Questions about parameter tuning and spin-up

[Jeline]

Dear all,
I’ve run into difficulties regarding parameter calibration and spin-up procedures.

(1) Parameter calibration:
Our goal is to calibrate PFT-related parameters in CLM using an I compset to improve the accuracy of simulations, and then run the model with a B compset.

• Does CESM provide any official tools for parameter calibration?
• If not, is it feasible to perform calibration using other approaches?
• Are there any recommended or widely used methods?

I’m concerned because running CESM is computationally expensive, making it impractical to perform repeated runs with algorithms like genetic optimization. Also, I found very few discussions about parameter calibration on the forum, which makes me a bit uncertain about the best approach.

(2) Spin-up question:
I plan to run a BHIST_BPRP simulation (1980–2020) to study the climatic effects of global afforestation. As I understand it, there seem to be three possible spin-up options:

1. Run B1850 with the default forcing data for 1850–1980.
2. Repeatedly cycle the 1980–1990 forcing data to spin up B1850 for 1900–1980 (80-year spin-up).
3. Run B1850 with the default forcing data for 1900–1980 (80-year spin-up).

Which of these three approaches would be considered correct or most appropriate?
Sorry if some of my questions seem basic. I would be truly grateful for your advice and any guidance you could share.
Many thanks in advance!