[RegCNET] Re: Sigma Levels
Neil Davis
nndavis at unity.ncsu.edu
Fri Oct 28 14:40:09 CEST 2005
I tried this suggestion by changing the timesteps to those listed in the
manual as being good for a dx of 50 km, So I changed dt from 200 to 150
and abatm from 600 to 450 and now the job is running on the larger
domain. Thanks everyone for the suggestions and help. I am wondering
if there is an intermediate change that I could attempt however just to
save some computational time. I wasn't sure if the timestep values had
to be set to certain values or if I could change them some as long as
abatm is 3 tims as large as dt.
Neil Davis
Solmon Fabien wrote:
>
> Hi Moet !
>
> Did you try to play also with the time step on the big domain ? the
> vertical advection is sensitive to sigma level change, I would guess
> that if you have a high vertical velocity in a part of the domain you
> need a smaller time step if you reduce the grid step .... cheers
>
> fabien
> moetasim wrote:
>
>> 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
>>>>>
>>>>>
>>
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