About SSP Simulation GPP value is 0

[wzhang]

Dear All:
I am using the COMPSET=SSP370_DATM%GSWP3v1_CLM50%BGC-CROP_SICE_SOCN_MOSART_SGLC_SWAV ,and I want to simulate NPP, GPP for 2025-2100. The model finally runs successfully, but the result is unexpected, GPP shows 0 and NPP is negative, what is the reason for this, here are some files of my model settings.
Looking forward to your reply!

 

[slevis]

@wzhang
I see that maybe you are running this simulation over a single point. To troubleshoot, you will want to know what PFTs exist in the gridcell(s) where you see GPP = 0. It's possible that crops will give GPP = 0 in the first year of a simulation. It's also possible that other PFTs will not grow if the climate is unfavorable.

Ultimately you will have to think about possible reasons that can lead to GPP = 0 and investigate on your own until you find the root cause. You may also gain insight from running a simulation with default datasets rather than custom datasets, so as to see how the model behaves when GPP > 0.

 

[wzhang]

@wzhang
I see that maybe you are running this simulation over a single point. To troubleshoot, you will want to know what PFTs exist in the gridcell(s) where you see GPP = 0. It's possible that crops will give GPP = 0 in the first year of a simulation. It's also possible that other PFTs will not grow if the climate is unfavorable.

Ultimately you will have to think about possible reasons that can lead to GPP = 0 and investigate on your own until you find the root cause. You may also gain insight from running a simulation with default datasets rather than custom datasets, so as to see how the model behaves when GPP > 0.

Dear slevis.

I used the default anomaly forcing to run the results are correct, but I have some confusion about the default anomaly forcing, for example, the default anomaly forcing data is the monthly scale data, the unit of precipitation is mm/s, but its value is really 1.08mm/s, this is not unreasonable, I downloaded the monthly scale precipitation data of CMIP6 from ESGF official. I downloaded the monthly scale precipitation data of CMIP6 from ESGF official, its unit is also mm/s, and its value is about 1.08×1e-5 kg m-2 s-1, 1.08×1e-6 kg m-2 s-1. The same goes for the temperature data, its unit is K, but its value is really 1~6 K, which is even more unreasonable if it is converted to ℃. Can you tell me why this is so?

Looking forward to your reply！

 

[oleson]

I believe the units attribute on the anomaly forcing precipitation file is incorrect. It is not mm/s, but instead is unitless. It is supposed to be a monthly multiplicative factor on the input precipitation.