CMAQ-DDM produces NaN values at certain point

Hi All,

So, my CMAQ-DDM over East Asia worked fine until the point where some too big numbers popped out.

The SNO2/NOx from SENSGRID over three days:

Is it a numerical diffusion? I tried to reduce the time step but it didn’t help.

I remembered the same issue happened several years ago, and if my memory serves, it had something to do with the options incompatibility with the DDM.



It was caused by a rapid change in my emissions. No issue with the DDM.


Hey Amir,

I’ve been encountering a similar issue with my CMAQv5.2 DDM simulations, can you elaborate a bit more on what the issue was for your case?

Calvin Arter

Hi Calvin,

Check the emissions first. If my memory serves, when I merged bio emissions into anthro ones, I missed one hour so it resulted in a sharp change emission from one hour to another.