Fail to have seasonal cycle in CESM2 CAM5 aquaplanet

[Hsing-Hung Chou]

Hi all,

I'm new to CESM and I'm using CESM2.1.3 to run an aquaplanet experiment.
What I want to do is running an CAM5 aquaplanet coupled with slab ocean (compset QSC5) and also with seasonal cycle but not with perpetual equinox orbital parameters setting.

I've changed the orbital obliquity from 0 to 23.5 in file user_nl_cpl which is
orb_eccen = 0.
orb_obliq = 0. -> orb_obliq = 23.5
orb_mvelp = 0.
orb_mode = "fixed_parameters"
, and then evoked ./preview_namelist, ./case.build, ./case.submit
The run was successfully built and ran for 1 year (which I assigned), but the variable SOLIN from the output files shows no seasonality.

I've noticed that there is a special note for aquaplanet saying that the orbital parameters setting in user_nl_cpl should not be modified.
(line 22 in user_nl_cpl: ! Do not modify any of the following orb_ entries)
Does this mean there's no way to turn on the seasonal cycle of solar insolation in CESM2 aquaplanet?
Or if there is any solution, what did I miss to modify?

Many thanks for your help.
Hsing-Hung

 

[brianpm]

Hi Hsing-Hung,

I believe that there is a code modification necessary to introduce seasons in the aquaplanet (in CESM2).

In the file cesm2_1_1/cime/src/drivers/mct/shr/seq_infodata_mod.F90 comment out the hard-coded aquaplanet lines, as shown here,

if ( infodata%aqua_planet ) then
infodata%aqua_planet_sst = 1
! infodata%perpetual = .true.
! infodata%perpetual_ymd = aqua_perpetual_ymd
endif

(Note that you can place the modified code into the case's SourceMods directory to avoid changing the code for all cases.)

Give that a try. Please report back if that produces the desired result (I think it should).

 

[Hsing-Hung Chou]

Hi Brian,
Thank you so much. It works perfectly!

Hsing-Hung

 

[thakur.abubakar]

Hello everyone,
I have a similar query. I want a perpetual July solar insolation in the aquaplanet (in CESM2). So far, I have just been able to introduce uniform zenith angle via cam namelist parameters, but that's not what I'm looking for.
Any help/guidance in this regard would be greatly appreciated.

Regards,
Abu Bakar

 

[thakur.abubakar]

Adding to my last post..

Just like Hsing-Hung, I tried setting orb_obliq=23.5 and then ran ./preview_namelists before ./case.build and ./case.submit, but this produces equinoctial insolation in SOLIN.

 

[Hsing-Hung Chou]

Hi Abu Bakar,

I'm not sure if this is what you want.
But to my experience, if I keep the variable infodata%perpetual and infodata%perpetual_ymd mentioned above by Brian unchanged (i.e. not block them out at about line 883, 884) and set the variable "aqua_perpetual_ymd" at about line 310 to the date I want then I can set the insolation just as the date I assign.
Also, the change of orb_obliq = 23.5 in user_nl_cpl is needed in this approach.

Not sure if this experience is helpful.
Hope this could solve your problem :)

Best regards,
Hsing-Hung

 

[thakur.abubakar]

Hi Hsing-Hung,

This has worked perfectly! Thank you so much :D

Best regards,
Abu Bakar