GTP: Geophysical Turbulence Program and TNT: Turbulence Numerics Team IMAGe Advisory board Boulder, January 26, 2009 1 Geophysical Turbulence Program GTP has been in existence almost since the beginning of NCAR (Deardorff, Gilman, Herring, Leith, Lilly, Lorenz, McWilliams, Orszag, Patterson, Thompson, ) History: see Herring, in IUTAM Symposium, Kerr & Kimura Eds, Kluwer (2000) 40+ members across all divisions and labs at NCAR + a few external universities (CU, Dartmouth, LANL, Nagoya, Penn State, UCLA, Warwick)

GTP, @ $50k, is ~ 10% of the GTP+TNT combined budgets Imperative: cross-cutting research with outreach Support research on turbulent flows in a variety of contexts, with focused topics drawing on GTP seed funds Short-term (3-day) visitors, with a ``monthly seminar program Long-term visitors, for one week [to one year, very rarely possible] Workshops [and schools, 2 in 20 years] For the last two years: small partial support for graduate students URGENCY: TO INVOLVE THE YOUNGER GENERATION

2 Sullivan (ESSL/MMM - GTP): Boundary layers ``The atmospheric and oceanic boundary layers may be the most crucial ingredients in hurricane dynamics despite their small vertical extent (K. Emanuel, 2004) SST . .. Cold water hurricane wake generated by ocean turbulence and surface wave effects . .

Large eddy simulations and .. modeling of turbulent flows Storm track and of boundary layers in complex geophysical flows, High wind atmospheric PBL 25m/s with multi-scale dynamics and physical processes. Transition wave - turbulence Breaking waves, spray, bubbles, turbulence? 3 ribbia (ESSL-CGD & GTP), with Jim McWilliams (UCLA-GTP)

Pathway to dissipation in the atmosphere and ocean Thermal / mechanical driving on planetary scale Thin instabilities (baroclinic, frontal) drive inertial cascades to non-rotational scales Further instabilities (K-H, convective) needed to get to 3D isotropic turbulence and dissipation, and transport processes No complete GFD simulation to date. It must span a 2D range from 106 m to 10-100m ce), waves and anisotropy (rotation and/or stratification and/or mag and/or 4 bottom GTP possible mission statement The Geophysical Turbulence Program at NCAR investigates nonlinear multi-scale eddy-wave interactions for a wide range of geophysical and astrophysical flows. It also develops, analyzes and validates analytical and phenomenological models, numerical methods and experiments as

tools for UCAR and for the university community, here and abroad. Retreat + meeting of GTP to be organized in 2009 (Joe Tribbia) To be followed by a meeting of a small advisory board (as per the request of the NCAR review panel many years ago ) 5 GTP seminars in 2007 and/or 2008 J. Baerenzung (NCAR): Spectral modeling of utrbulent fluids G. Boffetta (LANL): Two-dimensional turbulence. C. Bustamante (U. Warwick): Singularities of the Euler equations. P. Hamlington (U. Mich.:, Reynolds stress anisotropy and vorticity alignment. S. Heinz (U. Wyoming): Unified stochastic and deterministic turbulence models (07). J. Liu (CSU): Characteristic methods for fluid transport problems. D. Stanescu (U. Wyoming): Discontinuous Galerkin methods (07). A. Tuck (NOAA): A molecular view of vorticity and turbulence. V. Uritsky (U. Calgary): Self-organized criticality. MHD (W-C Mller, W-H Matthaeus, )

6 GTP visitors and graduate students - 07 &/or 08 M-E Brachet, ENS-Paris: codes with symmetries in MHD, RK4 and Euler flow with helicity. J.F. Cossette (grad. student, U. Montreal, with Piotr Smolarkiewicz): Semi-Lagrangian schemes. M. Damron (grad. student, U. Arizona, with Larry Winter): a non-Markovian model of rill erosion. J. Finnigan (Commonwealth Scient.): Canopy turbulence in roughness sub-layers D. Jarecka (grad. student, U. Warsaw, with Wojciech Grabowski): Impact of entrainment and mixing on cloud dynamics and microphysics. H. Jonker, U. Delft: A refined view of vertical transport by cumulus convection. P. Ortiz, U. Granada: Coupled dynamics of boundary layers & evolutionary landforms like dunes. Z. Piotrowski, U. Warsaw: Numerical realizability of thermal convection. L-P Wang, U. Delaware: Turbulent collision-coalescence of cloud droplets and impact on warm rain initiation. 7 Collision-coalescence processes in cloud microphysics Wang, Franklin, Ayama & Grabowski - ESSL/MMM-GTP PDF of angle of approach of colliding droplets: dominance of

