[RegCNET] Re: Sigma Levels

[moetasim]

Hi Jeremy , Bi n All,

Neil and I are trying to figure out the reason why he has floating point 
exception (FPE) while running RegCM with his modified sigma levels. What we 
got finally is that regcm works fine with his modified levels at a 
relatively smaller domain than the one which ends up with FPE. I had 
actually tried to run regcm with his modified levels at a smaller domain and 
found that it works fine. Same kind of result he got when he ran the model 
with his modified levels but, smaller domain. I can't really say anything 
with confidence that why is it happening? He has domain size = 74 x 136 x 23 
for the simulation which ends up with FPE. The same domain works fine if he 
runs the model without modifying sigma levels. 

Is it happening because his modified levels are more concentrated in low 
level (say in PBL) which is making it more computationally tough for PBL 
model or what else? There is no reason other than computationally 
incompatibility to end up with a FPE for larger domain + modified sigma 
levels, if model works fine for both small domain + modified sigma levels, 
and larger domain + default sigma levels (its my point of view).

(I have attached the gradual progress to this conclusion here under) 

MOet


Quoting Neil Davis <nndavis at unity.ncsu.edu>:

> I tried running the 50 X50X23 and that seems to be working, it has run 
> through the first month already so I am assuming that that works.  I am 
> just wondering why the default 23 sigma levels would run on my large 
> domain, when the proposed ones do not.  Is there something with the 
> stacking in the lower levels that adds computer memory or something that 
> I am missing. 
> 
> Thank you again for all your help on this problem,
> Neil Davis

Quoting moetasim <mashfaq at purdue.edu>:

> To be on safe side just make a check with small domain like 50 x 50 x 23!
> 
> 
> 
> 
> 
> 
> Quoting Neil Davis <nndavis at unity.ncsu.edu>:
> 
> > How much of a decrease would you suggest?  I did run the identical 
> > domain with the default 23 vertical levels.  I am running the model on 
> > an IBM blade cluster running redhat linux.  Glad to hear that the model 
> > is running somewhere with my proposed sigma levels.  I will try your 
> > suggestion of a smaller domain and see if that fixes it. 
> > Neil

Quoting moetasim <mashfaq at purdue.edu>:

> Hi,
> I have an early conclusion for your problem, now. It seems that increase 
in 
> vertical resolution and considerably large domain (that you have for your 
> experiment) is creating the crash. You may prove me right/wrong by just 
> decreasing your domain size and running the model. I had read previously 
that
> 
> you mentioned RegCM working fine with its default defined 23 sigma levels.
> Did 
> you run that experiment with same domain size as its in this case of your 
> modified sigma levels experiment.
> 
> Once you are done with with your problem, I will post the final answer at 
> RegCNET. By the way, model is running without any problem at my end with 
your
> 
> proposed sigma levels. Which machine do you have for running RegCM?
> 
> MOet
> 
> 
> 
> Quoting Neil Davis <nndavis at unity.ncsu.edu>:
>
Quoting moetasim <mashfaq at purdue.edu>:

> I have started running RegcM with your defined 23 sigma levels..At the 
moment
> it 
> running..lets see hw it goes..
>  
Quoting moetasim <mashfaq at purdue.edu>:

> Yeah just make sure that every thing is fine for 3D variables written in 
ICBC
> 
> files.
>  
Quoting Neil Davis <nndavis at unity.ncsu.edu>:

> I have attached the output and the error log of the model run.  This 
> time it didn't seem to even start a few days.  I will try your other 
> suggestions now, although what did you mean by check icbc at different 
> sigma levels, just look at the ICBC files and see if the values look 
> reasonable? 
> 
> Thanks again for your help
> Neil
> 
> 
>

Quoting moetasim <mashfaq at purdue.edu>:

> Ok, can you send me the output that you get after running regcm.x (start 
to 
> the point where FPE occurs).
> 
> and for the time being:
> 
> 1) check icbc at differnt sigma levels. If everything is fine there and 
tell
> 
> me.
> 
> 2)Also, try to run the model with reduced time step and let me know what 
> happens.
> But before this send the ./regcm.x output.
> 
> MOet  
> 
> 
> Quoting Neil Davis <nndavis at unity.ncsu.edu>:
> 
> > Sorry, the exception takes place when running the model.  It goes a few 
> > time steps then the error occurs.  ICBC and Terrain seem to have no 
> > errors when I run them.
> > 
> > 
> 
> 
> -- 
>

Quoting moetasim <mashfaq at purdue.edu>:

> But you didnt tell me at what step yuo have floating point exception?
> Terrain, 
> ICBC or while executing model?


Quoting Neil Davis <nndavis at unity.ncsu.edu>:

> I just changed in terrain.f the lines 1423 to 1448 to this
> else if(kz.eq.23) then                  ! MM5V3
>          sigma(1) = 0.0
>          sigma(2) = 0.05
>          sigma(3) = 0.1
>          sigma(4) = 0.16
>          sigma(5) = 0.23
>          sigma(6) = 0.31
>          sigma(7) = 0.39
>          sigma(8) = 0.47
>          sigma(9) = 0.55
>          sigma(10)= 0.61
>          sigma(11)= 0.66
>          sigma(12)= 0.69
>          sigma(13)= 0.72
>          sigma(14)= 0.75
>          sigma(15)= 0.78
>          sigma(16)= 0.81
>          sigma(17)= 0.84
>          sigma(18)= 0.87
>          sigma(19)= 0.9
>          sigma(20)= 0.93
>          sigma(21)= 0.96
>          sigma(22)= 0.98
>          sigma(23)= 0.99
>          sigma(24)= 1.0
>       else
> 
> moetasim wrote:
> > let me have a look at your changes.
> >
> > MOet
> >
> > On Tue, 25 Oct 2005 09:36:08 -0400, Neil Davis wrote
> >   
> >> I am working with RegCM over tropical Africa and want to adjust the 
> >> sigma levels in the 23 level setting so that there are more levels 
> >> below 3000 m than in its current set up.  I have been able to run 
> >> the model with the default 23 sigma levels but when I try to change 
> >> it to increased levels in the lower atmosphere I get a floating 
> >> point exception.  I was wondering if it is at all possible to change 
> >> the sigma levels from the default, and if it is possible what could 
> >> be causing the floating point exception.  I can post my adjusted 
> >> sigma levels if that will help.
> >>
> >> Neil Davis
> >> NCSU climate modeling lab
> >>