[RegCNET] Time step problem or something else ?
Rauscher Sara A
srausche at ictp.it
Mon Jan 8 10:10:07 CET 2007
Hi Dipil,
During a long run this can sometimes happen. Usually I restart (before
the time of the crash) using a shorter time step in regcm.in. When the
simulation moves past the time of the crash, I then stop the simulation
and restart with the original time step. This is a way for dealing with
one or two crashes in a long simulation.
If you are experiencing lots of crashes, this is NOT an appropriate way
to handle it - you should follow Jagadish's suggestions regarding
checking the time step, location and boundaries of the domain, model
resolution, and the physical parameterizations etc. and do further tests
before beginning a long simulation.
Let me know if you require further information.
cheers,
sara
jagadish karmacharya wrote:
> Dear Dipil,
>
> You shouldn't change parameters at the middle of an experiments. My
> suggestion was to make the changes if you are starting new experiments.
>
> Have you checked the ICBC file for that date/month in grads?
>
> One thing you can do is to run new identical simulation begining from
> the 1st date of the month where you are getting problem just to
> check if the problem persist or not. You may also try to restart the
> experiment with different convection scheme just for the purpose of
> checking. Obviously these will not be part of you long simulation.
>
> All the best
>
> Jagadish
>
> */Dilip Ganguly <dganguly at prl.res.in>/* wrote:
>
> Dear Jagadish,
>
> As you are suggesting that changing domain boundary, convective
> scheme,
> increasing resolution etc. might help in avoiding this kind of
> situation.
> But my problem is that I am already in the middle of a long
> simulation and
> this problem due to convective instability is occuring towards the
> end of
> my simulation. At this stage how can I introduce changes which you
> want me
> to try ? Is there any other way to get out of this problem at this
> stage ?
>
> Regards,
>
> Dilip.
>
>
> > Dear Dilip,
> >
> > You have tried all the way down to dt=1 sec but as you have seen
> > decreasing time step doesn't always solve the problem. I generally
> > decrease dt upto 1.5*resolution in km (instead of dt=3*res) to
> check if
> > if overcome the problem.
> > When the problem persists with decreased timestep as well it is
> difficult
> > to figure out a solution.
> >
> > Changing domain boundary, convective scheme, increasing
> resolution may
> > help but if one has already completed long simulation then it
> become a
> > problem. One possibility is that your ICBC or driving data file
> for that
> > month may be corrupt but its less likely.
> >
> > Can anyone give some suggestion?
> >
> > Regards
> > Jagadish
> >
> >
> > Dilip Ganguly wrote: Dear all,
> >
> > I am facing problem in running RegCM3. The program hangs and
> does not seem
> > to work after a particular time and I am getting messages on the
> screen
> > like the following.
> >
> > BATS variables written at 2004120121 180.000000000000
> > at day = 396.8762, ktau = 210200 : 1st, 2nd time deriv of ps =
> > 0.10915E-02 0.49528E-05, no. of points w/convection = 81
> > at day = 396.8849, ktau = 210250 : 1st, 2nd time deriv of ps =
> > 0.97549E-03 0.41641E-05, no. of points w/convection = 71
> > at day = 396.8936, ktau = 210300 : 1st, 2nd time deriv of ps =
> > NaN NaN , no. of points w/convection = 0
> >
> >
> -------------------------------------------------------------------------
> >
> > It do not know if it is due to improper choice of time steps. I have
> > restarted the program several times with lower and lower values
> of time
> > step dt but every time the program hangs around a certain period
> of time
> > and not able to cross this period. I have tried with numerous
> combinations
> > of gradually decreasing time steps. Some are given below.
> >
> > radfrq= 30 30 30 30 15 15 15
> > abemh = 18 18 18 18 9 9 9
> > abatm = 300 120 90 45 30 9 3
> > dt = 100 60 30 15 10 3 1
> >
> > But none of them worked. Everytime it shows the same problem
> possibly due
> > to convective instability as told by Jagadish. I am using a 90 km
> > horizontal resolution in my simulation.
> >
> > Can anyone suggest a way to solve this problem ?
> >
> > Thanking you in advance.
> >
> > Dilip.
> >
> >
> ---------------------------------------------------------------------
> > DILIP GANGULY
> > Postdoctoral Fellow
> > Space And Atmospheric Sciences Division
> > Physical Research Laboratory
> > Ahmedabad 380009
> > Gujarat, India
> > Phone: +91 79 26314558 (Laboratory)
> > +91 79 26300505 (Hostel)
> > Fax: +91 79 26314659
> > Alternate Email: ganguly.dilip at gmail.com
> > Visit me at http://www.prl.res.in/~dganguly
> >
> ---------------------------------------------------------------------
> >
> >
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>
> --
> Dilip Ganguly
> Postdoctoral Fellow
> Space and Atmospheric Sciences Division
> Physical Research Laboratory
> Navrangpura
> Ahmedabad-380009
> Gujarat, India
> Phone:+91 79 26314558, Fax: +91 79 26314659
> Alternate Email: ganguly.dilip at gmail.com
> visit me at: http://www.prl.res.in/~dganguly
>
>
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--
Dr. Sara A. Rauscher
Earth System Physics Section
The Abdus Salam International Centre for Theoretical Physics
Strada Costiera 11
34014 Trieste ITALY
ph: +39 040 2240 225 fax: +39 040 2240 449
email: srausche at ictp.it
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