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The aqua-planetOpenIFS includes a number of idealised configurations. In this article we explain how to configure the model for an 'aqua-planet' simulation. An aqua-planet is one that includes no topography and no land. It's a highly simplified representation of Earth but useful for a number of studies. | Info |
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| The aquaplanet configuration (enabled by namelist variable LAQUA) is based on the Neale & Hoskins publications: - Neale, R. B. and Hoskins B. J., 2000a, A standard test for AGCMs and their physical parameterizations. I: The proposal, Atmos. Sci. Letters, 1, pp. 101-107, DOI: 10.1006/asle.2000.0022
- Neale, R. B. and Hoskins, B. J., 2000b, A standard test for AGCMs and their physical parameterizations. II: Results for The Met. Office Model, Atmos. Sci. Letters, 1, pp. 108-114, DOI: 10.1006/asle.2000.0024
More recent general publications on the aqua-planet simulations: - Medeiros, B., et al,2008, Aquaplanets, climate sensitivity, and low clouds. Journal of Climate, DOIdoi: 10.1175/2008JCLI1995.1
- Blackburn, M., et al. (, 2013) , The Aqua-Planet Experiment (APE): CONTROL SST Simulation. Journal of the Meteorological Society of Japan, 91A. pp. 17-56. ISSN 2186-9057 doi: 10.2151/jmsj.2013-A02
Blackburn, M. and Hoskins, B. J. (, 2013) , Context and aims of the Aqua-Planet Experiment. Journal of the Meteorological Society of Japan, 91A. pp. 1-15. ISSN 2186-9057 doi: 10.2151/jmsj.2013-A01
See also for example, the PCMDI Aqua-Planet website. |
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Please note that the aqua-planet and other idealized configurations are a research tool and therefore may change between model versions. For further assistance with idealised configurations of OpenIFS, please contact: openifs-support@ecmwf.int. |
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Configuring OpenIFS for an aqua-planet simulation requires appropriate changes to:
- the model namelistsNamelists: to enable the idealized configuration and initial fields
- initial Initial files: to set orography & land-sea-mask.no changes to the code are required for the Neale & Hoskins cases; other configurations may require code changes
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:
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The SST modifications can be further changed using the variables defined in ifs/phys_ec/gp_sstaqua.F90:
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| title | Extra variables available in gp_sstaqua.F90 (not in namelist) |
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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. 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:
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&NAMDYNCORE
NOISEVOR=1, ! if 1 add initial noise in vorticity
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Mass conservation
Ensure that the Enable 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:
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| title | Ensure mass conservation : NAMDYN |
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&NAMDYN
LMASCOR=true, ! if true, apply mass correction.
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Edit namelist NAMCT0 in fort.4 to set the mass correction frequency:
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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:
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| title | Disable prognostic ozone scheme |
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&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).
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| title | To see NAEPHY namelist, click here to expand... |
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| title | Namelist settings for model physics: NAEPHY |
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| &NAEPHY
LEPHYS=true, ! switch the full ECMWF physics package on/off.
LEVDIF=true, ! turn on/off the vertical diffusion scheme.
LESURF=true, ! turn on/off the interface surface processes.
LECOND=true, ! turn on/off the large-scale condensation processes.
LECUMF=true, ! turn on/off the mass-flux cumulus convection.
LEPCLD=true, ! turn on/off the prognostic cloud scheme.
LEEVAP=true, ! turn on/off the evaporation of precipitation
LEVGEN=true, ! turn on/off Van Genuchten hydrology (with soil type field)
LESSRO=true, ! turn on/off orographic (VIC-type) runoff
LECURR=false, ! if true, ocean current boundary condition is used.
LEGWDG=true, ! turn on/off gravity wave drag.
LEGWWMS=true, ! turn on/off the Warner-McIntyre-Scinocca non-orographic gravity wave drag scheme.
LEOZOC=true, ! turn on/off the climatological ozone.
LEQNGT=true, ! turn on/off the negative humidity fixer.
LERADI=true, ! turn on/off the radiation scheme.
LERADS=true, ! turn on/off the interactive surface radiative properties.
LESICE=true, ! turn on/off the interactive sea-ice processes.
LEO3CH=false, ! turn on/off the ozone chemistry (for prognostic ozone).
LEDCLD=true, ! turn on/off the diagnostic cloud scheme.
LDUCTDIA=false, ! turn on/off computation and archiving of ducting diagnostics.
LWCOU=false, ! turn on/off coupled wave model (n.b. always off for OpenIFS model version 38r1).
LWCOU2W=false, ! turn on/off two-way interaction with the wave model (n.b. always off for OpenIFS model version 38r1).
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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.
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&NAMCT0
N3DINI=0, ! normally 0 to initialise the model from a real atmosphere, but see ifs/module/yomdyncore.F90 for other possibilities. |
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