UKCA Chemistry and Aerosol Tutorial 12

Back to UKCA Chemistry and Aerosol Tutorials

What you will learn in this Tutorial

In this tutorial you will learn about how to quantify the radiative effects of aerosol simulated by GLOMAP-mode in UM-UKCA.

In the first task you will update your copy of the UKCA tutorial job to request radiative fluxes allowing the radiative flux perturbation (or effective radiative forcing) to be diagnosed based on difference in the fluxes between a pair of UM-UKCA jobs with some difference (e.g. pre-industrial and present-day emissions jobs).

The second task involves configuring a copy of the UKCA tutorial job to run in double-call configuration whereby the aerosol radiative effects can be diagnosed at each radiation timestep.

Task 11.1: Understand how the GLOMAP aerosol module tracks aerosol species and modes

TASK 10.1: Read section 12 (page 32) of the v8.4 UM Documentation Paper and refer to Tables 18, 19 and 20 on pages 33, 34 and 35.

Task 11.2: Run a copy of the standard UKCA job which tracks two OC components in the GLOMAP modes

Copy your copy of the standard UKCA tutorial job (xkvxe) from the UMUI and change the settings from the default UM-UKCA configuration for GLOMAP (setup 2) to instead use the 2-component OM configuration (setup 4).

To run the 2-component GLOMAP configuration, you will need to change the hand-edits in the UMUI to specify that you wish to run the model with additional aerosol tracers switched on.

First, open the hand-edits panel in the UMUI and find the line specifying to use the hand-edit

  ~mdalvi/umui_jobs/hand_edits/vn8.4/config_plume_scav_on_st.ed

If you open this file (read-only) in an editor you can get an idea of what the hand-edit does.

The hand-edit begins by introducing a new logical variable and parameter for the convective scavenging module in UKCA.

But the relevant section of the hand-edit for this task is where it edits the file SIZES setting the values of the array TC_UKCA which specifies which of the UKCA tracers are switched on (=1) or off (=0).

The order of the tracers here matches that specified in the code in the array nm_spec in the routine ukca_init.F90.

If you look in that file (e.g. checkout the package branch used in the model) you can check which tracers and switched on and off.

In the standard tracer configuration for UKCA specified in this config_plume_scav_on_st.ed hand-edit, tracers Ait_SOL_OC (index 106), Acc_SOL_OC (110), Cor_SOL_OC (116), Ait_INS_OC (121) and Nuc_SOL_OC (126) are set to 1 but tracers Nuc_SOL_SO (128), Ait_SOL_SO (129), Acc_SOL_SO (130) and Cor_SOL_SO (131) are set to zero.

To run with the 2-component OC configuration, you need to switch on these additional "SO" tracers to store the 2nd organic matter component in each mode, and also change the switch I_MODE_SETUP in the file CNTLATM from the value of 2 specified via the UKCA-MODE UMUI panel to instead be set to 4 for GLOMAP-mode setup 4.

An equivalent hand-edit for the 2-component OC configuration to apply these changes has already been produced which you can find in the file:

   ~gmann/stashfiles/config_plume_scav_on_st_MS4.ed

You can use a graphical difference tool like tkdiff or xxdiff to see the differences between the two files.

You see that running with the standard configuration of GLOMAP (I_MODE_SETUP=2) requires 83 tracers in the UKCA CheST configuration, with 20 coming from GLOMAP.

To run with the 2-component OM configuration of GLOMAP (I_MODE_SETUP=4) and the UKCA CheST chemistry required 3 addititional aerosol tracers, giving 86 in total.

If you compare against config_plume_scav_on_st.ed, you see that in config_plume_scav_on_st_MS4.ed TC_UKCA tracers 128, 129, 130 and 131 are set to 1 for the SO components in each of the soluble modes and the nucleation soluble OC mmr is no longer required as it has been replaced with SO mmr.

So to configure your copy of your initial UKCA tutorial job to run with 2-component OM, change the line in the UMUI hand-edits panel to point to

  ~gmann/stashfiles/config_plume_scav_on_st_MS4.ed

rather than

  ~mdalvi/umui_jobs/hand_edits/vn8.4/config_plume_scav_on_st.ed
  

Similarly, you also need to use an updated version of the RADAER hand-edit raderv2_vn84_ARCHER.ed to allow the 2-component OM configuration of GLOMAP to couple to the UM radiation scheme.

For this replace the hand-edit

  ~ukca/hand_edits/VN8.4/raderv2_vn84_ARCHER.ed

with the version for GLOMAP setup 4:

  ~gmann/stashfiles/raderv2_vn84_MS4_ARCHER.ed

The update to the hand-edit adds STASH requests to make available to RADAER the values of the partial volumes from the 2nd OM components at each radiation timestep to ensure they are included when calculating the GLOMAP aerosol optical properties.

