Coupling of the met.no ice model to MICOM

Norwegian Meteorological Institute met.no

Coupling of the met.no ice model to MICOM

Jens Debernard

Presented at LOM-meeting, 26.-28.1.2005, Miami

Norwegian Meteorological Institute met.no

Coupling of the met.no ice model to MICOM and MIPOM

Jens Debernard

Presented at LOM-meeting, 26.-28.1.2005, Miami

Norwegian Meteorological Institute met.no

Overview

1. The sea ice model MI-IM2. Differences when coupling with

MICOM or MIPOM3. Inertial oscillations4. Some results from a regional

coupled atmosphere and ocean system.

5. Summary

Norwegian Meteorological Institute met.no

The met.no ice model MI-IM

• 3-layer Semtner-type model

• Prognostic equations for: ice volume, snow volume, ice concentration, internal heat of the ice

• EVP dynamics• Positive definite

advection (non-oscillatory MPDATA)

• Discretized at C-grid• Soon: MPI-parallelized

Norwegian Meteorological Institute met.no

The met.no ice model MI-IM

• 3-layer Semtner-type model

• Prognostic equations for: ice volume, snow volume, ice concentration, internal heat of the ice

• EVP dynamics• Positive definite

advection (non-oscillatory MPDATA)

• Discretized at C-grid• Soon: MPI-parallelized

Norwegian Meteorological Institute met.no

Conservation of mass•Ice volume

•Snow volume

•Ice area (concentration)

H(x) = 0, x < 0 and H(x) = 1, x > 0

Norwegian Meteorological Institute met.no

Sea ice as a heat reservoir between the atmosphere and the ocean

A - Ice concentrationh – Ice thickness

Qoi

Qai

Qoa

Qao

Norwegian Meteorological Institute met.no

MI-IM coupled to the ocean models:

• MICOM• MIPOM Or MI-POM

(the met.no version of the POM)

Norwegian Meteorological Institute met.no

MICOM vs MIPOM

Norwegian Meteorological Institute met.no

Thermodynamical coupling, 1

• MICOM: Omstedt & Wettlaufer, JGR, 1992

Qoi = Ocpw cht|VVii-Vo|(TO – Tf), Tf = mSio, cht=2x10-4

• MIPOM: Mellor & Kantha, JGR, 1989

Qoi = Ocpw ctZ(TO – Tf)

ctz = u*/[Prt -1ln(z/z0)+b (z0u*/)1/2 Pr2/3]Prt = 0.85, Pr = 12.9, b = 3.14

Norwegian Meteorological Institute met.no

Thermodynamical coupling, 2

• MICOM: Omstedt & Wettlaufer, JGR, 1992

Qoi = Ocpw cht|VVii-Vo|(TO – Tf), Tf = mSio

Fs = [u*/(3.0 Sc)] (S0 – Sio)Sc = 2432

• MIPOM: Mellor & Kantha, JGR, 1989

Qoi = Ocpw ctZ(TO – Tf)

ctz = u*/[Prt -1ln(z/z0)+b (z0u*/)1/2 Pr2/3] Prt = 0.85, Pr = 12.9, b = 3.14

FS = Csz(SO – Sio)

csz = u*/[Prt -1ln(z/z0)+b (z0u*/)1/2 Sc2/3]

Norwegian Meteorological Institute met.no

Dynamical coupling

• MICOM: Tio = O cdio|Vi-Vo|[ (Vi-Vo)cos() + k x (Vi-Vo) sin()]

cdio ≈ 5x10-3 , ≈ 23º

• MIPOMTio = O cdz |Vi-Vo| (Vi-Vo)

cdz = u*/(-1ln(z/z0))

Norwegian Meteorological Institute met.no

Coupling time-scheme

T1

MI-IM MICOM or MIPOM

FT,FS,T(x),T(y) TO,SO,UO,VO,HS,Wfrz

FT,FS,T(x),T(y) TO,SO,UO,VO,HS,Wfrz

T1

T2 T2

Norwegian Meteorological Institute met.no

Inertial oscillations

• We have experienced problems in MICOM with unstable inertial oscillations due to the stress turning term in a C-grid. – No problems for dynamical coupling

time-steps > 12 h (2/f). • MIPOM can be unstable for very thin

surface sigma-layers. – Implicit calculation of ice-ocean stress

inside MIPOM is required

Norwegian Meteorological Institute met.no

1992 02

Norwegian Meteorological Institute met.no

1993 02

Norwegian Meteorological Institute met.no

1994 02

Norwegian Meteorological Institute met.no

1995 02

Norwegian Meteorological Institute met.no

1996 02

Norwegian Meteorological Institute met.no

Summary

• Different vertical representation of the upper ocean is the fundamental difference between the coupling to MICOM and MIPOM.– Coupling should be easier in z-level or hybrid-

layer models with a reasonable resolved, equidistant grid-spacing in the upper ocean.

• Unstable inertial oscillations may occur in both types of systems but they are avoidable.

• Ice models like MI-IM has to be tuned to give a realistic amount of sea ice, both in stand-alone ice-ocean simulations and when coupled to atmosphere models.

Norwegian Meteorological Institute met.no

END