CCLM failed with error code 1004 – in #9: CCLM

in #9: CCLM

<p> Dear Delei, </p> <p> a collegue of mine had also cases where decreasing the timestep helped... </p> <p> if you test for example dt = 10,15,20,30 you could compare at which time (not steps, but time) the first NaN ocurr and if increasing or decreasing makes it better/worse. <br/> (oh and does the CFL-criterion still get violated with other timesteps?) </p> <p> But overall since it happens in the first minute, I guess it won´t help... </p> <p> I have had several cases when we had no problem running 15, and 5 km resolution, but with finer resolution (nested inside) sometimes the simulation never became stable enough no matter the timestep. And we didn´t spend more time on it, but just skipped those. </p> <p> -------- </p> <p> in your case I guess (4) is best to trace back the Problem, since you know now a location, where it is happening. (how do other varibles look/behave there just before it gets NaN?) </p> <p> I had one case, where there was a very steep mountain ( &gt;500m height increase from one grid point to the next ) where wind speeds an temperature would get unrealistic values before the crash. </p> <p> Another case was where single grid points just had very unrealistic cold temperatures, that could not be fixed and normaly did not cause a problem. But sometimes the temperature would drop even lower and than NaN would spread from this gridpoints. </p> <p> Quick idea, if the point is not in the middle but near the border of your domain: just reduce the domainsize to exclude the point. I think you just have to change [ startlon_tot, startlat_tot, ie_tot, je_tot] so it should be no effort? </p> <p> if it works afterwards, you may be more certain that the problem is really at that location, and not a more generall problem that occurs first at that point, but would also happen 1-2 minutes later at other points. </p> <p> Cheers <br/> Rolf </p>

  @rolfzentek in #0b2d088

<p> Dear Delei, </p> <p> a collegue of mine had also cases where decreasing the timestep helped... </p> <p> if you test for example dt = 10,15,20,30 you could compare at which time (not steps, but time) the first NaN ocurr and if increasing or decreasing makes it better/worse. <br/> (oh and does the CFL-criterion still get violated with other timesteps?) </p> <p> But overall since it happens in the first minute, I guess it won´t help... </p> <p> I have had several cases when we had no problem running 15, and 5 km resolution, but with finer resolution (nested inside) sometimes the simulation never became stable enough no matter the timestep. And we didn´t spend more time on it, but just skipped those. </p> <p> -------- </p> <p> in your case I guess (4) is best to trace back the Problem, since you know now a location, where it is happening. (how do other varibles look/behave there just before it gets NaN?) </p> <p> I had one case, where there was a very steep mountain ( &gt;500m height increase from one grid point to the next ) where wind speeds an temperature would get unrealistic values before the crash. </p> <p> Another case was where single grid points just had very unrealistic cold temperatures, that could not be fixed and normaly did not cause a problem. But sometimes the temperature would drop even lower and than NaN would spread from this gridpoints. </p> <p> Quick idea, if the point is not in the middle but near the border of your domain: just reduce the domainsize to exclude the point. I think you just have to change [ startlon_tot, startlat_tot, ie_tot, je_tot] so it should be no effort? </p> <p> if it works afterwards, you may be more certain that the problem is really at that location, and not a more generall problem that occurs first at that point, but would also happen 1-2 minutes later at other points. </p> <p> Cheers <br/> Rolf </p>
RZ replied

Dear Delei,

a collegue of mine had also cases where decreasing the timestep helped...

if you test for example dt = 10,15,20,30 you could compare at which time (not steps, but time) the first NaN ocurr and if increasing or decreasing makes it better/worse.
(oh and does the CFL-criterion still get violated with other timesteps?)

But overall since it happens in the first minute, I guess it won´t help...

I have had several cases when we had no problem running 15, and 5 km resolution, but with finer resolution (nested inside) sometimes the simulation never became stable enough no matter the timestep. And we didn´t spend more time on it, but just skipped those.

--------

in your case I guess (4) is best to trace back the Problem, since you know now a location, where it is happening. (how do other varibles look/behave there just before it gets NaN?)

I had one case, where there was a very steep mountain ( >500m height increase from one grid point to the next ) where wind speeds an temperature would get unrealistic values before the crash.

Another case was where single grid points just had very unrealistic cold temperatures, that could not be fixed and normaly did not cause a problem. But sometimes the temperature would drop even lower and than NaN would spread from this gridpoints.

Quick idea, if the point is not in the middle but near the border of your domain: just reduce the domainsize to exclude the point. I think you just have to change [ startlon_tot, startlat_tot, ie_tot, je_tot] so it should be no effort?

if it works afterwards, you may be more certain that the problem is really at that location, and not a more generall problem that occurs first at that point, but would also happen 1-2 minutes later at other points.

Cheers
Rolf

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