CLM5.0 GPP

[yuecheng]

I am currently conducting a simulation study on GPP (Gross Primary Productivity) for July 2010 using CLM5.0. I have encountered a problem. I used the output hourly file variables "LAISUN", "LAISHA", "PSNSUN", and "PSNSHA" to calculate GPP as follows: GPP=(LAISUN * PSNSUN + PSNSHA * LAISHA） * 1.2e-5 * (12/44) * 3600. However, I cannot obtain the monthly GPP results that match the model output. What could be the reason for this?

 

[oleson]

I'm not sure, are you missing a conversion factor? You have 12/44 which presumably is gC/gCO2, but I think you need to multiply by 44 gCO2/1 mole CO2, and I'm not sure what 1.2e-5 represents.
I see this in the code:

gpp(p) = psnsun_to_cpool(p) + psnshade_to_cpool(p)

So I would check to see if GPP = PSNSUN_TO_CPOOL + PSNSHA_TO_CPOOL in the history output.