Lagrangian Statistics in Nonhydrostatic and QG turbulence Baylor Fox-Kemper (Brown)

Transcription

1 Lagrangian Statistics in Nonhydrostatic and QG turbulence Baylor Fox-Kemper (Brown) LAPCOD, Schoodic Pt., ME 7/28/15 Sponsor: GoMRI/CARTHE P. E. Hamlington, L. P. Van Roekel, BFK, K. Julien, and G. P. Chini. Langmuirsubmesoscale interactions: Descriptive analysis of multiscale frontal spin-down simulations. Journal of Physical Oceanography, 44(9): , September movie credit: P. Hamlington

2 S. Bachman, BFK, and F. O. Bryan. A tracer-based inversion method for diagnosing eddy-induced diffusivity and advection. Ocean Modelling, 86:1-14, February (Sub)Mesoscale Eddy Advective & Diffusive Transport Flux-Gradient (Anisotropic) Symmetric=Diff. Antisymmetric=Adv. BFK, R. Lumpkin, and F. O. Bryan. Lateral transport in the ocean interior. In G. Siedler, S. M. Griffies, J. Gould, and J. A. Church, editors, Ocean Circulation and Climate: A 21st century perspective, volume 103 of International Geophysics Series, chapter 8, pages Academic Press (Elsevier Online), S. Bachman and BFK. Eddy parameterization challenge suite. I: Eady spindown. Ocean Modelling, 64:12-28, 2013

3 Way to go Grads! Mesoscale eddies follow the Obukhov- Corrsin spectral slope! K. McCaffrey, BFK, and G. Forget. Estimates of ocean macro-turbulence: Structure function and spectral slope from Argo profiling floats. Journal of Physical Oceanography, 45(7): , July 2015

4 Oversimplify! 3d Isotropic, Homogeneous Turbulence: Forward KE Cascade k -5/3 Forward KE Inertial Range 2d/QG Isotropic, Homogeneous Turbulence: Inverse KE Cascade Inverse KE Inertial Range

5 shown in Figs. 4a and 4b is characterist Movie:The P. Hamlington turbulence. greatest changes to sm Model #1: Multiscale LES of lence in the Stokes simulations occur n Langmuir & Submeso Turbulence perature gradients where strong vertica observed. Figure 4b shows such a region intense negative velocity is approximate surface Langmuir Turb. a locally steep temperature front. By c shows that there are relatively large reg magnitude in the no-stokes simulation, k-2 results for the full domains shown in Figs existence of these regions indicates t turbulence is suppressed by submesosc though the mechanism of this suppressio Wind, understood. It should be noted that even Waves case possesses coherent small-scale struc horizontal vorticity, although these struc acteristic of shear turbulence in the no-st structures in the Stokes case are ch Langmuir turbulence. The small-scale structure of w in both s can be examined more directly u dimensional vertical velocity spectra sh Domain size: 20km x 20km x -160m movie are credit: which given as functions of the ho FIG. 3. One-dimensional circularly integrated spectra for velocgrid points: 4096 x 4096 x 128 P. Hamlington numbers kx and ky. Near the surface ities u, y, and wresolution: and temperature u in the Stokes (solid lines) and 5m x 5m x -1.25m no-stokes (dashed lines) simulations near 12 days. Spectra are stantially greater small-scale energy P. E. Hamlington, L. P. Van Roekel, BFK, K. Julien, and G. P. Chini. Langmuir-submesoscale interactions: Descriptive analysis of multiscale fron shown at depths (a) z m and (b) z m and are norsimulation than in the no-stokes down simulations. Journal of Physical Oceanography,Stokes 44(9): , September 2014.

6 Initially every surface node has 1 drifter, so there are drifters in the picture > 18 4 y (km) After 40 Min 2 x (km) 3 4 0

7 Initially every surface node has 1 drifter, so there are drifters in the picture > y (km) After 80 Min x (km) 0

8 Model #2: Multiscale QG Simulation of Submesoscale & Mesoscale Turbulence Domain: 512km x 512km x -500m Grid points: 512 x 512 x 3 Resolution: 1km x 1km x exact k -5/3 Inverse KE Inertial Range k -3 movie credit: J. Callies J. Callies, G. Flierl, R. Ferrari, and BFK. The role of mixed layer instabilities in submesoscale turbulence. Journal of Fluid Mechanics, Submitted.

9 KE Flux Estimates Simulated Drifters (sign indefinite) Also from Mann et al But, what happens if we do this in these runs?

10 KE Fluxes Simulated Drifters in SM/Lang. Langmuir Turb. Range. Doesn t predict any separation dependence A pretty good fit if: but inverse Langmuir cascade?

11 KE Fluxes Simulated Drifters in QG/SQG Inverse KE Inertial Range

12 Conclusions Upper Ocean Turbulence, Fronts, & Instabilites are important, and are beautiful to contemplate Interesting transition in physics, as nonhydro. & ageostrophic effects begin to dominate In realistic upper ocean Langmuir to mesoscale turbulence simulations, drifter-like energy flux diagnostics (based on surface velocities) from 3d Kolmogorov scalings give order of magnitude agreement with each other. However, incongruities between the estimates, such as predicting the wrong scales over which inertial ranges occur, or forward cascades when inverse cascades are present, mean that these methods are not appropriate without modification. All papers at: fox-kemper.com/pubs

13 Fluxing Across Fronts Smith, K., P. Hamlington, and B. Fox-Kemper. Effects of submesoscale turbulence on tracer evolution in the oceanic mixed layer. Submitted 2015.