To be able to add STASH requests for the additional OM components you also need to change the User-STASHmaster file in Atmosphere --> STASH --> User STASHmaster files, Diags, Progs and Ancils from

   ~ukca/userprestash/VN8.4/UKCA_Tr_StratTropAeroMODE.prestash

to instead use

   ~gmann/stashfiles/UKCA_Tr_StratTropAeroMODE_MS4.prestash

Once you have done this you should then add daily-mean STASH requests for section 34 items 128, 129, 130 and 131 for the SO component mmr's in each soluble mode as you already did for the OC mmr items in Task 10.

Finally, since you have asked the model to run with new tracers, you also need to specify how these should be initialised. Go to the Initialisation of User Prognostics panel off the STASH window. Scroll down until you see items 34128, 34129, 34130, 34131 and set the Option column to 3 so that these tracers are initialised to zero values for an NRUN.

Task 11.3 Examine the simulated total organic carbon in the original and two-cpt OC configurations

In the above Task 11.2 you ran a 2-component OC version of the UKCA tutorial job (xkvxe). You can also refer to gmann job xkwhh which I have configured in this way. See my xkwhg was the same as the UKCA tutorial job xkvxe except that I have added the extra STASH requests as in Task 10.

So by now you should have equivalent standard (as xkwhg) and 2-component OM (as xkwhh) versions of the UKCA tutorial job. In these jobs you have requested numerous daily-mean fields to be output in the .pa files.

So in your /work/n02/n02/ directory on ARCHER you should have .pa19991201 files for your standard and 2-component OM jobs.

Included in the extra STASH requests are the mass mixing ratios of OC (the standard organic component) and SO (the 2nd organic component) in each mode.

The OC mmrs are STASH section 34, items 126 (nucleation mode), 106 (Aitken-soluble), 110 (accumn-soluble), 116 (coarse-soluble) and 121 (Aitken-insoluble).

The SO mmrs are STASH section 34, items 128 (nucleation mode), 129 (Aitken-soluble), 130 (accumn-soluble), 131 (coarse-soluble).

These STASH item numbers and the details of the standard and 2-component GLOMAP configurations can be found in the UKCA UMDP section 12 Tables 19 and 20.

Note that there is no SO in the Aitken-insoluble mode as this contains only primary carbonaceous particles. Any SO or OC condensing onto the particles in the insoluble modes is immediately transferred over to the corresponding soluble mode following the "condensation-ageing" approach used by the model. This OC or SO condensing onto the insoluble particles is a kind of "coating" for the particles making the particles hygroscopic/soluble.

You could also try adding STASH requests for the mmr of the gas phase species MONOTER and SEC_ORG (STASH section 34, items 91 and 92).

As an example I have put here a link to a pdf OMcomparison showing global maps comparing surface OM fields between my jobs xkwhg (top-left) and xkwhh (top-right).

Page 1 of the pdf compares the "total POM mmr" at the surface which is the total particulate organic matter (POM) summing up the mass of OC and SO in each mode.

Pages 2 and 3 show comparisons of "total POM1 mmr" and "total POM2 mmr" which are the sum of the 1st and 2nd organic component over all the modes.

You can see from the example that the "total POM2 mmr" in xkwhg is zero everywhere. That's because in this job GLOMAP has the standard configuration with just one organic component.

By contrast the "total POM2 mmr" for xkwhh has considerable concentrations in vegetated continental regions. In this "I_MODE_SETUP=4" configuration, the "SEC_ORG" species (which contains the secondary organics from monoterpene oxidation) condenses into the "SO" component, whereas in xkwhg SEC_ORG condenses into the "OC" component.

The bottom left panel on each page shows a global map of the ratio of the field for the two model runs. One can use this kind of approach to track the fraction of the OM that is biogenic and anthropogenic.

Note however that we initialised the SO mmr's to zero at the start of the 1-day run. So the OC1 mmrs will be spinning down and the SO mmrs will be spinning up. The daily-mean values are averaging over values on each the 1-hour timesteps over which the UKCA chemistry and aerosol processes are integrated. So although the ratio shown in the bottom-left on page 2 is indicative of the biogenic fraction it should be treated with caution as the fields will not have spun-up/down yet.

This task illustrates how one can separate out the aerosol mass from different sources and track them separately via a different aerosol component.

One could also introduce a 2nd gas phase species like "SEC_ORG" to track different types of SOA. For example one could configure the model so that such a 2nd "SEC_ORG2" species held semi-volatile oxidised organic species with very low volatility oxidised organics held in the usual "SEC_ORG" species.

Written by Graham Mann 2014