[cam-users] Solar forcing

[Peter Langen]

  Hi CCM (and CAM) users,

I'm running CCM366 with aqua planet/slab ocean lower boundary 
conditions. I don't want an annual cycle in my experiments so I've just 
set ECCEN=OBLIQ=0. However, under these conditions the solar flux at the 
poles vanishes and I get an ever increasing equator-to-pole temperature 
gradient. A proper way of fixing this is to use an annual mean diurnal 
cycle corresponding to the pattern one obtains when averaging the 
insolation at, say, 00:00 GMT each day of a year in every point. I 
haven't made such at data set yet, but I don't think this will be the 
problem.

The problem is how to get CCM366 to use this insolation. Also, it isn't 
quite clear what to do with the zenith angle used both in the radiation 
code and in the albedo calculations, since our artificial insolation 
does not correspond to any physical zenith angle.

Has anybody tried working with the CCM without an annual cycle?

One other question (which I've seen also in the ccm-users archive - 
without an answer): When running at T21 resolution the User's Guide says 
to change the namelist variables DTIME, DIF2 and DIF4 from their default 
T42 values, but the example script only changes DTIME. What about DIF2 
and DIF4? In the CAM User's Guide DIF2 is left unchanged relative to the 
T42 case while DIF4 is doubled. Until now I've just done the same with 
CCM366, but is this the right thing to do?

Thanks
Peter Langen

-- 
Peter Langen
Niels Bohr Institute for Astronomy, Physics and Geophysics
Geophysical Department
University of Copenhagen