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Domain & resolution
First you should decide if your upon the final(!) simulation (see "Cascading" below) should be on a regional or a global grid and at which domain and resolution you want to run. For this it is important to know that:
- the more grid points a grid has , => the more cores are needed and
- the smaller higher the resolution and with that => the shorter the model timestep => the longer the simulation will take.the runtime of the simulation
Have a look at the following wiki about how to set up a model grid: Set up a model grid
Number of points
Topology (MPI & OpenMP)
Resolution → timestep
The relation between the horizontal resolution and the model timestep is linear. Here are some examples:
| Resolution [degree] | Resolution [km] | model timestep [sec] | For GY grid |
|---|---|---|---|
| 0.009° | ~1 km | 30 s | |
| 0.0225° | ~2.5 km | 60 s | |
| 0.036° | ~4 km | 90 s | |
| 0.11° | ~12 km | 300 s | |
| ~25 km | 720 s | Grd_nj = 417 | |
| ~55 km | 1800 s | Grd_nj = 171 |
Resolution → timestep → radiation timestep
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Cascadeing
Spectral nudging
Period
Greenhouse gases / Scenario
Initial conditions
Driving data
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Lake scheme (non, FLake, CSLM)
Urbain scheme (non, TEB)
Radiation
Roughness length
Limit ice /snow
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Size of output files (monthly/daily/hourly/...)
Submission
Account
Wall clock time
On the clusters of the Alliance are different queues for jobs requesting different amounts of walltime as well as memory. To find out which type of queues exist on the cluster you want to run on check out the following wiki of the Alliance: Job_scheduling_policies
In the config file 'configexp.cfg' set 'BACKEND_time_mod' to the amount of seconds you want to request for a single job(1) - not for the whole simulation which can consist of multiple jobs.
In general, the shorter the requested time the shorter the queued time. Therefore, you want to request as little time as possible for a job. However, runtimes on clusters of the Alliance can vary by a lot, normally between -15 % to + 20 % of the average runtime. Hence, one should request runtimes that are about 25 % larger than the average expected runtime.