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B1850CN spinup issue

dear CLM forum,

we are doing an I1850CN spinup with CLM4.0 in order to produce the
initial condition for the CESM1.1.2 simulation that we will perform
at CMCC; with respect to the common implementation we are using a
finite volume grid at 1 degree (f09) with slightly different land-sea
mask in order to be consistent with the NEMO model that we adopt
for the ocean circulation
 
we are attaching the relevant summary plots for the total carbon
and nitrogen in the accelerated run (AD spinup) and the final
spinup (without acceleration)
 
we noted that even though the accelerated run seems to be close
to the equilibrium, the final spinup, that we performed after
about 850, 1000, 1250 and 2250 years of acceleration are not
in equilibrium and they show an almost constant trend during
the 50 years of simulations
 
is there an explanation for that? what can we do to check if we
are doing right, or to fix the problem?

thanks in advance,cheers,

Matteo Zampieri and Pier Giuseppe Fogli

 

slevis

Moderator
If after AD_SPINUP you run with EXIT_SPINUP before continuing to the FINAL SPINUP, then you're doing everything correctly as far as I can tell. This result suggests that the model is still spinning up in certain parts of the world. You may wish to determine which regions contribute to the trend. Maybe these regions were not in equilibrium in the AD_SPINUP phase, either.Sam Levis
 
hi Sam,

thanks for your answer!

yes we did the EXIT_SPINUP,

we are now attaching the plots with the spatial means and trends for
the last FINAL_SPINUP, which is now consisting of 100 years (no improvement),
and the same computed on the last 100 years of AD_SPINUP

interestingly, the areas displaying positive trends in the FINAL_SPINUP
sometimes correspond to areas of negative trend in the AD_SPINUP,is it normal?thanks,cheers,

Matteo
 

slevis

Moderator
It is normal in the sense that we ran 1850 in "final spin-up" mode for a few thousand years before considering the model spun up for the CMIP runs.Charlie Koven and his colleagues contributed an improved version of AD_SPINUP for clm4.5. I have not tested how long that one takes.Sam
 
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