inward relative motion due to turbulence Solid line: model with turbulence black dots: Direct Numerical Simulation (DNS) 8 GTP/TNT workshops 08 Theme of year: 3-wks Summer School & 3 wkshps (K. Julien @CU, CISL-EOL-ESSL-RAL) * Theory and modeling of Geophysical Turbulence: LANL (B. Wingate) + Wisconsin (L. Smith) * Petascale computing for Geophysical Turbulence: CORA (J. Werne) + UCLA (B. Stevens) * Observations and sensors: RAL (L. Cornman) + EOL (S. Oncley) + ESSL (R. Lenschow) (J. Fernando [AZ] in charge of the Observation week of the summer school) No magnetic field in TOY-08 2009?: Turbulent mixing in the upper ocean & boundary layers (W. Large, ESSL-CGD) 2010: Rotating stratified flows (V. Zeitlin, Paris et al.) Past workshops: Turbulence and Dynamos at Petaspeed (2007) Turbulence and Scalar Transport in Roughness Sub-layers (2006)

Modeling MHD turbulence with applications to planetary and stellar dynamos (2006) Theme of the Year (TOY-06) on Multi-scale modeling (one workshop sponsored) Coherent Structures in the Atmosphere and Ocean (2005) Atmospheric Turbulence and Mesoscale Meteorology (2005) Cumulus Parameterization in the Context of Turbulence Studies (2004) 9 A sample of GTP-supported research [1] G. Branstator (ESSL-CGD) & J. Berner (now in MMM): distinct signatures of nonlinearity in climate dynamics W. Grabowski (ESSL-MMM): Parameterization of small-scale and micro-scale processes in models resolving larger scales J. Herring (ESSL-MMM): Stratified turbulence R. Lenschow (ESSL-MMM): Analysis of C-HATS experiment (Horizontal Array Turbulence Studies, + Oceans, Canopies, Anisotropy) C-H Moeng (ESSL-MMM) with J. McWilliams (UCLA), R. Rotunno (MMM), P. Sullivan (MMM) & J. Weil (CIRES/CU) : Evaluation of two-dimensional Planetary Boundary Layer (PBL) models 10 using Large Eddy Simulations (LES)

Passive versus active scalar in the dry PBL using LES in a large domain 10002X128 or 502km X 6km Peter Sullivan, ESSL-MMM -& GTP: (comparable to a field campaign) Passive scalar is at large scales Dynamically active scalar is at the velocity scale (depth of PBL) 11 A sample of GTP-supported research [2] M. Rast (CU): Convection + ionisation in the solar convection zone P. Sullivan (ESSL-MMM) et al.: wind-wave interactions; J. Tribbia (ESSL-CGD): Multi-scale and climate New! J. Berner (ESSL-MMM) et al.: stochastic parametrization for numerical weather

prediction (NWP) with flow-dependent formulation of unresolved processes 12 Stochastic parameterization of spectral backscatter for NWP and climate model-error Stream function perturbations with a prescribed kinetic energy spectrum: J. Berner, A. Fournier, S-Y. Ha, J. Hacker & C. Snyder Successfully applied to probabilistic NWP (ECMWF pseudo-spectral model) by Shutts (2005), and Berner et al. (2009). Ongoing: Implementation into WRF limited-area ensemble model using 2D planar Fourier analysis. Preliminary Result: the Brier score of u is improved (shown is score for events 0 < u < (p), where (p) is

climatological standard deviation at 13 pressure p), but more samples are needed. Action item for GTP Commonality of issues in fundamental multi-scale dynamics for the Earths atmosphere and ocean, and for solar and solarterrestrial physics Request for a quadrupling of the funds (50k Create a GTP Post-doctoral fellow Create a GTP Graduate student position Create a sabbatical GTP visitor 200k): The over-arching goal is to investigate and model turbulent 14 flows in weather, climate, solar physics and space weather Action item for GTP Commonality of issues in fundamental multi-scale dynamics for the Earths atmosphere and ocean, and for solar and solar-terrestrial physics

Request for a quadrupling of the funds (50k Create a GTP Post-doctoral fellow Create a GTP Graduate student position Create a sabbatical GTP visitor 200k): Decision making process: annual meeting of GTP members (+) The over-arching goal is to investigate and model turbulent flows in weather, climate, solar physics and space weather 15 And now, the Turbulence Numerics Team 16

