The result of GPP and NPP were close to 0 in July

[Li Ming]

Hi,
The version I am using is release-CLM5.0.35. I want to drive the model with my own 0.1° atmospheric forcing data combined with 0.1° domain that I created for my study area. Firstly, I created the 0.1° domain and surface files for the study area. Then I processed my atmospheric forcing data (named CMFD) into the same format as GSWP3. After inputting these files into the model, it ran without error for 10 years. However, the results showed that in most areas, GPP and NPP were close to 0 in July and other months, which is an abnormal situation. I am wondering what might be causing this issue. I will attach information about the atmosphere data, all null values have been filled.

I also have another question. I once ran the model for a period of time using my own 0.1° domain and surface files combined with GSWP3 data. However, there was a large difference between the grids in the resulting figure, and even some empty grids appeared. How can I avoid this situation?

 

[oleson]

I would start by examining the forcing data to see if it is reasonable. Look at the forcing variables in the history files, e.g., FSDS, FLDS, QBOT, TBOT, WIND, etc. You should also output those variables for a few days at a half-hourly or hourly time resolution to see if the diurnal cycle looks reasonable. The fact that your GSWP3V1 forced GPP looks fairly reasonable (aside from the empty grid) may point toward a problem with the forcing data or how it's being interpreted by datm.
I'm not sure what to say about your second question. The GSWP3V1 data is global (no missing values), so it might have something to do with your surface dataset maybe? Check your surface types in that empty grid.

 

[Li Ming]

Thank you for your reply. I checked the atmospheric data and found that the precipitation data was abnormal. After making the necessary modifications, the model ran normally. I have a question about spin-up. I want to use the CMFD atmospheric forcing data from 1979 to 2018 to create an IHIST case to study the GPP and NPP during this period. However, before doing this, I need to complete the spin-up process. I am confused whether I should use compset I1850Clm50Bgc or I2000Clm50Bgc for the spin-up process. I noticed that the only difference between these two is the CO2. Do you have any suggestions for me?

 

[oleson]

You can use the I2000Clm50BGC for the spinup process since you are only going to run the last segment of the historical.

 

[Li Ming]

Thank you. I will use the I2000Clm50BGC for the spinup process, But I always felt that the results were not quite correct during the simulation, my domain and surface files were 0.1°, and the atmospheric forcing data used was also 0.1° and three-hour resolution,other researchers using the same data set get very different results from mine. I tried to use other researchers' data and domain files to run on my own machine, but I got two results with large differences. In the second image, the results from other researchers are on the left,and the results run on my machine are on the right

 

[oleson]

I have seen similar patterns in high resolution simulations because the soil texture (percent sand/clay) datasets are at fairly coarse resolution by comparison. I would expect those patterns to smooth out with a long enough spinup.

 

[Li Ming]

Thanks for your help, I will try the 600 year spin up and hopefully solve this problem