How do I use interannual variable LAI in CLM5

[xiaom]

Hi, the version of the model I'm using is CESM2.1.3, and the compset is FHIST (HIST_CAM60_CLM50%SP_CICE%PRES_DOCN%DOM_MOSART_SGLC_SWAV). I plan to use annually varying LAI in the model. I can provide a 10-year monthly LAI dataset based on other satellite observations, but I found that the variable related to LAI in the surfdata file ('monthly_lai') has a time dimension of time=12, without an option for interannual variation. I'm not sure how to implement the use of interannually varying LAI. Could you give me some suggestions? Or is it that the compset I chose is not suitable?
Looking forward to your reply, thank you.

 

[slevis]

Interesting question. You are using the correct compset. I'm not aware of infrastructure in the code to handle this. In case I'm wrong, I'm pinging @wwieder @oleson @erik.

But if I'm correct, then you would need to make modifications to the datasets and the code.

 

[slevis]

An inconvenient alternative that does not require modifying code:
You could run one year at a time. Each year you could change the fsurdat file to the one with the new LAI and branch the simulation.

 

[oleson]

There is an LAI streams capability in CLM5. The default setting is for years 2001-2013. This post may be useful:

Some question about spin up

Dear, Hello, everyone. I just started learning CLM models and I have a few questions about spin up. 1. How many years of atmospheric forcing data is good to spin up? Does the use of atmospheric forcing data for different time periods affect the effect of spin up. For example, if I want...

bb.cgd.ucar.edu

 

[xiaom]

There is an LAI streams capability in CLM5. The default setting is for years 2001-2013. This post may be useful:

Some question about spin up

Dear, Hello, everyone. I just started learning CLM models and I have a few questions about spin up. 1. How many years of atmospheric forcing data is good to spin up? Does the use of atmospheric forcing data for different time periods affect the effect of spin up. For example, if I want...

bb.cgd.ucar.edu

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Thank you very much for your reply. I have a general understanding of what I need to do now, but I have a few specific questions:

1. I am using the compset FHIST. Do I need to perform a spin-up? How many years would you recommend for the spin-up period?
2. If I set use_lai_streams = .true., should I set do_transient_crops and do_transient_pfts to .false.?
3. The default time range in the LAI streams file is 2001-2013. If I want to use LAI data beyond this time range, do I just need to change the time dimension in this file? Or do I also need to modify some code in SatellitePhenologyMod.F90 to ensure the model reads it correctly?
4. The publicly available LAI data is TLAI, which does not have a PFT dimension. I am considering using the PCT_CFT, PCT_CROP, PCT_NAT_PFT, and PCT_NATVEG values from the surfdata to obtain the proportion of each PFT and calculate the LAI value for each PFT in the LAI streams. Is this approach feasible?

 

[xiaom]

An inconvenient alternative that does not require modifying code:
You could run one year at a time. Each year you could change the fsurdat file to the one with the new LAI and branch the simulation.

Thank you for your kind reply. I had attempted to use this method, but due to the long queue time for task submission on the server, I decided to discontinue this approach. Therefore, I would like to explore other methods.

 

[slevis]

I responded to some of your quesitons here:

Questions about using lai_streams in CLM5

I want to use a LAI with interannual variability (1980-2020) in the model. From previous posts, I roughly understand that lai_streams can be used to achieve this, but I still have some doubts that I hope you can help me clarify. The compset I am using is FHIST...

bb.cgd.ucar.edu

The question about spin-up is a personal choice that you have to make on your own. It will likely help to look at model output and model trends to decide.