Time Varying GHG

[HoWol76]

CO2, N2O, CH4: time varying, and included in the CMIP6 GHG forcing data set (so it might already be downloaded for the historical runs). Data is via http://climatecollege.unimelb.edu.au/cmip6 . I’m not sure which format is needed for ACCESS-ESM

Make UMUI job with static and time-varying data, see what changes.

[HoWol76]

Made two jobs with UMUIX, one with time varying concentrations, one with constant concentrations. Here's the differences:

in CNTLATM, the entries for CO2MMR and so on disappear from the namelist RUN_Radiation. New entries appear in the namelist CLMCHFCG:

• L_CLMCHFCG (Changed to True)
• CLIM_FCG_NYEARS(1) (156)
• CLIM_FCG_YEARS(1,1) (Years that data is given for, I assume 156 in total)
• CLIM_FCG_LEVLS(1,1) (An array with the starting value of 4.32598e-04)
• CLIM_FCG_RATES(1,1) (An array consisting only of values -32786.0 (Missing Value?)) The pattern of arrays then repeats, same array names, different last index. Probably different species.

Index	Initial Value	Final Value	Species
1	4.32598e-04	CO2
2	4.38078e-07	CH4
3	4.18499e-07	N2O
4	0.00000e+00	1.20505e-09	CFC11
5	0.00000e+00	2.25164e-09	CFC12
6	Does not appear
7	Does not appear
8	0.00000e+00	5.13044e-10	CFC113
9	0.00000e+00	4.84345e-10	HCFC22
10	0.00000e+00	1.50252e-11	HFC125
11	0.00000e+00	1.21031e-10	HFC134A

[HoWol76]

As data I found this download at the address provided above: http://www.geosci-model-dev.net/10/2057/2017/gmd-10-2057-2017-supplement.zip

There's an Excel file in there that has dedicated sheets for CO2, N2O, CH4, etc. These sheets contain, after some documentation, tables for the values in 4 columns (year, global, northern and southern hemisphere (I assume that's what NH and SH stand for))

[HoWol76]

It seems that the values supplied are in ppm/ppb/ppt, whereas I'm fairly certain UM needs them in MMR. So conversion is needed.

[HoWol76]

Wondering, what is the difference between CFC-11 and CFC-11eq (similarly CFC-12)

[HoWol76]

Check which values were used by the historical run

[HoWol76]

Claire suggests that the -eq concentrations are what would be needed to be added to CO2 in order to have the same effect (in case the model doesn't deal with this gas specifically).

[nickywright]

Link to paper: https://gmd.copernicus.org/articles/10/2057/2017/gmd-10-2057-2017.pdf, see Section 2.1.10 (paragraph before Section 2.2) and Table 5

[HoWol76]

1. Option 1: climate models implement a subset of 43 GHGs.
2. Option 2: climate models implement the four most important GHGs with their actual mole fractions explicitly, namely CO2, CH4, N2O and CFC-12, and summarize the effect of all other 39 gases in an equivalence concentration of CFC-11. For this purpose, we provide CFC-11 eq. concentrations (“full equivalence”).
3. Option 3: like option 2, but with a different split up of gases other than CO2, CH4 and N2O. Climate models implement the three most important GHGs with their actual mole fractions explicitly, namely CO2, CH4 and N2O, and summarize the radiative effect of the ODSs in a CFC-12 eq. concentration and the radiative effect of all other fluorinated gases as a HFC-134a eq. concentration. For this purpose, we provide CFC-12 eq. and HFC134a eq. concentrations (“full equivalence

[HoWol76]

Looking at one of the historic runs, these arrays contain values:

Field	Gas	2014 level in HI	Calc 2014 lvl
CLIM_FCG_LEVLS(1,1)	CO2	6.033164e-04	6.04047e-4
CLIM_FCG_LEVLS(1,2)	CH4	1.013009e-06	1.014417e-6
CLIM_FCG_LEVLS(1,3)	N2O	4.962693e-07	4.96871e-7
CLIM_FCG_LEVLS(1,4)	CFC11	1.104076e-09	1.10534e-9
CLIM_FCG_LEVLS(1,5)	CFC12	2.170460e-09	2.1731e-9
CLIM_FCG_LEVLS(1,8)	CFC113	4.698008e-10	4.7036e-10
CLIM_FCG_LEVLS(1,9)	HCFC22	6.844250e-10	6.8527e-10
CLIM_FCG_LEVLS(1, 10)	HFC125	6.354852e-11	6.3626e-11
CLIM_FCG_LEVLS(1, 11)	HFC134A	2.832775e-10	2.8362e-10

[HoWol76]

By the way, here are the molecular masses I've used (note: not all the gasses are actually in the UM, sometimes I looked on up without realising that it doesn't exists in the UM

molar_mass = {
    'air': 28.9647,
    'CO2': 44.01, 
    'CH4': 16.043,
    'N2O': 44.013,
    'HFC-134a': 102.03,
    'HFC-23': 70.01,
    'HFC-32': 52.024,
    'HFC-125': 120.02,
    'HFC-143a': 84.04,
    'CFC-11': 137.36,
    'CFC-12': 120.91,
    'CFC-113': 187.37,
    'HCFC-22': 86.47,
}

I convert from ppm to MMR by multiplying the ratio of the molecular weight of the gas and of air with the concentration.

[HoWol76]

The UM in src/atmosphere/short_wave_radiation/csenario_mod.F90 declares the parameter LENSCEN as the maximum length of scenarios.

This value is currently 800, and it is used to dimension the variables CLIM_FCG_YEARS, CLIM_FCG_LEVLS, and CLIM_FCG_RATES

[HoWol76]

Created a new build with this number increased to 1300: /scratch/w35/hxw599/access-esm/pmip-lm/build/bin/um_hg3.exe-20200903

[HoWol76]

Seems to work now.