1152m x 1152m U10

  9. Brief Summary of Some Results: • Mean observed & LES modeled mixed layer Vertical TKE levels are consistent with Langmuir Turbulence. ‘Ekman Convection’ does not increase mean VKE. • Mixed layer deepens rapidly by ‘Ekman Adjustment’, not ‘Ekman Convection’, independent of model domain scale & mixed layer TKE variability (i.e. turning Stokes drift off changes TKE but not mixed layer deepening). • Rapid Observed restratification after wind falls is similar to LES with surface heat flux forcing, but differs in some details. • Comparing LES with KPP: Horizontal vorticity (& P.V.) very different.

  10. Horizontal Fluxes Example with No Mean Lateral Gradients: Entraining Mixed Layer, u*=1 cm/s, Mature Seas

  11. COAMPS/WW3 Case (‘Large’ Domain)

  12. Sharp mini-fronts: Local downwelling, increased VKE

  13. Lagrangian float VKE variability: Is it something, or is it just statistical? Potential Model-Data Comparisons Surface signature of ~300m long surface convergence observed at FLIP, later and to South during AESOP’06 by J M Smith.

  14. Summary: Modeled lateral fluxes in upper ocean during wind-driven mixing are significant compared to K~1-10m/s significant compared to along & cross-front dispersion by mean U,VLateral fluxes increase with LES domain size… presumably corresponds to resolution dependence of subgrid flux.Turning off surface wave Stokes drift greatly reduces LES horizontal fluxes.

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