[RegCNET] Time step problem or something else ?

[Oliver.Tomingas at ut.ee]

   Dear Dilip,

   If 90 km is not crucial for your experiment, try changing model
   resolution, not only time step. It worked for me (I was
   getting computational instability messages for 20 km
   resolution run after about one year simulation with various
   time steps). I use 25 km resolution now.
   Also, time step 100 s for 90 km resolution seems
   too small to me.
   I guess dt between 270 and 200 is more reasonable.

   Oliver

On Thu, 4 Jan 2007, 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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>
>
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