NEMO Great Lakes simulations

By: Oleksandr (Sasha) Huziy, Luis Duarte

Outline

• Experimental setup and driving data

• Seasonal climatologies

• SST and SSH timeseries

• Vertical structure of lake temperature

• Some results of a 30 year simulatoin (1958-1987)

• Questions

Configuration summary

• Horizontal resolution: 0.1 degree, \(170\times90\) gridpoints (Rotated lat/lon projection)

• 35 vertical levels with partial steps at the bottom. Level thickness gradually increases from 25 cm at the surface to 30 m at the bottom

• Time step: 1 hour (Scaled accordingly following Dupont et al 2012, who used 600 s at 2km horizontal resolution)

• Model version: 3.4

Fig: Simulation domain and Bathymetry

Physical parameterisations/options that work for us

• Surface pressure gradient term is treated by filtering EGWs.

  (Roullet and Madec 2000, preprocessor key: key_dynspg_flt)

• Fresh water fluxes are corrected in a way that mean annual fresh water flux is 0.

  \[E-P-R = 0\]

• The list of keys used to compile the model.

  key_trabbl	key_lim2	key_ldfslp
  key_dynldf_c3d	key_zdftke	key_zdfddm
  key_dynspg_flt	key_traldf_c2d

Relevant namelist parameters

• TVD scheme used for tracer advection

• lateral diffusion scheme for tracers

  • laplacian operator

  • rn_aht_0 = 2.5 ! horizontal eddy diffusivity for tracers \([{\rm m^2/s}]\)

• lateral diffusion on momentum

  • laplacian operator

  • rn_ahm_0_lap = 50.0 ! horizontal laplacian eddy viscosity \([{\rm m^2/s}]\)

Driving data

• DFS5.2 (Drakkar Forcing Set) available for 1958-2012

• Variables:

  • wind components at 10 m, 3-hourly

  • temperature and humidity of air at 2m, 3-hourly

  • Longwave and shortwave radiation fluxes, daily

  • Snowrate and precipitation, daily

Driving data: wind at 10m [m/s]

Simulated seasonal SST

Ice fraction

Mixed layer depth

Simulated Annual mean surface velocities

Simulated seasonal surface velocities (DJF)

Simulated seasonal surface velocities (MAM)

Simulated seasonal surface velocities (JJA)

Simulated seasonal surface velocities (SON)

Temperature (spinup)

Ice fraction

Sea surface height (timeseries, spinup using climatological forcing)

Lake Superior (Temperature, verical cross-section \({\rm ^{\circ}C}\))

Lake Michigan (Temperature, verical cross-section \({\rm ^{\circ}C}\))

Lake Huron (Temperature, verical cross-section \({\rm ^{\circ}C}\))

Results of a 30 year (1958-1987) simulation started from the spinup