ICON and BCON data source

Hi everyone,
I am a new user of CMAQ and know little about it. I have a very simple question. I read the user guide but i am still confused of what is the data source of icon and bcon. I searched the CMAS website but there is no such descriptions about that. Could you please help me? Thanks so much!

Generally, the initial data of ICON/BCON is from clean atmosphere. In CMAQ, you can acquire it form ICON/BCON initial program by setting the ICON/BCON script. However, if you try to acquire the 2nd domain’s input data of ICON/BCON, you must get your 1st domain’s simulation results. Using those results and ICON/BCON’s nest program (choosing “m3conc” condition to make) to generate your nest domain’s input data of ICON/BCON.

BCON/ICON have two distinct modes of operation. When running BCON/ICON, the user must specify whether to generate BCs from: (1) an existing CONC file ( regrid ); or (2) an ASCII file of vertical profiles ( profile )

For further documentation, please see:


ICON User Guide Paragraph
BCON User Guide Paragraph

For a tutorial on how to use H-CMAQ model output available from the CMAS data warehouse to generate initial and boundary conditions, please see:



I see. Thanks so much!