Aim Fournier Project Sc. @1 FTE Pablo Mininni Scientist 1 @ 0.25 AP @ 0.6 QuickTime and a decompressor are needed to see this picture. ulien Baerenzung, ost-doc, 1 FTE (until June 2009) Duane Rosenberg, Software Eng. III, @ 1 FTE

TNT Team yesterday Core of 2.85 FTE Ed Lee, GRA, 0.5 FTE (until January 22, 2009) 17 + 1 GRA + 1 post-doc 40% deputy director of ESSL 75% at Buenos Aires Aim Fournier Project Sc. @1 FTE Pablo Mininni Scientist 1 @ 0.25 AP @ 0.6 QuickTime and a decompressor

are needed to see this picture. ulien Baerenzung, ost-doc (until June 2009) Duane Rosenberg, Software Eng. III, @ 1 FTE TNT Team yesterday Core of 2.85 FTE Ed Lee, GRA, 0.5 FTE (until January 22, 2009) 18 + 1 GRA + 1 post-doc At some point in June 2009:

Core of 1.85 FTE No GRA and no post-doc Two NSF gants submitted in 2008 19 Imperative tigate the basic properties of multi-scale f oit their commonality - multi-scale interactions, inear phenomena, geophysical turbulence, eddies and waves * Analyze data and implement a variety of turbulence mo the applications for the Earth and beyond: atmosphere, ocean, PBL, solar physics and space weathe at effect, develop, test and make available ols and data sets @ petascale and beyond

20 the ng, and also accessing, visualizing, analyzing & sharing Imperative tigate the basic properties of multi-scale f hest possible Reynolds number(s) oit their commonality - multi-scale interactions, inear phenomena, geophysical turbulence, eddies and waves * Analyze data and implement a variety of turbulence mo the applications for the Earth and beyond: atmosphere, ocean, PBL, solar physics and space weathe at effect, develop, test and make available ols and data sets @ petascale and beyond 21 the ng, and also accessing, visualizing, analyzing & sharing

Basic research by way of two large runs done at NCAR with GHOST on 15363 points, thanks to BTS and ASD allocations I. 2006: Magnetohydrodynamics (MHD), without rotation R ~ 1700 First evidence of a dual direct energy cascade: isotropic k-3/2 at large scale, anisotropic k-2 weak turbulence at small scale in the highest-ever Reynolds MHD run First numerical evidence of rolling up of vorticity & current sheets

Pablo Mininni et al. 22 Going beyond, with the help of symmetries First evidence of lack of universality in decaying MHD without a uniform magnetic field (20483 equiv. grid): Taylor-Green flow, 3 runs, 3 different energy spectra Collision of two current sheets (viz.: VAPOR, CISL) Ed Lee et al. Phys. Rev. E 2008/12 kaleidoscope 23 MAYTAG Going beyond, with the help of symmetries First evidence of lack of universality in decaying MHD without a uniform magnetic field (20483 equiv. grid):

Taylor-Green flow, 3 runs, 3 different energy spectra Ed Lee et al., in preparation Collision of two current sheets (viz.: VAPOR, CISL) Ed Lee et al. Phys. Rev. E 2008/12 kaleidoscope 24 MAYTAG Going beyond [2] Developing, testing, or using models for fluid & MHD turbulence: * Chollet-Lesieur model * Lagrangian averaged model (D. Holm, ) * Spectral model based on EDQNM (two-point turbulence closure) ^ with eddy viscosity incorporating helical terms ^ with eddy noise incorporating phase information

^ for any energy spectrum (Julien Baerenzung et al.) Applications to Navier-Stokes (including rotation) and MHD 25 Second large run at NCAR II. 2008: Rotation with helical R ~ 1100 , Ro = 0.05 forcing, without magnetic field GHO First evidence of a non-intermittent and non-Kolmogorovian direct energy cascade at low Rossby number, governed by the direct cascade of helicity (h+e=4), together with an inverse cascade of energy

First evidence of the persistence of strong cyclonic events in rotating turbulence in the presence of helicity, together with strongly turbulent columnar structures Pablo Mininni et al. rticity magnitude (zoom), above a threshold 26 Second large run at NCAR II. In 2009: * Analysis and modeling of the large run with rotation and helical forcing R ~ 1100 , Ro = 0.05

