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Perpetual solar insolation in CAM5

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whannah
Perpetual solar insolation in CAM5

With CESM 1.2.2, I'd like to run an experiment with the solar zenith angle fixed to the equinox (~ March 20). I still want the diurnal cycle, just no seasons.
I've tried adding this to the CAM namelist:

solar_data_type  = 'FIXED'
solar_data_ymd   = 20000320

However, these changes have no effect, and I stil see the seasonal cycle in the model output. I've also tried using the "perpetual" namelist variable, and although I see this variable being referenced in various places throughout the source code, this also has no effect.

I found this old thread on this forum, but I didn't find those suggestions helpful in getting the solar input to stay fixed.
Any other ideas or suggestions?

thanks,
Walter

santos

I think that you cannot do this with CAM namelist settings alone, because other components also use the solar zenith angle.

I haven't tried anything like this, but isn't setting fixed orbital parameters in the driver namelist what you want? See the paleo documentation here:

https://www2.cesm.ucar.edu/working-groups/pwg/documentation/cesm1-paleo-...

Sean Patrick Santos

CESM Software Engineering Group

whannah

Thanks for the suggestion Sean, but I don't think this will work. I need to fix the solar data for a specific day of the year, instead of a specific year. I don't see a way to do that from the orbital parameters.

santos

I guess it depends on what you're doing specifically, but I would think that setting both the eccentricity and obliquity to 0 would make every day in the year the same as the equinox.

Sean Patrick Santos

CESM Software Engineering Group

whannah

Oh! That makes sense. I was thinking about it all wrong. That's a really great idea.... I'll try it out.

santos

Ah, I'm glad that you think it will work for you. =)

 

If there are any issues, please mention it, since I would assume that this feature is relevant to the paleoclimate working group.

Sean Patrick Santos

CESM Software Engineering Group

whannah

I just ran a half-year simulation with the orbital parameters set with zero eccentricity and zero tilt. I can confirm that the insolation is indeed fixed as it would be for a perpetual equinox. 

I would rather have the "perpetual" mode come back as a viable opion, but this works fine for now.

liufukaiouc@...

Hi Walter,


could you share your method? I set orb_obliqr and orb_eccen to zero in user_nl_cam, the insolation still has a seasonal cycle.


Thanks,

Kai

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