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A Hybrid Coordinate Ocean Model (HYCOM) For Data-Assimilative Ocean Modeling

A Hybrid Coordinate Ocean Model (HYCOM) For Data-Assimilative Ocean Modeling. A Hybrid Coordinate Ocean Model (HYCOM) For Data-Assimilative Ocean Modeling. RSMAS August 19, 2002.

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A Hybrid Coordinate Ocean Model (HYCOM) For Data-Assimilative Ocean Modeling

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  1. A Hybrid Coordinate Ocean Model (HYCOM) For Data-Assimilative Ocean Modeling A Hybrid Coordinate Ocean Model (HYCOM) For Data-Assimilative Ocean Modeling RSMAS August 19, 2002

  2. A multi-institutional effort on the development and evaluation of a data-assimilative hybrid isopycnal-sigma-pressure (generalized coordinate) ocean model (called Hybrid Coordinate Ocean Model or HYCOM.) • The partnering/collaborating organizations are the University of Miami/RSMAS, the Naval Research Laboratory, NOAA/AOML, the Los Alamos National Laboratory, NERSC, LEGI, the Service Hydrographique et Océanographique de la Marine (SHOM), NAVOCEANO, Planning Systems Inc., Orbital Image Corp., and the U.S.Coast Guard.

  3. The primary computational goal is the establishment of a global eddy-resolving real-time ocean forecast system with sophisticated data assimilation techniques that can be efficiently executed on massively parallel computers

  4. THREE MAJOR COMPONENTS: • The ocean model: the HYbrid Coordinate • Ocean Model (HYCOM) • In-situ and satellite data • 3. Data assimilation techniques

  5. Background • -Rotating and stratified fluids =>dominance of • lateral over vertical transport. • -Hence, it is traditional in ocean modeling to orient • the two horizontal coordinates orthogonal to the • local vertical direction as determined by gravity. • -The choice of the vertical coordinate system is the • single most important aspect of an ocean model's • design (DYNAMO, DAMÉE-NAB). • -The practical issues of representation and • parameterization are often directly linked to the • vertical coordinate choice(Griffies et al., 2000).

  6. Currently, there are three main vertical coordinates in use, none of which provides universal utility. Hence, many developers have been motivated to pursue research into hybrid approaches.

  7. HYCOM The hybrid coordinate is one that is isopycnal in the open, stratified ocean, but smoothly reverts to a terrain-following coordinate in shallow coastal regions, and to pressure coordinate in the mixed layer and/or unstratified seas.

  8. HYCOM

  9. HYCOM The capability of assigning additional coordinate surfaces to the oceanic mixed layer allows for sophisticated closure scheme, such as the K-Profile Parameterization (KPP).

  10. HYCOM 2.1 • - Add halos for MPI to automatically support periodic • boundaries • - Support nested-domain open boundaries • Fully global (Pan-Am grid) • Alternative mixed layer models (G. Halliwell presentation) • Mellor-Yamada 2.5 • Price-Weller-Pinkel • - Orthogonal curvilinear grids • - Single passive tracer • - NetCDF output files • To be released in September 2002 • Other numerical developments (M. Iskandarani presentation)

  11. WEB PAGE: http://hycom.rsmas.miami.edu Coordinator: Eric P. Chassignet (echassignet@rsmas.miami.edu)

  12. NORTH ATLANTIC BASIN-SCALE SIMULATIONS • Based on the CME, DYNAMO and MICOM experience (1˚, 1/3˚ and 1/12˚, respectively) • The CME comparison is completed (sigma-theta, • sigma2, and sigma2 + thermobaricity) [Chassignet • et al., to be submitted] • 1/3˚ routine (interannual forcing – 40 years) [Hogan] • 1/12˚ in progress (years 1999-2002 after spin-up) • [Hogan, Wallcraft, Chassignet, Hurlburt] NORTH ATLANTIC REGIONAL SIMULATIONS • Intra-American (Caribbean) Sea (standard configuration • for data assimilation testing) [Townsend, Wallcraft]

