[RegCNET] Time step problem or something else ?

[jagadish karmacharya]

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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