### How to set up the radiation scheme for Palaeo-simulations?

I am trying to use
CCLM
for downscaling an
AGCM
simulation during

several time-slices in the last millennium (e.g.
LIA
,
MCA
). I need to adapt the Green

House Gas concentrations to that time. But the ico2_rad option do not

allow me to do so. How should I adapt the model for
GHG
concentrations in

such simulations.

There are two ways, a quick and a flexible one. For both first determine the equivalent CO2 concentration in ppm and convert it into mixing ratio by dividing by 658157.16

*
The quick one:
*

In src_radiation.f90 after the ico2_rad select case assign your mixing ratio to the variable zqco2

CASE (10) ! RCP85 scenario (for 1950 <= zyear <= 2150) ! eff. CO2 (all GreeHouseGases (GHG) considered) zqco2 = ( – 4.0501145412E+07_ireals & + 7.9386473439E+04_ireals * zyear & – 5.8292720579E+01_ireals * zyear*zyear & + 1.9002921793E-02_ireals * zyear**3 & – 2.3202412328E-06_ireals * zyear**4) * 1.519E-06_irealsEND SELECT zqco2 = …. ! insert your mixing ratio here

*
The flexible one:
*

in organize_physics.f90 change

IF (ico2_rad.GT.10 ) ico2_rad = ico2_rad_dto

IF (ico2_rad.GT.11 ) ico2_rad = ico2_rad_d

in src_radiation change

zyearmin = 1950to

IF (ico2_rad < 11) THEN zyearmin = 1950 ELSE zyearmin = ! .... put a year lower than the start year of your simulation period hereand change

CASE (10) ! RCP85 scenario (for 1950 <= zyear <= 2150) ! eff. CO2 (all GreeHouseGases (GHG) considered) zqco2 = ( – 4.0501145412E+07_ireals & + 7.9386473439E+04_ireals * zyear & – 5.8292720579E+01_ireals * zyear*zyear & + 1.9002921793E-02_ireals * zyear**3 & – 2.3202412328E-06_ireals * zyear**4) * 1.519E-06_irealsEND SELECT to

CASE (10) ! RCP85 scenario (for 1950 <= zyear <= 2150) ! eff. CO2 (all GreeHouseGases (GHG) considered) zqco2 = ( – 4.0501145412E+07_ireals & + 7.9386473439E+04_ireals * zyear & – 5.8292720579E+01_ireals * zyear*zyear & + 1.9002921793E-02_ireals * zyear**3 & – 2.3202412328E-06_ireals * zyear**4) * 1.519E-06_ireals CASE (11) !… last millenium zqco2 = !… insert your mixing ratio here ENDSELECTIn the CCLM namelist PHYCTL set

ico2_rad=11In the same way you can define several different mixing ratios with additional numbers 12, 13, 14 etc.

There are two ways, a quick and a flexible one. For both first determine the equivalent CO2 concentration in ppm and convert it into mixing ratio by dividing by 658157.16

The quick one:

In src_radiation.f90 after the ico2_rad select case assign your mixing ratio to the variable zqco2CASE (10) ! RCP85 scenario (for 1950 <= zyear <= 2150) ! eff. CO2 (all GreeHouseGases (GHG) considered) zqco2 = ( – 4.0501145412E+07_ireals & + 7.9386473439E+04_ireals * zyear & – 5.8292720579E+01_ireals * zyear*zyear & + 1.9002921793E-02_ireals * zyear**3 & – 2.3202412328E-06_ireals * zyear**4) * 1.519E-06_irealsEND SELECT zqco2 = …. ! insert your mixing ratio here

The flexible one:

in organize_physics.f90 changeIF (ico2_rad.GT.10 ) ico2_rad = ico2_rad_dtoIF (ico2_rad.GT.11 ) ico2_rad = ico2_rad_d

in src_radiation changezyearmin = 1950toIF (ico2_rad < 11) THEN zyearmin = 1950 ELSE zyearmin = ! .... put a year lower than the start year of your simulation period hereand changeCASE (10) ! RCP85 scenario (for 1950 <= zyear <= 2150) ! eff. CO2 (all GreeHouseGases (GHG) considered) zqco2 = ( – 4.0501145412E+07_ireals & + 7.9386473439E+04_ireals * zyear & – 5.8292720579E+01_ireals * zyear*zyear & + 1.9002921793E-02_ireals * zyear**3 & – 2.3202412328E-06_ireals * zyear**4) * 1.519E-06_ireals CASE (11) !… last millenium zqco2 = !… insert your mixing ratio here ENDSELECTIn the CCLM namelist PHYCTL setico2_rad=11In the same way you can define several different mixing ratios with additional numbers 12, 13, 14 etc.

