Dust scheme Leung 2023

[adagj]

Relevant issue from cesm: NCAR/cesm_dev#19

Discussion on dust from cesm_dev: NCAR/cesm_dev#30

@rosiealice @oyvindseland @mvdebolskiy @gold2718

[adagj]

These are my notes from the CESM meeting the 5th of November:

Impact of Leung 2023 - new dust scheme:

TOA Radiation impacts
Increase in LWCF (+1.14 W/m2)
Slightly stronger SWCF (-0.47 W/m2)
Decrease in clear sky SW (-0.77 W/m2)
Slight reduction in clear sky OLR (+0.29 W/m2)
RESTOM increases 0.42 W/m2 → 0.68 W/m2

AMIP mode. Increase in LWCF: from 22.2 to 23.3 W/m2, increase in the NH stormtrack region. More aerosols, ice nucleation, more high clouds, more low cloud activation. RESTOM increases from 0.48 to 0.68 W/m2. To high SWCF, the new dust scheme didn’t have a huge impact, but caused slightly stronger SWCF. Will try to increase sea salt emissions, trying to get the SWCF down.

[oyvindseland]

I have tested Leung 2023 in a NorESM 2.5 version version with standard CLM. (nf2000_ne30pg3_ne30pg3_mtn14_20250120)
It does not look like there is any problems in translating Leung to Oslo-Aero.

It turned that there was an error in the emissions / land surface inherited from the CESM version so stopped doing these tests.

The results from the cesm issue above look much more sensible, although still quite high over Australia.

However to use Leung clm one must use z0param_method = 'Meier2022' instead of z0param_method='ZengWang2007'
z0param_method = 'Meier2022' does not work with FATES
So for the time being the alternative dust formulation can only be tested using CLM without FATES.

[rosiealice]

So is the consensus that we would like ideally to use the Leung dust scheme?

I am not sure which element of the Meier parameter scheme it needs, or whether it was just calibrated with that as the boundary layer configuration.

[oyvindseland]

I do not actually have strong preferences myself. The test I did was not promising for the new formulation.

For now I think the old parameterisation is better, see e.g.
https://aeroval-test.met.no/andrear/pages/intercomp/?project=NorESM2.5&experiment=LatestNorESM2.5-vs-obs&station=NAFRICA&observation=AeronetSun&parameter=od550aer#

Based on the results in issue above it looks that some of the more recent CAM updates has corrected the errors found in my test. E.g the dust column burden over Australia increased by a factor of 100 and is not supported by AOD measurments either.

The new parameterisation looks better over Africa, although this can likely be improved by just scaling the emissions. Note that NorESM2-MM has higher AOD over North Africa with Zender parameterisation.

#72

[rosiealice]

I think it is possible that the dust behaviour may change as a function of using FATES NOCOMP (and the different LAIs and fluxes that will entail) and so which model performs better might be swamped by that. So I am slightly minded to push the discussion of that further into the future when that is more stable. In the interim, we could think of maybe doing some experiments with parameters that we think might have big impacts to think about how we might tune that if we see large issues?

[oyvindseland]

I agree with the conclusion that we can push it more into the future. I notice that that CESM use global dust emissions as one of their main tuning parameters so we may want to test that independent of the choice of parameterisation.