[RegCNET] Time step problem or something else ?

[Dilip Ganguly]

Many thanks Jagadish for your willingness to help.

As you are telling that changing domain boundary, convective scheme or 
increasing resolution may help. But my problem is I have already completed 
a long simulation and all this problem is occurring when there is just a 
small time remaing compared to the total time of simulation.

Can anyone suggest a solution to my problem ?

Thanks

Dilip.

On Thu, 4 Jan 2007, jagadish karmacharya wrote:

> 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. 
  
     ---------------------------------------------------------------------
        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
     ---------------------------------------------------------------------