[RegCNET] Time step problem or something else ?

[Dilip Ganguly]

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 <dganguly at prl.res.in> 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