[MITgcm-support] model crashing & time step issues

[Neil Patel]

Using the 4° resolution tutorial_global_oce_latlon as a starting point, I modified the input files to a higher, 2° resolution but similar values to the original. I changed the dxSpacing and dySpacing to 2 in input/data, and the number of grid cells to 180 and 80 for x and y (one processor and one thread configuration) respectively in code/SIZE.h. When I ran it I got this error:

terra tutorial_global_oce_latlon_newgrid/input> ../build/mitgcmuv > output.txt
SOLUTION IS HEADING OUT OF BOUNDS: tMin,tMax= -3.088E+03  1.119E+04
 exceeds allowed range (monSolutionMaxRange=  1.000E+03)
MON_SOLUTION: STOPPING CALCULATION at Iter=         6
S/R ALL_PROC_DIE: ending the run
ABNORMAL END: S/R MON_SOLUTION, stops due to EXTREME Pot.Temp

Mitgcm was able to run for 8 days (I told input/data to create an output file for each day) without crashing. I viewed the last temperature output file for day 8 and it appeared normal (sea surface temperatures maxed out around 30°C). Why was the simulation able to do 8 days without much error and then suddenly diverge in one day? Or are the problems being created in another parameter?

Then, I changed the length of all the time steps in input/data to 1/4 of the original. This time, it ran out to 20 days, then crashed in the same way as previously. Next, I changed the size of all the time steps in input/dat to 1/10 of the original. Then, it ran normally out to 200 days (which is when I set the simulation to end).

What's the reason for the sudden crashes? Is there a way to predict what time step is best for the simulation?

Thanks,

Neil