Hello Letuma,

In my experience your specifications are near the borderline for numerical stability. This means that while the time step will work on many occasions, sometimes it will not. Therefore I suggest reducing the time step to 120 seconds.

The information you give does not specify the convection scheme you use. I have found that use of the Emanuel convection scheme often requires a smaller time step than when one of the other schemes is used. So, if you are using the Emanuel scheme it would be another reason to reduce the time step.

I hope this is helpful for you. Good luck.

Ray Arritt

On 2/11/2012 11:47 PM, Mosuoe Letuma wrote:

Dear All.

May i kindly ask about the CFL Violation error. I am running for Southern Africa Region using RegCM-4.0_clm. The simmulation completed successfully for one month, but failed for 7 months with the CFL Violation error. My regcm.in looks as follows:

/

&dimparam

iy = 132,

jx = 128,

kz = 18,

nsg = 1,

/

&geoparam

iproj = 'NORMER',

ds = 50.0,

ptop = 5.0,

clat = -15.00,

clon = 30.00,

! plat = 30.00,

! plon = 115.00,

! truelatl = 30.0,

! truelath = 60,

/

:

:

/

&timeparam

radfrq = 30.,

abemh = 18.,

abatm = 600.,

dt = 150.,

ibdyfrq = 6,

/

I also run the model for Africa, which was successful for 1990 and 1991, but 1992, 1993 and 1995 gave me the error, CFL Violatio. The regcm.in was:

/

&dimparam

iy = 180,

jx = 184,

kz = 18,

nsg = 1,

/

&geoparam

iproj = 'NORMER',

ds = 50.0,

ptop = 5.0,

clat = 0.00,

clon = 18.00,

/

The timeparam stanza was the same for the both domains. Upto this far, i have not yet got the solutions to the previously posted problems regarding the same error. May anyone help.

Kind Regards,

Letuma

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