4km CMAQ run nested in 12km

Hello all,

I want to run ICON and BCON for 4km grid to be run cctm for the timeframe of Feb 1,2023 through May 1,2023. I want to use 12km grid output that I will have for the regrid input. Do I need CONC or ACONC as input for ICON and BCON? For which timeframe I need to run 12Km domain for to be regridded in 4km domain? Thanks for your help.


CONC files are needed because they contain 3-D data (especially vertical layers, make sure you include all vertical layer data in your 12km CMAQ runs).

It depends on the temporal resolution of your 12km CMAQ CONC files. In general, hourly would be good.

NO, not 3 or 4 hours: you need a time step that resolves the features of the 12KM concentration field both temporally and spatially.

As a rule of thumb, you can regard a 10 M/S top-of-the-PBL wind field as a conversion factor between temporal and spatial resolution.

The WRF model is known to resolve 3DX* features in its met-fields, so that corresponds to a temporal resolution of
36,000 M / 10 M/S = 3600 S as the coarsest temporal resolution you should use (the Nyquist Theorem suggests you should use at most half of that; the direct translation of 12,000 M would be 1200 S = 20 minutes.