HYCOM 2.1 Development at RSMAS George Halliwell

HYCOM 2.1 Development at RSMASGeorge Halliwell

• HYCOM Development– Included several vertical mixing algorithms– Refine the hybrid vertical coordinate adjustment algorithm– Miscellaneous algorithms

• Ongoing HYCOM Evaluation and Analysis Efforts– Evaluate the vertical mixing algorithms– Evaluate other algorithms– Provided 1.4-degree Atlantic model to C. Thacker for data

assimilation studies– Climate studies

• Upper limb of Atlantic meridional overturning circulation• Modes of Atlantic Ocean response to NAO atmospheric forcing

• Planned HYCOM Evaluation and Analysis Efforts– West Florida shelf (with R. Weisberg and RSMAS HYCOM

group)– Hurricane response (with D. Jacob and N. Shay)– Coupled hurricane model (with S. Chen)– Florida Current (with C. Mooers and RSMAS HYCOM group)

Vertical Mixing Choices in HYCOM 2.1

• Vertical Mixing Models (surface to bottom)

– KPP– Mellor-Yamada level 2.5 turbulence closure

• Mixed Layer Models

– Kraus-Turner A (hybrid)– Kraus-Turner B (hybrid, simplified, from Bleck global HYCOM)– Kraus-Turner C (MICOM mode, from MICOM 2.8)– Price-Weller-Pinkel dynamical instability model

• Interior Diapycnal Mixing Models (for use with the mixed layer models)

– Explicit algorithm A (hybrid, MICOM-like)– Explicit algorithm B (MICOM mode, from MICOM 2.8)– Implicit algorithm (hybrid, KPP without surface b.l. model)

HYCOM Atlantic Ocean Simulations

• Domain– Atlantic Ocean, 20S to 62N– Resolution: 2.0 degrees horizontal, 22 layers vertical

• Forcing / Boundary Conditions / Initial Conditions– Surface forcing by COADS climatology– Relaxation to Levitus climatology at N/S boundaries– Relaxation to Levitus surface salinity– Initialized from p(latitude)

• Model Runs– 30-year spinup– One-year analysis run– Winter (mid-February) and summer (mid-August) fields saved

• Eight Cases Summarized Here to Illustrate Different Vertical Mixing Choices

2s

Latitude Latitude

Winter and summer cross-sections along 29W. The centralsigma-0 value in the alternating white and gray bands ofthe shading bar are the isopycnic reference values. Someof the layer numbers are shown inside the shading bar. Thethick line is the diagnosed mixed layer base.

Winter mixed layer thickness(m).

Experiments:

KPP (k-profile parameterization)MY (Mellor-Yamada 2.5)PWP (Price-Weller-Pinkel)KTAI (K-T A m.l., implicit diap.mix.)KTAIP (same with penetrating sw. rad.)KTAE (K-T A m.l., explicit diap. mix.)KTB (K-T B m.l., implicit diap. mix.)MIC (K-T C m.l., MICOM mode)

Winter barotropic stream-function (Sv)

Experiments:


Ekman spiralsproduced by theKPP and MYmixing modelsin the Westerlies(top) and thetrade Winds(bottom).

Produced from32-layer exp-eriments

Winter SST (C) for the KPPexperiment (top left). Otherwise,differences between the otherseven experiments and the KPPexperiment)

Experiments:


Experiments:


Summer SST (C) for the KPPexperiment (top left). Otherwise,differences between the otherseven experiments and the KPPexperiment)

Experiments:


Winter SSH (m) for the KPPexperiment (top left). Otherwise,differences between the otherseven experiments and the KPPexperiment)

Experiments:


Winter sigma-0 for the KPPexperiment (top left) alongA 29W cross-section.Otherwise, differencesbetween the other sevenexperiments and the KPPexperiment)

Experiments:


Winter SST differences (C)between the eight experimentsand Levitus climatology.

Experiments:


Summer SST differences (C)between the eight experimentsand Levitus climatology.

Experiments:


Winter sigma-0 differencesalong 29W between the eightexperiments and Levitusclimatology.

Figure: Preliminary simulation for the Gilbertcase using HYCOM including three non-slabSchemes: (a) mixed layer depth, (b) mixedlayer temperature, (c) zonal current,(d) meridional current, and e) surface fluxesto the atmosphere. The differences in thedirectly forced region are much largerbetween these schemes compared to thoseused in MICOM simulations. A surface fluxdifference of up to 500 Wm2 is seen at thepoint of closest approach of storm center. Red, Green, Blue and Cyan lines representquantities simulated using KT, KPP, MYand PWP schemes respectively.

Hurricanes and analysis regions for HYCOM simulations

Documents

HYCOM 2.1 Development at RSMAS George Halliwell