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Science application and test case
•In order to validate the code changes and to demonstrate the improvement on HYCOM, one needs to configure a scientifically useful case.
•HYCOM has been implemented as an ESPC ocean component in a standalone configuration on a Parallel Ocean Program (POP) glbx1v6 dipolar grid (320x384) grid and bathymetry. This configuration is a 1-degree climate case from the Community Earth System Model (CESM) also used by CICE in order to provide a direct comparison to simulations performed by the CESM model.
•Several routines of the HYCOM source code (v2.2.86) have been modified to include the proper reading of the CORE-II forcing and a new passive ice component has been added, based on the CESM DICE.
•Several 30-year runs of HYCOM have been performed with the CORE-II (Large and Yeager, 2009) normal year atmospheric fields to assess the sensitivity of the model to several parameters (reference pressure, thermobaricity, and isopycnal smoothing).
Set-up
CCSM3-HYCOM: - CORE-II Atmospheric forcing from 1948 to 2007 through the CCSM coupler (5 Cycles)- Dipole POP gx1v3 grid- Initialization from rest with Levitus PHC2.1 (POPx1v3 initial conditions)- SSS-relaxation:4year/50m everywhere- Normalization of the salt flux at the surface- Bulk Formulation :Large and Yeager- CSIM ice model
FSU-HYCOM: - CORE-II Atmospheric forcing from 1948 to 2007 (5 Cycles) - Tripolar HYCOM GLBt0.72 grid- Initialization from rest with Levitus PHC2.1- SSS-relaxation: 4year/50m everywhere except Antarctic at 6months/50m- Normalization of the salt flux at the surface- Bulk Formulation : Large and Yeager - CICE ice model
Mixed Layer depth
New FSU-HYCOMCCSM3-HYCOMPOP-NCAR
MLD 0.125kg/m3 criterium in March average over 1988-2007, last cycle
0. 3.km
HYCOM in CESM implementation
Goal #1: Produce a HYCOM stand-alone baseline run in a C-compset (use of DICE for the ice component) : • based on 1º resolution grid from the POP gx1v6 grid (320x384),• v2.2.86 of the HYCOM source • Initial Conditions Levitus- PHC2• CORE atmospheric forcing Normal Year • Ice component: DICE (new in HYCOM)• Precipitation adjustment (new in HYCOM)• Spatially varying SSS/SST relaxation
For comparison purposes, POP-DICE has been run in its default setting for 30 years (data provided by Caroline Papadopoulos and Julie McClean)
Evolution of Global T &S
With precip_adjust:Stabilization of S
REF-POP: eq. to -3% of precipREF-HYCOM: -2% of precip
HYCOM in CESM implementation
Goal #2: Produce a HYCOM-CICE stand-alone baseline run in a G-compset : • based on 1º resolution grid from the POP gx1v6 grid (320x384),• v2.2.86 of the HYCOM source • Initial Conditions Levitus- PHC2• CORE atmospheric forcing Normal Year • Ice component: CICE v4.0 (initial condition: default ice cap provided by CICE)• Precipitation adjustment• Spatially varying SSS/SST relaxation
•Results are compared with HYCOM-DICE (REF-HYCOM)
Evolution of T & S, AMOC strength
HYCOM-CICE (black)REF-HYCOM (Yellow)
HYCOM-CICE (black)REF-HYCOM (yellow)
HYCOM-CICE stabilizes before REF-HYCOM
HYCOM-CICE shows a stronger AMOC at 16Sv than REF-HYCOM (12sv)
HYCOM in CESM implementation
Produce a CESM-HYCOM baseline run in a G-compset : • based on 1º resolution grid from the POP gx1v6 grid (320x384),• v2.2.35 of the HYCOM source (for testing purposes) • Initial Conditions Levitus- PHC2• CORE-II atmospheric forcing provided by DATM• Ice component: CICE v4.0 (CESM version)
(Ice initial condition: ice cap provided by CESM)
Results to be compared with:• CESM-POP• HYCOM-CICE stand-alone
Comparison of the total heat and freshwater fluxF
res
hw
ate
r F
lux
Hea
t F
lux
Comparison of the total heat and freshwater flux (monthly mean Jan/ 1st year)