Error reading the first BCON time step in centralized_io_module.F

CMAQ Run Time Errors and Issues
1
  • My BCON inputs were prepared using global model outputs whose data is 6-hourly; thus the BCON file has data at 0:00, 6:00, 12:00, and so on.
  • My daily CMAQ run starts at 8:00 (regional modeling for California is often done this way so that daily inputs/outputs cover mindnight to midnight in local time).
  • CMAQ (v5.3.3) stops with error saying it can’t read BCON data at the model start time.

It looks like the problem is in the subroutine centralized_io_init where it assumes BCON data at the model start date/time is available (which is not always true as in my case):

call retrieve_boundary_data (cio_model_sdate, cio_model_stime)

Fixing this is a bit tricky: I don’t think you can simply replace cio_model_stime in the above call with file_stime(f_bcon) because the subroutine may also read METBDY3D file which has its own start time (typically matching the model start time).
My quick-and-dirty solution was setting loc_jtime inside the subroutine retrieve_boundary_data to jtime if the optional argument vname is present (non-intialization call); to file_stime(f_bcon) if vname is not present (initialization call).
A more elegant solution should come.

2

To begin with, routine retrieve_boundary_data should never have been using READ3 to read boundary data; the original design called for using time-interpolation routine INTERP3, instead, and it is a significant degradation to the numerical-method order of accuracy to be using READ3 instead. And with 6-hour time steps, this degradation of accuracy is potentially quite bad.

As a hack, you could use M3Tools program m3interp to interpolate your BCON file to a finer time-resolution (hourly, at least), and use the resulting high-time-resolution file as your BCON: see https://www.cmascenter.org/ioapi/documentation/all_versions/html/M3CPLE.html for the program’s manual.

3

Hi bkoo,

We will provide an updated centralized_io_module.F as soon as possible.

Cheers,
David

4

Hi bkoo,

Please send me an email at wong.david-c@epa.gov so I can send you an updated code.

Cheers,
David