  13. High-resolution 1/12° North Atlantic HYCOM simulation ECMWF forcing

  14. Atlantic Model Configuration • Horizontal grid: 1/12˚ (1678 x 1609 grid points, 6 km spacing on • average) • 28°S to 70°N (including the Mediterranean Sea) • 26 vertical coordinate surfaces (σ-theta reference) • Bathymetry: Quality controlled ETOPO5 • Surface forcing: wind stress, wind speed, heat flux (using bulk • formula), E-P + relaxation to cllimatological surface salinity • River runoff included • Buffer zone: ~3° band along the northern and southern boundaries • with relaxation to monthly climatological T and S (Levitus)

  15. 10 x 16 Equal Ocean Decomposition • Running on Brainerd (ARL) • 58,000 CPU hrs/model year on 160 CPUs • 770 GB/model year for daily 3-D output • MPI parallelization

  16. Sea Surface Temperature Sea Surface Height 1/12° HYCOM ATLANTIC SIMULATION ~7 km resolution at mid-latitudes Forced by ECMWF 10 m reanalysis monthly climatological wind and thermal fluxes, climatological surface salinity and relaxation to MODAS climatology at the northern and southern boundaries (themohaline component)

  17. 18 degree Mode Water formation

  18. 18 degree Mode Water formation

  19. 1/12° Atlantic HYCOM Deep Western Boundary Current

  20. Denmark Straits Overflow Region Observed transport from current meters Dickson and Brown 1994 (JGR) 5.2 10.7 13.3 Model transport sum layers 20-26 ρ > 27.8 (NADW) 1/12° North Atlantic HYCOM 4.14 9.36 13.77 layer 20 mean speed

  21. Denmark Straits Overflow Cold fresh water forms over shelf in Nordic Seas and spills over the Denmark Strait and entrains more saline Labrador Sea water

  22. OPEN BOUNDARY CONDITIONS IN HYCOM • No distinction is made between inflow and outflow boundaries • The “well-posed” boundary conditions developed by Browning • and Kreiss (1982) are applied to the barotropic mode, i.e., the • barotropic pressure and velocities are advected into/out of the • domain via characteristics • Relaxation to mass fluxes, interface depths, T, S, and density • is prescribed in a finite-width sponge zone

  23. HYCOM Nesting Applied to IAS [Townsend, Wallcraft] North Atlantic, 0.32° North Atlantic, 0.32° SST CI = 0.08° C May 4 Intra-Americas Sea, 0.08° SST CI = 0.3° C Jan 16 SST CI = 0.08° C May 4

  24. Meridional Velocity, De Soto Canyon, Gulf of Mexico at 29.6N 0.32° North Atlantic HYCOM Jul 14 0.08° Intra-Americas Sea HYCOM Jul 14 Forced by 1979-1993 Monthly Mean ECMWF Reanalysis 10 m winds and boundary conditions from the 0.32° North Atlantic HYCOM

  25. 0.32° North Atlantic HYCOM Jan 16 0.08° Intra-Americas Sea HYCOM Jan 16

  26. Atlantic regional modeling • Coastal seas around Florida Bay [Kourafalou] • A nested approach is proposed for a high resolution • HYCOM application around south Florida • (large scale– regional scale– coastal scale) • The regional model will provide boundary conditions for • limited area hydrodynamic, ecosystem and water quality • models in Florida Bay • The simulations will be closely linked to ongoing • observational studies in Florida Bay and adjacent seas

  27. The seas adjacent to Florida Bay: Gulf of Mexico, West Florida Shelf and Florida Straits (the shaded area marks the regional model domain) • Physical transport processes impose strong hydrodynamic links between Florida Bay and the adjacent coastal seas. • Significant transient inputs can reach Florida Bay from remote regions of the Gulf of Mexico.

