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Carbon or Nitrogen patch negative

Xueli Huo


I am using ctsm5.1.dev012 and the model blows out with the error bellow:
2458: ERROR: Carbon or Nitrogen patch negative = -60.9515325869484 0.000000000000000E+000
2458: ERROR: limits = -60.0000000000000 -6.00000000000000
2458: ERROR: ERROR: carbon or nitrogen state critically negative ERROR in CNPrecisionControlMod.F90 at line 209

which I am sure the problem is the negative leafc_patch exceeds the cnegcrit = -6.e+1_r8 ! critical negative carbon state value for abort (gC/m2).

My questions are:

1) If I want to figure out why the negative value occurs at the patch, should I check the value of leafc at previous time step and the input (allocation and phenology) flux and output (litterfall) flux at the current time step ?

2) Could I just assign a lower value to cnegcrit or nnegcrit to jump over the error of the negative patch carbon or nitrogen ?
<cnegcrit phys="clm5_0" use_cn=".true.">-6.d+1</cnegcrit>
<nnegcrit phys="clm5_0" use_cn=".true.">-6.d+0</nnegcrit>
<cnegcrit phys="clm4_5" use_cn=".true.">-6.d+2</cnegcrit>
<nnegcrit phys="clm4_5" use_cn=".true.">-6.d+1</nnegcrit>
Could I use the same settings as that in clm4_5 ?


Keith Oleson
CSEG and Liaisons
Staff member
1. Yes. You might want to track leafc and the inputs/outputs from the beginning of the simulation if the simulation is not long to see how it is going negative.
2. Yes, you could try that. However, it might exceed the new cnegcrit later in the simulation.