OpenIFS model known issues

Wave model can crash if restarts and wave model output are enabled

There is a known bug with  OpenIFS 38r1 and 40r1 (all versions). The bug causes the wave model to crash under specific circumstances. Only if (i) wave model output is enabled; (ii) model restarts are enabled; (iii) low resolutions are used such that the wave model needs to take multiple sub-timesteps for each atmospheric model timestep.

For a solution to this issue, please see this OpenIFS Forum post.

Restart file generation can suffer reproducibility problems

Occasional random bit-flips can occur when the model writes restart files in both OpenIFS 38r1 and 40r1. This means that two identical runs, which are restarted multiple times, may not give the same results as each other. Note this does not affect a model run that does not need a restart, regardless of whether or not the model writes restart files as it runs.

This has been logged as a bug on our internal OpenIFS issue tracking. A fix is not likely soon, but when there is more information it will be posted. here. The OpenIFS internal issue is OIFS-305 - Getting issue details... STATUS .

GSTATS counter overflow from total number of timesteps

In cases of very long integrations the OpenIFS model can fail because of the overflow in some integer counters due to the total number of timesteps.

The GSTATS statistics for transforms can only be called NCALLS(KNUM) times. This variable is defined as:

INTEGER(KIND=JPIM) :: NCALLS(0:JPMAXSTAT)

which means that it is limited to 2³¹-1 = 2147483647 calls of transformations or any other package for which the GSTATS statistics are used.  Adding one to this maximum number turns this counter to be -2147483647 which then causes the model to crash.

The error is something like:

KNUM,KSWITCH,IMOD,NCALLS(KNUM) 805,  0,  -1,  -2147483647 ABORT!  408 GSTATS
 MPL_ABORT: CALLED FROM PROCESSOR    408 THRD     

The solution in this case is to switch off the GSTATS statistics, or (preferably) shorten the length of integration between restarts.

Contact openifs-support@ecmwf.int for assistance or further information.