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									A QUASI-GLOBAL CONFIGURATION OF ROMS (OR, TOWARDS GOMS?)
                        Guillermo Auad & Art Miller (CRD/SIO)

Grid features:
●zonal resolution: 0.8º (fixed); meridional resolution: 0.3 to 0.7º (slowing
varying: ∆resolution < 1.5%); vertical resolution: 20 levels.
●Includes: fixed Iceshelf, topography from etopo2.

●Zonal walls at 80º (N & S).

●E-W periodic condition used at longitude 180º.




Runs carried out so far:

1.- Spin up climatological run from rest and Levitus T-S. (60-year long) driven
by NCEP/NCAR reanalysis wind stresses and heat fluxes.
2.- 56-year long hindcast run (i.e., climat. + anomalous winds and heat
fluxes), from 1948 to 2003 (finished a few days ago).
                        Organization

A minor code adaptation

Spin up of the model's total kinetic energy

Model output: main ocean currents of the World

A tough test: coastal flows

A tougher test: representation of a water mass: NPIW

2 climatic indexes in the Pacific Ocean: PDO and Nino3.4

Planned applications
                  Scaling of horizontal viscosity coefficient

goal: for each grid cell to proportionally (to its grid size) contribute potential vorticity to
western boundary layers.


                              ß ψx ~ Ah ψxxxx                                       (1)

but since Ah needs to satisfy a minimum value in order to yield realistic solutions
(Bryan, Manabe and Pacanowski, 1975):

                      Ah> 0.17 * ß* dx³                                      (2)

from (1) and (2) we can scale Ah as

                      Ah~ Ah0 (dx/dx0)**3 cos(φ)cos(φ0)                      (3)

where the subindex 0 marks the latitude, and viscosity of the largest grid size in the
domain (dx0).

In practice: Obtain Ah0 from (2) (i.e., for the largest grid size), and then obtain the rest
using (3).
Minimum Viscosity Coeff. (visc2) vs. Latitude


Ah=Ah(φ,dx)
MODEL's TOTAL KINETIC ENERGY vs. TIME
Gulf Stream, Antilles Curr.,
Loop Current & Labrador Curr.




                                 MGSVA
                          ROMS
Kuroshio, Oyashio, Liman, Tsuchiya & Tsugaru Currents
         Malvinas-Brasil Confluence Area
summer               winter          from MGSVA
TROPICAL PACIFIC CURRENTS AND SST
Tropical Instability Waves
 Across-equator zonal velocity profiles
 (152°W – Hawaii-Tahiti transect)




From Johnson & Luther (1994) -   ROMS
current meter data
                  150 m




Winter Flows
off California


                 Surface
       STRAIT OF GIBRALTAR

                       Mean speed from
Mean speed from ROMS   obs (ADCP)
Guinea, Equatorial and Angola Currents




                                 MGVSA
          TRANSPORT THROUGH DRAKE PASSAGE
                      Malvinas




Whitworth & Peterson (1985)(*)=134 13Sv

Various ACDP estimates from the
Univ. of Southampton=94Sv-155Sv

ROMS: 128 Sv
ANTARCTIC CIRCUMPOLAR CURRENT
 (from L. Talley, SIO)




                          Global ROMS

Global Salinity Minimum
SEA LEVEL COMPARISON AT SAN FRANCISCO
CLIMATIC INDEXES FROM 56-y RUN:
PDO and NIÑO3.4




                                             Corr=0.67; Coherence for 25y harmonic: 0.91 (10° phase)




  Corr=0.73; Coherence for 4y harmonic=0.78 (ampl=0.7 & phase =7°)
      Planned Applications of the Global ROMS

 Couple “GOMS” to an atmospheric model (ECPC fcsts)
 Use its output (climat & hincdast) as OBCs in regional models (a few latin
american scientists are interested in this)
 Sea level (*)& climatic studies.
 Studies on water mass formation (NPIW and Ross Sea area)


Future runs/planned improvements:
 Filter forcing with Killworth's matrix to obtain more realistic amplitudes (*)
(e.g., Nino3.4 index).
 Include sea-ice.


(*) underway

								
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