Changing the timestep in CAM-FV

[KumarR]

Dear CAM users,

Can I run CAM-FV with resolution of 1.9X2.5 by changing its model timestep from 1800s(default) to 600s?

Thank you.

 

[peverley]

Hi,

I believe you can change the model timestep by altering ATM_NCPL (which specifies how many timesteps and coupling periods occur over the NCPL_BASE_PERIOD). The defaults in CAM are ATM_NCPL=48 and NCPL_BASE_PERIOD="day" which means the timestep size is 1/48 days (30 min or 1800s).

If you instead want 600s timesteps, you can try changing ATM_NCPL in your case to 144 by running:

./xmlchange ATM_NCPL=144

Courtney

 

[KumarR]

Hi Courtney,

Thank you for your reply. So, is it technically correct to change the model timestep to 600s as it should also have an impact on radiation, microphysics etc, as I think CAM-FV uses same timestep (1800s) for different resolutions?

Thanks,
Kumar

 

[peverley]

Yes, I believe that CAM uses the same timestep (1800s) by default. Changing the timestep to 600s should indeed have an impact on your results. Here is a paper I found that is experimenting with exactly that: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2021MS002791

Does that answer your question?

 

[KumarR]

Thank you Courtney