A QUASI-GLOBAL CONFIGURATION OF ROMS (OR, TOWARDS A QUASI-GLOBAL CONFIGURATION OF ROMS (OR, TOWARDS GOMSGOMS?)?)

Guillermo Auad & Art Miller (CRD/SIO)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).

OrganizationOrganization

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 coefficientScaling 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 restusing (3).

Minimum Viscosity Coeff. (visc2) vs. LatitudeMinimum Viscosity Coeff. (visc2) vs. Latitude

Ah=Ah(φ,dx)

MODEL's TOTAL KINETIC ENERGY vs. TIMEMODEL's TOTAL KINETIC ENERGY vs. TIME

ROMSMGSVA

Gulf Stream, Antilles Curr.,Gulf Stream, Antilles Curr.,Loop Current & Labrador Curr.Loop Current & Labrador Curr.

Kuroshio, Oyashio, Liman, Tsuchiya & Tsugaru CurrentsKuroshio, Oyashio, Liman, Tsuchiya & Tsugaru Currents

from MGSVA

Malvinas-Brasil Confluence AreaMalvinas-Brasil Confluence Areasummer winter

TROPICAL PACIFIC CURRENTS AND SSTTROPICAL PACIFIC CURRENTS AND SST

Tropical Instability WavesTropical Instability Waves

Across-equator zonal velocity profilesAcross-equator zonal velocity profiles(152(152°W – Hawaii-Tahiti transect)°W – Hawaii-Tahiti transect)

From Johnson & Luther (1994) -current meter data

ROMS

150 m

Surface

Winter Flows Winter Flows off Californiaoff California

STRAIT OF GIBRALTARSTRAIT OF GIBRALTAR

Mean speed from ROMS

Mean speed fromobs (ADCP)

Guinea, Equatorial and Angola CurrentsGuinea, Equatorial and Angola Currents

MGVSA

TRANSPORT THROUGH DRAKE PASSAGETRANSPORT THROUGH DRAKE PASSAGE

Malvinas

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

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

ROMS: 128 Sv

ANTARCTIC CIRCUMPOLAR CURRENTANTARCTIC CIRCUMPOLAR CURRENT

(from L. Talley, SIO)

Global Salinity Minimum

Global ROMS

SEA LEVEL COMPARISON AT SAN FRANCISCOSEA LEVEL COMPARISON AT SAN FRANCISCO

CLIMATIC INDEXES FROM 56-y RUN:CLIMATIC INDEXES FROM 56-y RUN:PDO and NIPDO and NIÑO3.4ÑO3.4

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 ROMSPlanned 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