Post-AD spinup: extreme carbon values at Arctic gridcells after exiting AD mode (CESM 2.1.3)

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Claude_9910

Runze HU
New Member
Hello,

I am running CLM5 BGC spinup (CESM 2.1.3) with the following compset:1850_DATM%GSWP3v1_CLM50%BGC_SICE_SOCN_MOSART_SGLC_SWAV Resolution: f19_g17, soil_layerstruct = '20SL_8.5m'

AD spinup settings:

  • CLM_ACCELERATED_SPINUP=on, 300 years
  • At end of AD: TOTECOSYSC = 231 PgC (global), max gridcell = 8,022 gC/m² ✓
Post-AD spinup settings (startup + finidat):

  • RUN_TYPE=startup, CLM_ACCELERATED_SPINUP=off, CLM_FORCE_COLDSTART=off
  • finidat = AD restart file (spinup_state=2)
  • Result: TOTECOSYSC jumps to 2887 PgC, max gridcell = 1,089,668 gC/m² at lat 82.4°N

  • The extreme values (>100,000 gC/m²) appear only in Arctic/permafrost gridcells and are physically impossible. There are 241 such gridpoints. The lnd.log shows Spinup factors = 1.0 1.0, suggesting no de-acceleration was applied, yet the values are ~12.5x higher than the AD equilibrium.

    I also tried branch mode (CONTINUE_RUN=FALSE) but got the error: Error in entering/exiting spinup - should occur only when nstep = 1

  • AD case XML settings:
    COMPSET: 1850_DATM%GSWP3v1_CLM50%BGC_SICE_SOCN_MOSART_SGLC_SWAV
    RES: f19_g17
    CLM_ACCELERATED_SPINUP: on
    CLM_FORCE_COLDSTART: on
    RUN_TYPE: startup
    STOP_N: 10, STOP_OPTION: nyears, RESUBMIT: 29 (300 years total)
    REST_N: 5, REST_OPTION: nyears
    user_nl_clm (AD):

    hist_nhtfrq = 0
    hist_mfilt = 12


  • Post-AD case XML settings (what I tried):
    CLM_ACCELERATED_SPINUP: off
    CLM_FORCE_COLDSTART: off
    RUN_TYPE: startup
    CONTINUE_RUN: FALSE
    RUN_STARTDATE: 2150-01-01
    STOP_N: 10, STOP_OPTION: nyears, RESUBMIT: 89
    user_nl_clm (post-AD):
    hist_nhtfrq = 0
    hist_mfilt = 12
    finidat = 'AD_1850.clm2.r.2150-01-01-00000.nc'

    AD restart file:
    spinup_state = 2
    soil1c_vr: all zeros
    litr1c_vr: all zeros
    T_SOISNO: normal values (~232K in deep layers)

    Questions:
    1. Why do Arctic gridcells get extreme carbon values when exiting AD mode?
    2. What is the correct procedure to transition from AD to post-AD spinup for a global simulation with permafrost?
  • Thank you.
 
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Claude_9910

Runze HU
New Member
$ grep -i "INITIAL_CSTOCKS\|spinup_state\|Spinup factors\|exit_spinup\|Multiplying"
~/run/lnd.log.0:704440.sqd.260605-025056 | head -20

INITIAL_CSTOCKS = 3*200.000000000000 ,

INITIAL_CSTOCKS_DEPTH = 1.50000000000000

spinup_state, (0 = normal mode; 1 = AD spinup; 2 AAD) : 0

Spinup_state 0

Spinup factors 1.00000000000000 1.00000000000000

exit_spinup F restart_file_spinup_state 2

Multiplying stemc and crootc by 10 for exit spinup

Multiplying stemn and crootn by 10 for exit spinup
 
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slevis

slevis

Moderator
Staff member
If you are following the User's Guide
then you are spinning up the way that you should.

I have not looked at spin-up behaviors in specific regions, so I will let others chime in. Though one potentially tangential thought to consider is that, when I see huge numbers in my results, I sometimes find that missing values (e.g. 1e36) got mixed with my results. So looking at your max grid cell, you may gain insight from outputting variables of interest at the column and/or landscape and/or patch level.
 
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Claude_9910

Runze HU
New Member
slevis said:
I just happened to notice the mention of latitude in a relevant section of the Technote;
Click to expand...
Thank you, this clears it up. I checked my output and the elevated SOM spans all latitudes (not just the high-latitude band), which matches the pools being multiplied back by a_i on exit from AD mode, plus the geographic term you pointed me to. So it's the expected accelerated-spinup behavior, not a bug. Much appreciated!
 
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