[RegCNET] Nan error during model run-Common problem

Fri Jan 29 09:54:12 CET 2010

 Dear Satyaban
  Please don't give up, you will be happy if the model run properly..but
you need some time and more triels..all of us are absent of your system,
and we do our best to guess where the errors of your system coming from?
 again, recheck the source of boundary conditions you have
 sometime, you don' have the complete files..also, have you checked the
system with only one processor.

regards

>
> Dear Sara and All,
> Thanks for your mail and detail information about the Nan error in the
> RegCM3 model run.
> As this Nan error is a common problem in RegCM, I have some point in
> continuation with this discussion.
> Mainly, even though model is encountering Nan error during the integration
> still it proceeds up to completion of the integration. For long simulation
> people don't monitor continuously whether model running smoothly or there
> is a chance of nan error.
> Sometimes, people see that they have completed their simulation
> successfully but at the time of analyse their model output they realize
> that there is Nan error and the model output is no use.
> So they need to start or restart the simulation again.
> In my opinion it will better if there will be facility such that, In case
> there is a Nan error during the run it should come out immediately and
> stop the integration automatically without proceed further.
> In this way we can save lot of time.
>
> Thanking you.
>
> Best regards
> Satyaban
>
> On Thu, 28 Jan 2010 22:24:41 +0530  wrote
>>Dear Dwijenra,
>
> This is the most common question on the list (in fact, it was answered
> the other day). Everyone, please read the user's guide! It contains
> valuable information that will help you run your simulations.
> http://users.ictp.it/RegCNET/regcm.pdf
>
> The model is sensitive to the time step used. The first rule of thumb is
> to use 3 times the horizontal grid spacing. In your case, 60 km, so 180
> is the best to start with. However, in cases of steep topography you may
> need to decrease this time step. You might want to try 150, for example.
>
> If you are doing a long simulation, and this just happens once or twice,
> you can work around this. Set the time step to a lower value, restart
> the model to a point before where it blew up, and then after this point,
> stop the model, put the time step back to its original value, and
> restart the model. So for example, if my model had died on January 5th,
> I would probably restart at the beginning of January, do that month at a
> lower time step, and then continue the simulation in February at the
> original time step if that's been working. Note that this is acceptable
> to do once or twice in a long simulation (like > 5 years), but if it
> happens more often, you should restart the simulation from the beginning
> at a shorter time step.
>
> In the regcm user guide, there is a table that gives suggestions (these
> are just suggestions) for time steps for different grid spacing (Table
> 12, page 40):
> Table 12: Time steps with different resolutions:
>
> dx(km) dt(sec) abatm(sec) abemh(hr) radfrq(min)
> 10 30 90 18 30
> 20 60 120 18 30
> 30 100 300 18 30
> 45 150 300 18 30
> 50 150 450 18 30
> 60 200 600 18 30
> 90 225 900 18 30
>
> There is discussion of how to set the time step on page 35 in the user's
> guide.
> cheers
> sara
>
>
> d d wrote:
>> Dear RegCNET Users,
>>
>> I am having similar problem as Dr. Satyaban getting the NaN error
>> while running RegCM for 6 months simulation. The ICBC files are OK
>> when i checked them on grads. The Model can run successfully upto 4
>> months and after that it encounters NaN error for last two months.
>> I had tried to restart the simulation but still the same
>> domain.param configuration
>> Idate1=1997010100 start day of simulation
>> Idate2=1997063000 End day of simulation
>> ds = 60km
>>
>> regcm.in  configuration
>> Idate0=1997010100
>> Idate1=1997010100
>> Idate2=1997063000
>> dt=180
>> radfrq=30
>> abemh=18
>> abatm=540
>>
>> please kindly suggests whar might be the problem
>>
>> Best regards
>> Dwijendra
>>
>> ------------------------------------------------------------------------
>>
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>
>
> --
> Sara A. Rauscher
> T-3 Fluid Dynamics
> MS B216
> Los Alamos National Lab
> Los Alamos, NM 87545 USA
> (505) 606-0512
>
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>
> -------------------------------------------------------------------------------
> Dr. Satyaban Bishoyi Ratna
> Computational Atmospheric Sciences Team
> Scientific & Engineering Computing Group
> Centre for Development of Advanced Computing (C-DAC)
> Pune University Campus, Ganeshkhind
> Pune - 411 007, Maharashtra, India
> E-mail: satyabanb at cdac.in
> Tel (O): +91-020-2570 4226,  (Cell): +91-094223 56326
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All the best
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