CMAQ5.2, grid size matching issue

Hi all,

I’m trying to run CMAQ5.2 for a fine resolution of 1.33 km. It crashes when it gets to the ADVSTEP, complaining about non-matching grid sizes, although all my inputs have the same dimensions. Here is the exact error message:

No inconsistent header data found on input files

 = = = = = = = = = = = = = =  End  FLCHECK = = = = = = = = = = = = = =

 Value for CTM_MAXSYNC:  300

 Value for CTM_MINSYNC:  60

 Value for CTM_ADV_CFL:  0.95

 Value for SIGMA_SYNC_TOP:  0.7

 Value for ADV_HDIV_LIM not defined; returning default :  0.9

 Maximum horiz. div. limit for adv step adjustment

 Top layer thru which sync step determined: 18

 *** ERROR ABORT in subroutine ADVSTEP on PE 000

 File grid sizes do not match CTM domain definition

Could you please help me with this problem.



This may be a problem with round-off error. What are the size of XCELL and YCELL specified in your GRIDDESC file? Are they 1330, or 1333.3333333D0?

This is a result of a serious standards-violation by the authors of ADVSTEP: REAL quantities ALWAYS have uncertainty due to both round-off issues (including in the compiler!) and quality-of-implementation issues. And these can be more subtle than many people realize…

The relevant Models-3 coding standard states that variables of REAL type should NEVER be tested for absolute equality.

That’s the reason for the carefully-tuned DBLERR() tests in the I/O API GRDCHK3 routine (which is what ADVSTEP should be using instead of its own hard-coded-and-unreliable test). Borrow the DBLERR code from ioapi/grdchk3.f and modify ADVSTEP to use that.

The XCELL and YCELL show up as 1333.333 in my GRIDDESC file,
Do you think they should be modified?

I repeat: the test needs to be fixed: I’ve seen machines where

> REAL*8, PARAMETER :: X = 1.0d0
> REAL*8 :: Y
> ...
> Y = 1.0d0
> IF ( X .EQ. Y )  ... !! turns out to be FALSE !!

Thanks @cjcoats - Had the same issue and this fixed it.

I Have a question about grid size. Is there any “independence of grid” issue in air quality modeling? Could you help me, please?
Thank you