GENIE ExampleGENIE1expt

Tim Lenton (t.lenton@uea.ac.uk)

A simple experiment examining the effects of atmosphere parameters on climate and its sensitivity

Aim: To examine the spatial pattern of temperature for genie_eb_go_gs (default 36x36x8 grid), examine its sensitivity to varying parameters in the simple atmosphere model (EMBM), and evaluate the model climate sensitivity

Setting up the model

• You will be working with genie_eb_go_gs configuration
• Navigate to genie-main and open runtime_defaults.sh in order to see all model parameters
• Go to the EMBM (ea_...) parameters and note values of ea_12 to ea_15 which are all the parameters controlling the diffusion of heat and moisture
• Go to /configs and copy genie_eb_go_gs.config to genie_eb_go_gs_expt1.config (or similar)
• In the new config file change the EXPID to genie_eb_go_gs_expt1
• Set the run length to 2000 years by changing ma_koverall_total=1000000
  • (Note: this is the total number of atmospheric timesteps and by default the EMBM takes 5 timesteps per ocean timestep and the ocean takes 100 timesteps per year, therefore 500 timesteps per year for the EMBM and 500*2000=1000000)
• You need to control model data output. We recommend the following choices:
  • changing the frequency of ‘health checks’, by setting ea_3, go_3, gs_3 = 10000 (every 100 years, in goldstein timesteps)
  • changing the frequency of ‘full’ (or restart) model datatsets, by setting ea_4, go_4, gs_4 = 20000 (every 200 years, in goldstein timesteps – to give 10 datasets)
  • changing the frequency of timeseries output, by setting ea_5, go_5, gs_5 = 100 (to give annual 1 January snapshots)
  • if you want to change the frequency of netCDF averaged model output (initially every 10 years) to 100 years, then set ea_6, go_6, gs_6 = 10000 (in goldstein time steps)
• First we are going to run at pre-industrial (278ppmv) CO2 level, which requires no change to ea_20
• However, you can generate a unique instance of the model by varying key EMBM parameters ea_12 to ea_15. Some suggested reasonable ranges for these parameters are as follows:
  • ea_12 = 1.0e6 to 8.0e6 (default 5.0e6 already quite high)
  • ea_13 = 1.0e5 to 1.0e7 (default 1e6)
  • ea_14 = 0.5 to 1.5 (default 1.0 radians)
  • ea_15 = 0.0 to 0.2 (default 0.1)

Running the model

• Log into a node by using
  • qrsh –q interactive.q
• Start the model experiment from /genie-main by using
  • ./genie_example.job –f configs/genie_eb_go_gs_expt1.config
• You will now get output to the screen and the experiment will take around an hour
• Meanwhile output datasets will be written to /genie-output/genie_eb_go_gs_expt1

Further work

• Repeat the above but create genie_eb_go_gs_expt2.config in which you change EXPID to genie_eb_go_gs_expt2, and set ea_20 = 2.0 (for 2x pre-industrial CO2)
• You can view the ascii output files
  • e.g. /genie-output/genie_eb_go_gs_expt2/embm/spn.airt – this file lists hemispheric mean air temperatures and global maximum and minimum air temperatures and their locations.
    • compare the values between expt1 and expt2 to see the effect of doubling CO2
  • e.g. /genie-output/genie_eb_go_gs_expt2/goldstein/spn.opsit - this file lists maximum and minimum meridional overturning streamfunctions in the Pacific and Atlantic and their locations.
    • compare the values between expt1 and expt2 to see the effect of doubling CO2
• You can look at the netCDF results using e.g. Panoply.