Parametric study using the model TBD Thanks to a special CISL 5 mo. post-doc allocation for JB 27 r look of vorticity magnitude, above a threshold: cohabitati Going beyond: Modeling of rotating flows Model: Eddy viscosity and eddy noise with variable index energy spectrum Tests helical

down to numbers on nonflows Rossby of 0.02 QuickTime and a decompressor are needed to see this picture. Taylor-Green flow Fig.: Build-up of anisotropy GHOST + X 28

Adaptive Mesh Refinement 2D-Navier-Stokes Aim Fournier et al., 2008 Decay for long times (incompressible) Formation of dipolar vortex structures Gain in the number of degrees of freedom (~ 4) with AMR, compared to an equivalent pseudo-spectral code (periodic boundary

conditions) GASPAR 29 Spectral AMR The need for accuracy in adaptive mesh refinement, when looking at max. norms (Fig.: current in 2D-MHD reconnection) Duane Rosenberg et al (2007) Also:

Development of optimized Schwarz preconditioning, in collaboration with Amik St 30 GASPAR Available TNT tools GASpAR: High-order adaptive Mesh Refinement code for turbulent flow, and a PDE framework for adaptive mesh solutions * Future: Boussinesq equations, 3D-MHD, Planetary Boundary Layer GHOST: Primary production pseudo-spectral code for turbulent flows Modular numerics and physics: 2D/ 3D; compressibility; (Hall)-MHD; rotation * Plans: * Stratification, and implementation of (several) LES * Upgrade for petascale and beyond (today: up to ~ 4000 proc.) ^^^^^^^^^^

Other code: MAYTAG: MAgnetohYdrodynamics TAylor-Green code with enforced symmetries leading to a gain of 32 in CPU / storage Code developed in F08 by M-E Brachet (ENS Paris) 31 Available high Reynolds number numerical data sets (runs performed at NCAR, NERSC and Pittsburgh) Navier-Stokes: ^ Taylor-Green (TG) flows, 20483 grids ^ ABC flows, 20483 grids Navier-Stokes with rotation: ABC, decay,15363 grid MHD: ^ 10243 forced dynamo runs; ^ 15363 grid, decaying flow; ^ 20483 equivalent grids with imposed TG symmetries Taylor Reynolds numbers of 1100 or above

32 New research directions ic research in rotating turbulent flows (in progres al simulations, phenomenological approach, and l modeling (with helicity and with eddy noise) atified turbulent flows (GHOST) /without rotation, boundaries, passive tracer; & numerical a l targeted applications to the stable planetary boundary laye er Sullivan, ESSL; & Rod Frechlich, RAL) ircraft safety (with Larry Cornman, RAL) tom topography using non-uniform mesh (GASPAR) 33 New needs: Action items for TNT 1- Basic research in rotating turbulent flows (in progress): Numerical

simulations, phenomenological approach, and spectral modeling 2 - Stratified turbulent flows (with/without rotation, boundaries, passive tracer; and numerical adaptivity). Potential targeted applications to the stable planetary boundary layer and to aircraft safety (with ESSl and RAL) 3 - Bottom topography, using mesh adaptivity A- Tools for the community (GASPAR, GHOST), going to petascale and beyond B- High-Reynolds number data sets for the community, and how to handle these data sets A- Sustain the TNT team at its present level B- Recruit in TNT a Scientist 1 or Scientist 2 34 in weather/climate turbulence and its modeling TNT collaborations at NCAR, past and present: Tom Bogdan (now at NOAA), Paul Charbonneau (now at Montreal), John Clyne (CISL), Larry Cornman (RAL), Rod Frehlich (RAL and CU), Jack Herring (emeritus, ESSL-M3), Han-Li Liu (ESSL-HAO), Alan Norton (CISL), Amik St Cyr (IMAGE-CISL),

Peter Sullivan (ESSL-MMM), Joe Tribbia (ESSL-CGD), TNT collaborations outside NCAR, past and present: A. Alexakis (Paris), F. Baer (U. Md), A. Bhattacharjee (UNH), M-E Brachet (Paris), B. Breech (U Del.), M. Bustamante (Dublin), V. Carbone (Calabria), C. Cartes (Santiago), S. Cowley (UCLA), P. Dmitruk (Buenos Aires), P. Fisher (Argonne), S. Galtier (Orsay), K. Germaschewski (UNH), J. Graham (Lindau), D. Holm (Imperial, LANL), G. Krstulovic (Paris), D. Lathrop (U. Md), W-H Matthaeus (Bartol), D. Montgomery (Dartmouth), C-S Ng (Alaska), J-F Pinton (Lyon), H. Politano (Nice), Y. Ponty (Nice), J. Toomre (CU), M. Rast (CU), R. Reddy (PSC), J. Riley (U. Washington), M. Taylor (Sandia), L. Turner (Cornell), V. Uristsky (Calgary), H. Wang (U. Md), 35 Publications with reviewers, 2007-2009

