After updating our modeling platform from CMAQ v5.3.1
to v5.4
, we noticed that coarse mode sea salt concentrations were much lower with the new CMAQ version. So, we conducted some test runs, and the results are summarized in the slides linked here: Dropbox
This issue is similar to what’s reported in this thread: Low PM10 in CMAQv5.4
Unlike what’s reported there, however, we observed that turning on the AERO_M2USE
options didn’t make much impacts.
Here are our findings:
- Pleim et al. (https://doi.org/10.1029/2022MS003050) stated “[t]he most significant effect of the new model is to increase the mass dry deposition of the accumulation mode aerosols in CMAQ.” However, our test shows that differences between
v5.3.1
andv5.4
are much larger inASEACAT
than inANAJ
(slide 3). The slide also shows that switching on theAERO_M2USE
options made little difference on the modeled concentrations. - Slides 4-5 show process changes at the grid cell calculated by the IPR analysis. Both
v5.3.1
andv5.4
show similar net process changes forANAJ
. ForASEACAT
, however, a huge loss due to dry deposition (largely compensated by vertical diffusion) occurs during the first hour of the simulation withv5.4
, which results in initial concentration drop shown in the bottom plot of slide 3. This seems unrealistic. - We also looked at other coarse PM components:
ASOIL
andACORS
(slides 7-9).ASOIL
shows an initial concentration drop withv5.4
similar toASEACAT
. Its IPR result also shows a big dry deposition loss withv5.4
likeASEACAT
. However,ACORS
does not show such anomalies. This is strange; perhaps it has something to do with different size distributions among these coarse PM species?
My main concern is the huge difference in ASEACAT
between v5.3.1
and v5.4
(this has a big impact on our sea salt model performance with the new modeling platform). Is this expected with the new dry deposition model?
I’d appreciate any insight/suggestion on this issue and will provide more details about our tests if needed.
Thanks!