Dust emission in CMAQv5.4

CMAQ
1

Hi all,
I am curious about the dust module in CMAQv5.4. Upon checking the run.cctm.csh script for CMAQv5.4, it seems that CMAQv5.4 only provides inline windblown dust option with the P-X land scheme required in WRF. Am I right? Do we have other options for performing dust simulations? For example, if I use NOAH-LSM in WRF and would like to proceed with dust simulation using CMAQv5.4, what’s the next step?
Any comments are highly appreciated!
@Ben_Murphy @lizadams
Best,
Ryan

2

We disabled this option because we have not tested the NOAH LSM with CMAQ 5.4’s wind blown dust (WBD) module. CMAQ’s WBD module expects soil moisture at PX’s top layer depth of 1 cm. NOAH’s top layer is 10 cm thick. This inconsistency can lead to near-zero dust emissions in the west. Here is an example of top layer volumetric soil moisture for PX (left) and NOAH (right):

soil_moisture_px_vs_noah
soil_moisture_px_vs_noah1920×1131 253 KB

You see that NOAH has a lot more moisture out west and the values are more uniform throughout the domain. Differences in soil texture characterization also merit further sensitivity testing. We intend to reconcile these issues and reduce CMAQ’s PX constraints in the future. If you are interested in developing the WBD module with NOAH you can comment out:

                 XMSG = 'WB_DUST requires PX LSM (PX_VERSION Y)'
                 Call M3EXIT( PNAME, 0, 0, XMSG, XSTAT1 )

in centralized_io_module.F. That change will allow the model to run. You might then want to try adjusting the gravimetric soil moisture calculation:

          soimt( c,r ) = Met_Data%soim1( c,r )
  &                      * 1000.0 / ( 2650.0 * ( 0.511 + 0.126 * sandf  ) )

in DUST_EMIS.F to account for the higher soil moisture NOAH. I tried simply dividing volumetric soil moisture by 10 but that resulted in far too much dust. Something like .8 results in emissions that are closer to a PX configuration, but that’s arbitrary and difficult to justify.

4 Likes
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Hi Jeff,
I appreciate your insights and will try it.
Thanks!

Best,
Kai

4

Hi Kai,

if you’re planning on adjusting NOAH soil moisture for compatibility with the CMAQ WBD module, you might also be interested in this earlier discussion in post 13 of this thread

and specifically the reference to the Campbell et al. study.

Christian

2 Likes
5

Hi Christian,
Thanks for bringing this up. I did aware of the study by Campbell et al. and will look through the discussion carefully.

All the best,
Kai