[1] Alexakis, A., P. D. Mininni, A. Pouquet, 2007: Turbulent cascades, transfer, and scale interactions in magnetohydrodynamics. New J. Phys., 9, 298, doi: 10.1088/1367-2630/9/8/298. Baerenzung, J., H. Politano, Y. Ponty, A. G. Pouquet, 2008: Spectral modeling of turbulent flows and the role of helicity. Phys. Rev. E, 77, 046303, doi: 10.1103/PhysRevE.77.0463033 J. Baerenzung, H. Politano, Y. Ponty and A. Pouquet,, `Spectral Modeling of Magnetohydrodynamic Turbulent Flows,' Phys. Rev. E 78, 026310 (2008). Carbone, V., A. G. Pouquet, 2008: An introduction to fluid and MHD turbulence for astrophysical flows: Theory, observational and numerical data and modeling. Invited set of Lectures EEC School on Astrophysical Plasmas, L Vlahos and P Cargill, Ed., Springer-Verlag, 69-131 Carlos Cartes, Miguel D. Bustamante, Annick Pouquet, Marc E. Brachet,Generalized Eulerian-Lagrangian description of Navier-Stokes and resistive MHD dynamics,'' Fluid Dyn. Res, 41, 011404 (2009). Clyne, J., P. Mininni, A. Norton, M. Rast, 2007: Interactive desktop analysis of high resolution simulations: Applications to turbulent plume dynamics and current sheet formation. New J. Phys., 9, 301, doi: 10.1088/1367-2630/9/8/301. Cowley, S., J.-F. Pinton, A. Pouquet, 2007: Focus on magnetohydrodynamics and the dynamo problem. New J. Phys., 9, E04, doi: 10.1088/1367-2630/9/8/E04 A. Fournier, D. Rosenberg and A. Pouquet, ``Dynamically adaptive spectral-element simulations of 2D incompressible Navier-Stokes vortex decays,'' to appear, GAFD, Special issue `` Vortex dynamics from quantum to geophysical scales,'

Guest Editors: C. Barenghi, D. Dritschel and A. Gilbert (2008). Graham Pietarila, J., D. D. Holm, P. Mininni, A. G. Pouquet, 2008: Three regularization models of the Navier-Stokes equations. Phys. Fluids, 20, 035107, doi: 10.1063/1.2880275. Graham Pietarila, J., D. Holm, P. Mininni, A. G. Pouquet, 2008: Highly turbulent solutions of the Lagrangian-averaged Navier-Stokes alpha model and their large-eddy-simulation potential. Phys. Rev. E, 75, 056310, doi: 10.1103/PhysRevE.76.056310. J. Pietarila Graham, P.D. Mininni, and A. Pouquet, The Lagrangian-averaged model for magnetohydrodynamic turbulence and the absence of bottleneck, Phys. Rev. E, to appear (2009). E. Lee, M.E. Brachet, A. Pouquet, P.D. Mininni and D. Rosenberg,``A paradigmatic flow for small-scale magnetohydrodynamics,' Phys. Rev. E 78, 066401 (2008). Matthaeus, W. H., A. G. Pouquet, P. Mininni, P. Dmitruk, B. Breech, 2008: Rapid directional alignment of velocity and magnetic field in magnetohydrodynamic turbulence. Physical Review Letters, 100, 085003, doi: 10.1103/PhysRevLett.100.085003.

