Perpetual solar insolation in CAM5

[whannah]

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   = 20000320However, 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-toolkit/how/setting-orbital-parameters

 

[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-toolkit/how/setting-orbital-parameters

 

[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.

 

[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.

 

[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.

 

[whannah]

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

 

[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.

 

[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.

 

[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.

 

[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@gmail_com]

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

 

[liufukaiouc@gmail_com]

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