Opened 5 years ago

Closed 5 years ago

#1627 closed help (answered)

meteorologies in double call simulations

Reported by: ggxmy Owned by: um_support
Component: UM Model Keywords: double call simulations
Cc: Luke Platform: ARCHER
UM Version: 8.4


Dear CMS,

We run the UM RJ4.0 with some modifications. We use nudged double-call settings to evaluate the instantaneous radiative perturbations due to aerosols without any feedback or adjustment. So our simulations are set to be advanced with no aerosols. Therefore, the single call AODs are zero everywhere whereas the double call AODs are non-zero.

L_UKCA_AIE2=.FALSE. is set so that aerosols do not have an effect on the cloud.
L_UKCA_TROPHET=.FALSE. so aerosols are chemically decoupled as well.

So we expect identical meteorological fields between jobs with different aerosols. However they are slightly different from each other. For example, jobs tdyo.e and f are the same except that dust emission flux in the UKCA modal dust has been increased by a factor of 4 in the latter job than in the former. (Note that these jobs are created on ARCHER based on tdyo.d. tdyo.e and f on UMUI are dummies to reserve the slots.) If I look at the theta after timestep (STASH item 0-4) with xconv, for example, the plots look very similar to each other but the values of the scale are slightly different; the maximum values shown are 332.90 vs. 333.06 at the surface in July 2008. I think this is a small but not negligible difference. I wonder what causes such a difference in these jobs. If you have any idea please suggest me.

Masaru Yoshioka

Change History (5)

comment:1 Changed 5 years ago by luke

Hi Masaru,

You still have Ozone feedback on in these jobs, which will be causing differences. RADAER is on, as is 1st indirect effect, but I assume that you have dealt with all the aerosol effects correctly.

It is not possible to decouple the chemistry and aerosol completely, as the changes oxidant fields used in the aerosol chemistry will also affect the other chemical species. You will need to turn ozone feedback off.

Note that without any aerosol at all you will have a very clean atmosphere. You might want to turn CLASSIC back on. Please see my job xkolk which is a GA4.0+UKCA CheST job without any feedback (i.e. GLOMAP is off, CLASSIC is on) for chemistry studies where repeatable meteorology is required.


comment:2 Changed 5 years ago by luke

As an aside, if you are nudging you might want to turn ozone feedback off anyway, as it isn't needed.


comment:3 Changed 5 years ago by ggxmy

Thank you very much, Luke. That explanation is clear to me.

How do I turn off ozone feedback? Should I deselect "UKCA O3 in Radiation scheme" in the window "Section 34: UKCA Chemistry Coupling" in UMUI?


comment:4 Changed 5 years ago by luke

Hi Masaru,

Yes, that's correct. Sorry - I should have said that in my reply. This will then use the SPARC ozone dataset that is defined in the ozone climatology panel. For pre-industrial runs, this would need to be changed, as it will include an ozone hole.


comment:5 Changed 5 years ago by ros

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