36 [2] * P.D. Mininni, A. Alexakis and A. Pouquet, Scale interactions and scaling laws in rotating flows at moderate Rossby numbers

and large Reynolds numbers,'' Phys. Fluids 21, 015108 (2009). P.D. Mininni and A. Pouquet, ``Helicity cascades in rotating turbulence,'' to appear, Phys. Fluids (2009), arxiv:0809.0869. Mininni, P., A. Alexakis, A. G. Pouquet, 2008: Non-local interactions in hydrodynamic turbulence at high Reynolds numbers: The slow emergence of scaling laws. Phys. Rev. E, 77, 036306, doi: 10.1103/PhysRevE.77.036306. Mininni, P., A. G. Pouquet, 2008: Energy spectra stemming from interactions of Alfven waves and turbulent eddies. Physical Review Letters, 99, 254502, doi: 10.1103/PhysRevLett.99.254502. Mininni, P. D., D. C. Montgomery, L. Turner, 2007: Hydrodynamic and magnetohydrodynamic computations inside a rotating sphere. New J. Phys., 9, 303, doi: 10.1088/1367-2630/9/8/303 .Mininni, P. D., 2007: Inverse cascades and alpha effect at a low magnetic Prandtl number. Phys. Rev. E, 76, 026316, doi: 10.1103/PhysRevE.76.026316.1 Mininni, P., A.. Alexakis, A. Pouquet, 2007: Energy transfer in Hall-MHD turbulence, cascades, backscatter and dynamo action. J. Plasma Phys., 73, 377-401, doi: 10.1017/S0022377806004624.1 Mininni, P., A. Alexakis, A. G. Pouquet, 2008: Scale interactions in hydrodynamic turbulence at large Reynold numbers. IUTAM Book Series: IUTAM Symp. Comput. Phys. And New Perspectives in Turb., Kaneda, Y, Eds., Springer-Verlag, 4, 125-130, doi: 978 1-4020-6471-5. P.D. Mininni, E. Lee, A. Norton, and J. Clyne, Flow visualization and field line advection in computational fluid dynamics: application to magnetic fields and turbulent flows, New J. Phys. 10(12), 125007/1-23 (2008). P. Mininni, P. Sullivan and A. Pouquet,``Two examples from geophysical and astrophysical turbulence on modeling disparate scale interactions,' Summer school on mathematics in geophysics, Roger Temam and Joe Tribbia Eds., Springer Verlag, to appear (2009). C. S. Ng, D. Rosenberg, K. Germaschewski, A. Pouquet and A. Bhattacharjee,``A comparison of spectral element and finite difference simulations with adaptive mesh refinement for the MHD island coalescence instability problem,' to appear,

Astrophys. J. Suppl. (2009). Yannick Ponty, Pablo D. Mininni, Jean-Philipe Laval, Alexandros Alexakis, Julien Baerenzung,Francois Daviaud, Berengere Dubrulle, Jean-Fran cois Pinton, Helene Politano and Annick Pouquet, ``Linear and non linear features of the Taylor-Green Dynamos,' Comptes Rendus de l'Academie des Sciences (Paris), 9, 749 (2008). Ponty, Y., P. D. Mininni, J.-F. Pinton, H. Politano, A. Pouquet, 2007: Dynamo action at low magnetic Prandtl numbers: Mean flow versus fully turbulent motions. New J. Phys., 9, 296, doi: 10.1088/1367-2630/9/8/296.3 Pouquet, A. G., A. Alexakis, P. Mininni, D. Montgomery, 2008: Dynamics of the small scales in magnetohydrodynamic turbulence. IUTAM Book Series: IUTAM Symp. Comput. Phys. And New Perspectives in Turb., Kaneda, Y, Eds., SpringerVerlag, 4, 305-312, doi: 978 1-4020-6471-5. Rosenberg, D., A. Pouquet, P. D. Mininni, 2007: Adaptive mesh refinement with spectral accuracy for MHD in two space dimensions. New J. Phys., 9, 304, doi: 10.1088/1367-2630/9/8/304 Wang, H., J. J. Tribbia, F. Baer, A. Fournier, M. A. Taylor, 2007: A spectral element version of CAM2. Mon. Wea. Rev., 135, 37 3825-3840. Thanks to the team! And thank you all for your attention 38 39 As an example: Summary of the GTP workshop on

Turbulence & Scalar Transport in Roughness Sub-layers (RSLs) Jielun Sun et al., ESSL-MMM Types of roughness elements considered include: Vegetated canopies Urban and suburban environments Underwater plant communities Ocean waves Wind farms Although there are similarities, profound differences in turbulence structures are found among these RSLs depending on rigidity and porosity of roughness elements Over-ocean RSLs are strongly affected by speed and direction of swell and can impact the entire PBL. Imprint of urban geometry greatly impacts turbulence structures in RSL due to building shapes and distributions.

Underwater RSLs due to aquatic vegetation can fill entire channel depth. Past, present & future experiments : e.g., HATS, O-HATS, 40 C-HATS, A-HATS