Perturbation for CAM4 ensemble runs

[sirajkhan78@gmail_com]

Hi all,

I am wondering if some one can help me to generate ensemble runs using CAM4. I run the model from 1980 to 2010 with prescribed SST and now I want to make 5 or 6 more runs of CAM4 with the same setting but with some perturbation. I know there is "pertim" option in CAM for the perturbation in initial conditions (ICs) but my control runs span around 20 years and therefore perturbation in the ICs are not useful for me. I want to perturbed SST or sea (boundary condition) to make ensemble runs I guess or any other way ? I have heard about AMIP runs of ensemble CAM4 but there is no information on Internet about how these ensemble members are generated.

Also as I am making ensembles, I switched off (using "empty_htapes=.true" option) many output variables in CAM output. I only need some variables of CAM in output, whereas model is generating output for land and ice model as well. Is there any way to switch off output of "clm" and "ice" models in CAM4 output.

Siraj

 

[jedwards]

I believe that to apply a perturbation to the sst's you would edit file docn_comp_mod.F90 and apply a purturbation to field o2x%rAttr(kt ,n) 

case('SSTDATA')
      lsize = mct_avect_lsize(o2x)
      do n = 1,lsize
         o2x%rAttr(kt   ,n) = o2x%rAttr(kt,n) + TkFrz<br /><br /><br />I'm not sure I understand your comment about the CAM pertlim option.  I suspect that it's adequate for your needs as perturbations in initial conditions <br />continue to grow over the course of the runs.   <br /><br />in newer versions of the model you can turn off clm and cice output using:<br /><br />echo "hist_empty_htapes = .true." >> user_nl_clm<br />echo "histfreq = 'x','x','x','x','x'" >> user_nl_cice<br /><br /><br />