[MITgcm-support] z coordinate

Baylor Fox-Kemper baylor at MIT.EDU
Tue Jan 2 09:36:50 EST 2007

Hi Rima,
   The MITgcm is not accurate when you change the delZ so rapidly.   
You are much better off using the 20 levels, if you can afford to run  
it that way.  If not, you can make a few levels of delz=30m, then  
gradually increase until you reach bottom.  The grid size shouldn't  
increase too rapidly from level to level, approximately 20% at most.   
This will be even more important in nonhydrostatic mode.

On Jan 2, 2007, at 7:09 AM, Riema Rachmayani wrote:

> dear MITgcm,
> first, now i have problem with z coordinate, in my case i have  
> water depth =1000 m, divided become 2 layers, 1st layer is 30 m,  
> 2nd layer is 970m, when describe it in data file
> delZ=30.0,970.0, right?? but i have bad result..from the  
> visualisation of temperature distribution it just look the top of  
> sill, not entire water depth, and when i describe it into 20 layers  
> for each 50m in data file delZ=20*50.0, i have good result for the  
> visualisation, i can see entire water depth, larger number of delz  
> is better?? or i forgot something to change beside change Nr in  
> code/SIZE.h??
> second, i've done internal wave verification in nonhydrostatic for  
> MITgcm case with bathyfile =topog.slope, i can see interface  
> profile disturbed by the effect of nonhydrostatic, barotropic tidal  
> and bathy slope, but when i change bathyfile longer, i saw no same  
> effect again, it is matter of initial value of Tref, open  
> boundaries right?? any steps i should do about boundaries or  
> initial value?? what about when i'll use East open boundary, West  
> open boundary??change in obcs_calc.F??
> thank you,
> regards
> rima
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