Section | |||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
...
Code changes
There is a small error in OpenIFS 38r1 in the code that sets the SST for the 3KW1 case of Neale & Hoskins. This code incorrectly sets the latitudinal width to 30o instead of 60o.
This error is corrected in later versions of OpenIFS.
Expand | ||||
---|---|---|---|---|
| ||||
The required code changes are small. In the file: src/ifs/phys_ec/gp_sstaqua.F90, find the lines 233:238:
The use of RPHID needs to be corrected to 60o:
|
Configuration
Configuring OpenIFS for an aqua-planet simulation requires appropriate changes to:
...
- Namelists: to enable the idealized configuration and initial fields
- Initial files: to set orography & land-sea-mask.
In the sections below, we walk through the namelist options explaining how to configure the aqua-planet.
Dynamical core and SST
The model namelist NAMDYNCORE
controls the configuration for the model's dynamical coreidealized cases, including the aqua-planet.
To enable the aqua-planet edit the fort.4
file (containing the input model namelist) and make sure the settings are as below. You may find this namelist is blank in your file as it does not need altering for normal forecasts, in which case add the following:
Code Block | ||
---|---|---|
| ||
&NAMDYNCORE LDYNCORE=true, ! switches on idealized planet configurations. LAQUA=true, ! switches on idealized aqua planet. MSSTSCHEME=1, ! controls SST choice for aquaplanet following Neale & Hoskins (2000a) (see ifs/module/yomdyncore.F90 for more details). ! 1 = Control; 2 = Peaked; 3 = Flat; 4 = Qobs; 5 = Control5N; 6 = 1KEQ, chi=1.0; ! 7 = 3KEQ, chi=3.0, width=15 deg; 8 = 3KW1, chi=3.0, width=30 deg; 9 = const. SST / |
The SST modifications can be further changed using the variables defined in ifs/phys_ec/gp_sstaqua.F90
:
Code Block | ||
---|---|---|
| ||
RLAMBDA0 : Longitude of maximum SST anomaly RLAMBDAD, RPHID: Half width in long/lat of SST anomaly RCHI : Maximum magnitude of SST anomaly |
For more details of the SST configuration, see: ifs/phys_ec/gp_sstaqua.F90
. Modifications to the SST distributions can be made in this routine.
Mass conservation
and refer to the Neale & Hoskins (2001) publication.
If idealized initial states are used (see below) rather than real initial fields, it can be useful to introduce some initial noise into the vorticity field. For starting from analysed fields this is not needed:
Code Block | ||
---|---|---|
| ||
&NAMDYNCORE
NOISEVOR=1, ! if 1 add initial noise in vorticity
|
Mass conservation
Enable mass conservation correction Ensure that the mass conservation correction is enabled to prevent mass drifting in long integrations.
Edit namelist NAMDYN in the fort.4 file and add (or change) this variable:
Code Block | ||
---|---|---|
| ||
&NAMDYN
LMASCOR=true, ! if true, apply mass correction.
/ |
Edit namelist NAMCT0 in fort.4 to set the mass correction frequency:
Code Block | ||
---|---|---|
| ||
&NAMCT0 NFRMASSCON=24, ! frequency of mass conversation fixups (time-steps) |
Model physics
Aqua-planet simulations normally use the full model physics. By setting LEPHYS=false
, the model would run an aqua-planet with all the physics switched off.
Ozone
For aqua-planet simulations the prognostic ozone scheme and transport of ozone should be disabled using these logicals in their namelists:
Code Block | ||
---|---|---|
| ||
&NAMGFL
YO3_NL%LGP=false, ! turns off transport of prognostic ozone
&NAEPHY
LEO3CH=false, ! turns off prognostic ozone & uses climatological ozone instead |
Physics namelist
The physics namelist NAEPHY
and no changes are necessary in the NAEPHY namelist. It is included here for completeness.
If necessary edit the fort.4 file (containing the input model namelist) and make sure the settings are as below.
Note in this example, the model physics is turned on (enabled). By setting LEPHYS=false
, the model would run an aqua-planet with all the physics switched off.
For more information on these switches see the relevant modules in the model code: yoephy.F90
(and yoewcou.F90 for the coupling to the wave model)
.
Expand | |||||
---|---|---|---|---|---|
| |||||
|
Initialisation
OpenIFS (and IFS) can be initialized either with real fields or idealized starting conditions.This is controlled both by the namelist switch N3DINI
and by the code in the model.
...
Code Block | ||
---|---|---|
| ||
&NAMCT0
N3DINI=0, ! normally 0 to initialise the model from a real atmosphere, but see ifs/module/yomdyncore.F90 for other possibilities. |
Orography, surface pressure and land-sea mask
In order to correctly run the aqua-planet in OpenIFS (and IFS), it is important that the orography field in the model is set to zero to ensure a flat surface. The surface pressure must also be adjusted to be consistent with the flat orography and the land-sea-mask in the model set to zero to indicate all sea-points.
There are two ways in which this can be achieved; either take an existing set of model initial files (the ICM*INI* files) and interpolate pressure to the surface, or run the model and adjust the orography and pressure whilst the model is running to prevent a sudden 'shock'.
Also see
ECMWF took part in the 2012 Dynamical Core Model Intercomparison Project (DCMIP). More information can be found here: https://www.earthsystemcog.org/projects/dcmip-2012/
Acknowledgements
OpenIFS would like to thank Sylvie Malardel (ECMWF) and Peter Bechtold (ECMWF) for their assistance in preparing this material
Related articles
Content by Label | ||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Excerpt Include | ||||||
---|---|---|---|---|---|---|
|