  28. Recent observational studiesprovide evidence of transport processes linking south Florida coastal ecosystems

  29. A comprehensive, multi-year, interdisciplinary data set is available for model initialization, forcing and validation

  30. Atlantic regional modeling • SEED [Jacobs] Slope To Shelf Energetics And Exchange Dynamics To understand the mechanisms that transfer properties (energy, mass, momentum, heat, salt, …) across the shelf slope Focus Area Gulf of Mexico, Mississippi Bight, west of the DeSoto Canyon

  31. Atlantic regional modeling • DIADEM/TOPAZ [Evensen] Implement and validate a model system for hindcast simulations in the Faroe-Shetland channel Run the system in a multiyear hindcast simulation to produce current statistics which can be used to derive design criteria for optimal rig-selection and design

  32. Atlantic regional modeling • Hurricane impact on mixed layer properties • [Jacob, Shay, Halliwell] Effects of the entrainment closure on the oceanic mixed layer response during a tropical cyclone passage

  33. Hycom Q Movie Gaspar KPP MY2.5 PWP

  34. PACIFIC BASIN-SCALE SIMULATIONS - 1/12° in progress [Metzger, Hurlburt] PACIFIC REGIONAL SIMULATIONS • - 1/8° to 1/32° Japan/East Sea [Hogan, Hurlburt] • - 1/32° East Asian Seas [Hogan]

  35. PACIFIC MODEL CONFIGURATION • Horizontal grid: 1/12° ( 2294 x 1362 grid points, 6.5 km spacing on average) • 20°S to 65.8°N • 20 vertical coordinates (σ-theta reference) • Bathymetry: Quality controlled ETOP05 • Surface forcing: • wind stress, wind speed, heat flux (using bulk formula), • E-P + relaxation to climatological SSS • • River runoff • • Buffer zone: ~3° band along southern and eastern • boundary with relaxation to monthly climatological T • and S • Closed boundaries along 20°S, in the Indonesian • throughflow region and in the Bering Strait

  36. 22 x 13 Equal Area Decomposition (all land tiles discarded) • Running on ------- (MHPCC) • 50,000 hrs/model year on 207 CPUs • 288 GB/model year for 3-D fields every 3 days • MPI parallelization

  37. 1/12° Pacific HYCOM SSH Snapshot – 17 December Forced with climatological HR winds and ECMWF thermal forcing

  38. 1/12° Pacific HYCOM SSH and SST Snapshot – 17 December Forced with climatological HR winds and ECMWF thermal forcing

  39. Mean Sea Surface Height 1/12° Pacific HYCOM vs. Observations Qu et al. (2001, JPO)

  40. Velocity Cross-section Across Luzon Strait Sb-ADCP data versus 1/12° Pacific HYCOM in the upper 300m 120.75°E 18.5-22°N Transport 3.3 Sv 4.4 Sv Sb-ADCP data from Liang et al. (DSR Part II, in press) HYCOM is forced with high-frequency HR winds and ECMWF thermal forcing

  41. Velocity Cross-section Along Luzon Strait Sb-ADCP data versus 1/12° Pacific HYCOM in the upper 300m 118.5-124.5°E 21.0°N Sb-ADCP data from Liang et al. (DSR Part II, in press) HYCOM is forced with high-frequency HR winds and ECMWF thermal forcing

  42. 1/12° Pacific HYCOM Impact of Hurricane Julliette (Zamudio, Hurlburt, Metzger) SSH SST

  43. Plans for JES/EAS Modeling [Hogan, Hurlburt] 1/32° Japan/East Sea (ONR JES DRI) • Branching of Tsushima Warm Current • Nearshore Branch Dynamics • Water mass formation (ESIW) • Model-data comparisons • Impact vertical coordinate configuration • Data assimilation 1/32° East Asian Seas (LINKS) • Ability of HYCOM to robustly simulate shelf (Yellow Sea) and • deep (JES) environment • Branching of Tsushima Warm Current from the Kuroshio • (where, how, etc.) • Interaction of coastal and large-scale currents

  44. Japan/East Sea 1/16˚ Surface Japan/East Sea 1/8˚ Surface Japan/East Sea 1/16˚ Deep

  45. 1/32° HYCOM East Asian Seas Model Nested inside 1/8° HYCOM Pacific Basin Model Boundary conditions via one-way nesting and 6 hrly ECMWF 10 m atmospheric forcing

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