(lats pole to eq)
|Grid type||Resolution at equator|
(npts at eq. / spacing)
|Wave model |
|Tco1279||O1280||cubic oct / _4||5136 / 8km / 0.070o||0.125o||7.5||Operational forecast resolution (43r3)|
|Tl1279||N640||linear reduced / l_2||2560 / 16km / 0.141o||0.25o||10||Operational forecast resolution (40r1)|
|N512||linear reduced / l_2||2048 / 20km / 0.176o||0.25o||10||-|
|Tco799||O800||cubic oct / _4||3216 / 12.5km / 0.112o||0.125o||12||-|
|Tl799||N400||linear reduced / l_2||1600 / 25km / 0.225o||0.36o||12||-|
|Tco639||O640||cubic oct / _4||2576 / 16km / 0.140o||0.25o||12||Operational ensemble resolution (43r3)|
|Tl639||N320||linear reduced / l_2||1280 / 31km / 0.281o||0.36o||15||ERA-5 high resolution|
|Tl511||N256||linear reduced / l_2||1024 / 39km / 0.352o||0.50o||15||-|
|Tco399||O400||cubic oct / _4||1616 / 25km / 0.223o||0.36o||15||-|
|Tl399||N200||linear reduced / l_2||800 / 50km / 0.45o||1.0o||20||Operational ensemble resolution (40r1)|
|Tco319||O320||cubic oct / _4||1296 / 31km / 0.278o||0.36o||15||Seasonal system 5|
|Tl319||N160||linear reduced / l_2||640 / 63km / 0.563o||1.0o||20||ERA-5 ensemble|
|Tco255||O256||cubic oct / _4||1040 / 39km / 0.346o||0.50o||20||-|
|Tl255||N128||linear reduced / l_2||512 / 78km / 0.703o||1.0o||45||ERA-Interim; Seasonal system 4|
|quadratic reduced / _2||640 / 63km / 0.563o||1.0o||20||-|
|Tco199||O200||cubic oct / _4||816 / 49km / 0.44o||1.0o||20||-|
|Tco159||O160||cubic oct / _4||656 / 61km / 0.55o||1.0o||20||-|
|Tl159||N80||linear reduced / l_2||320 / 125km / 1.125o||1.5o||60||ERA-40|
|Tq106||F80||quadratic reduced / _2||320 / 125km / 1.125o||1.5o||60||-|
|Tco95||O96||cubic oct / _4||400 / 100km / 0.9o||1.0o||30||-|
|Tl95||N48||linear reduced / l_2||192 / 209km / 1.875o||3.0o||60||-|
|Tq63||F48||quadratic reduced / _2||192 / 209km / 1.875o||3.0o||60||-|
|Tq42||F32||quadratic regular / _full||128 / 313km / 2.813o||3.0o||30||Development/testing only|
|Tq21||F16||quadratic regular / _full||64 / 626km / 5.625o||3.0o||30||Development/testing only|
- Grid type suffix refers to the file suffix used at the end of filenames for the OpenIFS/IFS climatology files. It is also used as an argument to the 'gaussgr' command, see 4.5 OpenIFS: Grid tools.
- The 'cubic' grid rather than 'cubic octahedral' is not listed here as it's infrequently used, the suffix for these files is '_3'.
- T21 and T42 use the Eulerian dynamical core and a regular Gaussian grid.
- Tco denotes cubic octahedral grid, Tl denotes a linear grid, Tq denotes a quadratic grid.
- Other resolutions not listed here may be provided with the OpenIFS climatology files.
Regarding the recommended timestep, what is this based on? I'm running TCO159 with 60 minute timestep without any semi-Lagrangian trajectories going underground. Recommended are 20 minutes. Am I in the clear as long as the model is stable, or can I expect degradation of results by coming close to the limit?
I would ask your boss since he wrote a nice paper about it a while back. Jung et al. doi: 10.1175/JCLI-D-11-00265.1. They mention that TL159 (lin trunc) with 60min time step has lots of biases in tropics, but reducing time step to 15 min (as TL511) improves this a lot. Also, I accidentally ran TL511 with 60 min time step once. So I think OpenIFS is very stable numerically and your choice of time step is boils down to computational cost vs. quality of forecasts.
The values in the table above were taken from 'prepIFS' that creates the experiments and are the recommended defaults. Joakim is correct, the model's semi-Lagrangian dynamics can remain stable but will become less accurate as the timestep is increased. You should always validate the model results.
Interesting, some of these values seem to be quite conservative. E.g. recommended maximum for TCO199 is 12 minutes but in Primavera ECMWF used 30 minutes: 10.5194/gmd-11-3681-2018
Long timesteps are one of the main advantages of OpenIFS, so I think you are selling yourself a bit short with these.
I double checked the value for Tco199 and 12 mins is what our prepIFS system would set it to. However, that looks like a mistake to me as the timestep is 20mins for the next highest resolution. The timestep should go with the physical grid resolution (O200), the equivalent to Tco199 would be Tl399 (N200), which again has a 20min timestep. I will make the change to the table and leave these comments here for interest.
Thanks for pointing that out!
Hello, can TL191 be added to this table? It's used in the CAMS GHG o-suite (becoming officially operational in 48r1).