Spin Up Convergene Check

[andrew.wilson]

Hi all,

I am working on accelerated spin up for CLM and was wondering if anyone has input on what they typically check for to determine convergence to a steady state. I have been looking at TOTVEGC, TOTECOSYSC, and NBP at a gridcell and "global" level, but also curious if anyone looks at specific BGC tracer values. I say "global" as I am only running a 3 gridcell configuration right now.

Ideally I'd like to be able to look at grid/column level quantities rather than global sums to determine if individual cells/columns have reached a steady state. Because of the current workflow I'm using I am able to save computational resource by essentially turning off acceleration at those sights independently once they reach a steady state. If anyone has papers they'd recommend I welcome those as well, I've read through a bit now, but everything I've found seems to be focused on global spin up and global carbon pools rather than gridcell or column level.

Andrew

 

[oleson]

There is an equilibrium spinup script called SpinupStability_BGC_v10.ncl located in tools/contrib in the latest tag of CLM/CTSM. One of the criteria for equillibrium is that 97% of the land gridcells must meet a total ecosystem carbon threshold of 1 gC/m2/yr. In other words, total ecosystem carbon must not be changing by more than 1gC/m2 per year. So each grid cell is evaluated per that threshold. The other equilibrium criteria are global as you've noted. Hope this helps.
If you are working on accelerated spinup methods, you might interested in this paper, a matrix method for accelerated spinup:

Liao, C., X. Lu, Y. Huang, F. Tao, D.M. Lawrence, C.D. Koven, K.W. Oleson, W.R. Wieder, E. Kluzek, X. Huang, Y. Luo, 2023: Matrix approach to accelerate spin-up of CLM5, JAMES, https://doi.org/10.1029/2023MS003625.