a quasi-global configuration of roms (or, towards goms ?) guillermo auad & art miller (crd/sio)
DESCRIPTION
A QUASI-GLOBAL CONFIGURATION OF ROMS (OR, TOWARDS GOMS ?) Guillermo Auad & Art Miller (CRD/SIO) Grid features : zonal resolution : 0.8 º (fixed); meridional resolution : 0.3 to 0.7º (slowing varying: ∆ resolution < 1.5% ); vertical resolution : 20 levels. - PowerPoint PPT PresentationTRANSCRIPT
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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).
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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
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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).
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Minimum Viscosity Coeff. (visc2) vs. LatitudeMinimum Viscosity Coeff. (visc2) vs. Latitude
Ah=Ah(φ,dx)
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MODEL's TOTAL KINETIC ENERGY vs. TIMEMODEL's TOTAL KINETIC ENERGY vs. TIME
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ROMSMGSVA
Gulf Stream, Antilles Curr.,Gulf Stream, Antilles Curr.,Loop Current & Labrador Curr.Loop Current & Labrador Curr.
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Kuroshio, Oyashio, Liman, Tsuchiya & Tsugaru CurrentsKuroshio, Oyashio, Liman, Tsuchiya & Tsugaru Currents
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from MGSVA
Malvinas-Brasil Confluence AreaMalvinas-Brasil Confluence Areasummer winter
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TROPICAL PACIFIC CURRENTS AND SSTTROPICAL PACIFIC CURRENTS AND SST
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Tropical Instability WavesTropical Instability Waves
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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
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150 m
Surface
Winter Flows Winter Flows off Californiaoff California
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STRAIT OF GIBRALTARSTRAIT OF GIBRALTAR
Mean speed from ROMS
Mean speed fromobs (ADCP)
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Guinea, Equatorial and Angola CurrentsGuinea, Equatorial and Angola Currents
MGVSA
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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
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ANTARCTIC CIRCUMPOLAR CURRENTANTARCTIC CIRCUMPOLAR CURRENT
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(from L. Talley, SIO)
Global Salinity Minimum
Global ROMS
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SEA LEVEL COMPARISON AT SAN FRANCISCOSEA LEVEL COMPARISON AT SAN FRANCISCO
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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°)
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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