nansen environmental and remote sensing center modifications of the micom version used in the bergen...
DESCRIPTION
Nansen Environmental and Remote Sensing Center BCM components and configuration MICOM Based on version 2.8 Horizontal resolution of ~1.5° with enhanced meridional resolution near the equator and the northern hemisphere grid singularity located over Siberia. 35 model layers Reference pressure at the surface Dynamic-thermodynamic sea ice modules included ARPEGE Spectral model. Hybrid vertical coordinate (terrain following/pressure). Can use semi-Lagrangian time integration. Horizontal resolution: T63 (~2.8°) 31 model layers.TRANSCRIPT
![Page 1: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/1.jpg)
Nansen Environmental andRemote Sensing Center
Modifications of the MICOM version used in the Bergen Climate Model
Mats Bentsen and Helge Drange
Nansen Environmental and Remote Sensing CenterBjerknes Centre for Climate ResearchNansen-Zhu International Research Centre, Beijng
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Nansen Environmental andRemote Sensing Center
Outline
• BCM components and configuration• Conservation• Physical parameterizations• Some results
![Page 3: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/3.jpg)
Nansen Environmental andRemote Sensing Center
BCM components and configuration
MICOM• Based on version 2.8• Horizontal resolution of ~1.5° with enhanced meridional resolution near the equator and the northern hemisphere grid singularity located over Siberia.• 35 model layers• Reference pressure at the surface• Dynamic-thermodynamic sea ice modules included
ARPEGE• Spectral model.• Hybrid vertical coordinate (terrain following/pressure).• Can use semi-Lagrangian time integration.• Horizontal resolution: T63 (~2.8°)• 31 model layers.
![Page 4: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/4.jpg)
Nansen Environmental andRemote Sensing Center
Main motivations for MICOM improvements
• Get rid of flux adjustments or at least reduce the magnitude of the adjustments.• Improve the Southern Ocean sea-ice extent and volume.• Improve Arctic sea-ice volume and summer extent.• Reduce model drift.• Add features required by IPPC.
![Page 5: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/5.jpg)
Nansen Environmental andRemote Sensing Center
MICOM conserves total mass, but not mass within each layer!
Red dotted lines:After layer advection
Blue lines:After bottom pressure restoration
Conservation of layer mass
![Page 6: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/6.jpg)
Nansen Environmental andRemote Sensing Center
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Method 1 to reduce the bottom pressure error
![Page 7: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/7.jpg)
Nansen Environmental andRemote Sensing Center
Method 2 to reduce the bottom pressure error
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Layer mass before advection:
Layer mass after advection and with of correction to restore thebottom pressure:
Apply correction to layer thickness so layer mass is conserved:
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![Page 8: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/8.jpg)
Nansen Environmental andRemote Sensing Center
Advection/diffusion of temperature and salinityin an isopycnic layer
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In the continuous case:• Isopycnic advection does not lead to density change• Isopycnic diffusion increases density (cabbeling)
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![Page 9: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/9.jpg)
Nansen Environmental andRemote Sensing Center
• Density changes due to lateral diffusion is compensated by diapycnal fluxes.
• Layer density can deviate from the target density, but the latter is used in computing the pressure gradient.
• The remaining density deviation from target density is kept small by relaxing the water mass towards a water mass with correct density.
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![Page 10: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/10.jpg)
Nansen Environmental andRemote Sensing Center
Mean salinity (upper figure) and temperature (lower figure) in asimulation with BCM
![Page 11: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/11.jpg)
Nansen Environmental andRemote Sensing Center
Turbulent fluxes
The ocean surface velocity is now included in the computation of turbulent fluxes.
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![Page 12: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/12.jpg)
Nansen Environmental andRemote Sensing Center
Left/right figure show snapshots of SST (C°) without/with ocean surfacevelocities included in the computation of turbulent fluxes.
Time series of SST in the region [5S,5N] and[120W,90W]. Green curve is climatology whileblue/red curve is without/with ocean surfacevelocitiy dependent turbulent fluxes.
![Page 13: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/13.jpg)
Nansen Environmental andRemote Sensing Center
Left figure is monthly mean SST with region and coloring as previous figure.
Right figure show eastward surface velocity in the same region. Coloring as before.
![Page 14: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/14.jpg)
Nansen Environmental andRemote Sensing Center
Conceptual presentation of convective adjustment
Old scheme New scheme
![Page 15: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/15.jpg)
Nansen Environmental andRemote Sensing Center
![Page 16: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/16.jpg)
Nansen Environmental andRemote Sensing Center
Diapycnal mixing
Old code:• Background mixing (diffusivity ~1/N)
New code:• Background mixing (diffusivity ~1/N)• Shear instability mixing (Ri dependent, Large et. al 1994)• Gravity current entrainment (Ri dependent, Turner 1986)• Cabbeling (due to lateral mixing)• Momentum mixing (Pr=10)
Absorption of short-wave radiation below mixed layer
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Nansen Environmental andRemote Sensing Center
Monthly mean SST and sea-ice cover from transient BCM simulation
March 1940 September 1940
![Page 18: Nansen Environmental and Remote Sensing Center Modifications of the MICOM version used in the Bergen Climate Model Mats Bentsen and Helge Drange Nansen](https://reader036.vdocuments.site/reader036/viewer/2022062600/5a4d1bbd7f8b9ab0599d1d15/html5/thumbnails/18.jpg)
Nansen Environmental andRemote Sensing Center
Monthly mean SST and sea-ice cover from transient BCM simulation
September 1940March 1940
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Nansen Environmental andRemote Sensing Center
Monthly mean SSS from transient BCM simulation
September 1940March 1940
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Nansen Environmental andRemote Sensing Center
Monthly mean barotropic stream function from transient BCM simulation
March 1940 September 1940