Hi everyone,
The versions 1.2 of the ESM1.5 configurations add the ability to control orbital parameters at runtime through a UM namelist. In particular, the following variables can be set from the main atmosphere namelist:
ECCENTRICITY
: The eccentricity of Earth’s orbit.OBLIQUITY_RAD
: The obliquity of the Earth, in radians.DAY_PERIHELION
: The time of the perihelion passage, in days.LON_PERIHELION_RAD
: The longitude of the perihelion, in radians.
These notes detail how to set these parameters.
After cloning one of the available configurations:
locate the atmosphere/namelists
file contained in the control directory. A new optional namelist group &ASTRON_PERIODIC
containing the above variables can then be added. For example, to specify orbital parameters suitable for a 49ka experiment, we can add
&ASTRON_PERIODIC
ECCENTRICITY=0.01292,
OBLIQUITY_RAD=0.42647599,
DAY_PERIHELION=323.7698,
LON_PERIHELION_RAD =1.08997557,
/
It doesn’t matter where the &ASTRON_PERIODIC
group appears relative to the other namelist groups. However, note that aside from adding the new group, the order of the existing namelist groups should not be modified.
The &ASTRON_PERIODIC
group can also be left out from the namelist
file, in which case the model will default to the modern values used in previous releases:
&ASTRON_PERIODIC
ECCENTRICITY=1.6710222E-02,
OBLIQUITY_RAD=0.409092804,
DAY_PERIHELION=2.667,
LON_PERIHELION_RAD =1.7967674211761814
/
Feel free to ask any questions or let us know if you run into any problems with these changes!
Thanks @HIMADRI_SAINI for sharing the 49ka parameters used for testing during development.