question about quadratic ERROR

[syang]

Dear all,

I am currently running a reginal CLM case (I2000Clm50BgcCruGs). I used my own forcing dataset and domain maps. I am doing a 500-year spin-up. However, a quadratic error showed up after 100 years. In the cesm.log, it says "ERROR: Quadratic solution error" b^2 - 4ac is negative".

I looked up the guide and checked the similar questions in the forums. It probably resulted from the forcing dataset. However, I compared my dataset with GSWP dataset. All max, min, and mean values are similar and in the same level in the same region. Hence, I have no idea what caused this problem. If it is the problem of my forcing dataset, how can I track the errors and find the specific position of the error values in the forcing dataset? Any solutions will be appreciated! Thanks!

 

[oleson]

What version of CLM are you using? There was a similar issue here that was fixed at some point:

Quadratic solution error · Issue #756 · ESCOMP/CTSM

Brief summary of bug At year 1577 of a spinup with Princeton atm forcing data, I got a quadratic solution error (b^2 - 4ac is negative) that stopped the model General bug information CTSM version y...

github.com

 

[syang]

What version of CLM are you using? There was a similar issue here that was fixed at some point:

Quadratic solution error · Issue #756 · ESCOMP/CTSM

Brief summary of bug At year 1577 of a spinup with Princeton atm forcing data, I got a quadratic solution error (b^2 - 4ac is negative) that stopped the model General bug information CTSM version y...

github.com

I am using cesm2.2.0 and clm5. I tried many ways but still can not skip the quadratic error.

 

[oleson]

Did you try the code mods to PhotosynthesisMod.F90 that are shown here:

Merge branch 'SnowBurialFix' · ESCOMP/CTSM@622a196

Grass/crop snow burial fraction fix, and some other fixes (1) Crop/grass snow burial changed based on height and lodging (Danica Lombardozzi) - resolves ESCOMP/CTSM#516. Updates grass and crop...

github.com

 

[syang]

Did you try the code mods to PhotosynthesisMod.F90 that are shown here:

Merge branch 'SnowBurialFix' · ESCOMP/CTSM@622a196

Grass/crop snow burial fraction fix, and some other fixes (1) Crop/grass snow burial changed based on height and lodging (Danica Lombardozzi) - resolves ESCOMP/CTSM#516. Updates grass and crop...

github.com

Not yet. Does that mean I need replace all code showed in PhotosynthesisMod.F90 with updated code in the link? Like the figure below

 

[oleson]

Right. Remove the code with the "-" at the beginning of the lines and replace with the code that has "+"

 

[syang]

Right. Remove the code with the "-" at the beginning of the lines and replace with the code that has "+"

Thank you so much! I will try that.