There are two ways, a quick and a flexible one. For both first determine the equivalent CO2 concentration in ppm and convert it into mixing ratio by dividing by 658157.16

*
The quick one:
*

In src_radiation.f90 after the ico2_rad select case assign your mixing ratio to the variable zqco2

*
The flexible one:
*

in organize_physics.f90 change

IF (ico2_rad.GT.10 ) ico2_rad = ico2_rad_dto

IF (ico2_rad.GT.11 ) ico2_rad = ico2_rad_d

in src_radiation change

zyearmin = 1950to

IF (ico2_rad < 11) THEN zyearmin = 1950 ELSE zyearmin = ! .... put a year lower than the start year of your simulation period hereand change

CASE (10) ! RCP85 scenario (for 1950 <= zyear <= 2150) ! eff. CO2 (all GreeHouseGases (GHG) considered) zqco2 = ( – 4.0501145412E+07_ireals & + 7.9386473439E+04_ireals * zyear & – 5.8292720579E+01_ireals * zyear*zyear & + 1.9002921793E-02_ireals * zyear**3 & – 2.3202412328E-06_ireals * zyear**4) * 1.519E-06_ireals CASE (11) !… last millenium zqco2 = !… insert your mixing ratio here ENDSELECTIn the CCLM namelist PHYCTL set

ico2_rad=11In the same way you can define several different mixing ratios with additional numbers 12, 13, 14 etc.

I am also running some paleoclimate simulations with the cclm for different time slices starting 6000 years before present. I wanted to know, if I had to define several additional cases for different GHG s concentration for every period of study, what should be the year I have to give to zyearmin for every time slice? in my case the first year of the simulations is called 8240 and it refers to the year 4000 BC.

Thanks.

I am also running some paleoclimate simulations with the cclm for different time slices starting 6000 years before present. I wanted to know, if I had to define several additional cases for different GHG s concentration for every period of study, what should be the year I have to give to zyearmin for every time slice? in my case the first year of the simulations is called 8240 and it refers to the year 4000 BC.

Thanks.

I am also running some paleoclimate simulations with the cclm for different time slices starting 6000 years before present. I wanted to know, if I had to define several additional cases for different GHG s concentration for every period of study, what should be the year I have to give to zyearmin for every time slice? in my case the first year of the simulations is called 8240 and it refers to the year 4000 BC.

Thanks.

Your case does not differ much from the case above.
```
zyearmin
```

and
```
zyearmax
```

are only needed, if you fit your
GHG
concentration with a polygon. These values describe the validity range of the polygon. If you do not need this, you can comment out the following lines in src_radiation.f90:

! Define upper limits of fitted scenarios polynoms to avoid eloping zyearmin = 1950 IF (ico2_rad < 7) THEN ! SRES fitting zyearmax = 2100 ELSE ! RCP fitting valid until 2150 zyearmax = 2150 ENDIF! zyear can be modified, because it is only used for calculation of CO2 trends IF (zyear < zyearmin) THEN zyear = zyearmin ELSEIF (zyear > zyearmax) THEN zyear = zyearmax ENDIF

Your case does not differ much from the case above.

`zyearmin`

and`zyearmax`

are only needed, if you fit your GHG concentration with a polygon. These values describe the validity range of the polygon. If you do not need this, you can comment out the following lines in src_radiation.f90:! Define upper limits of fitted scenarios polynoms to avoid eloping zyearmin = 1950 IF (ico2_rad < 7) THEN ! SRES fitting zyearmax = 2100 ELSE ! RCP fitting valid until 2150 zyearmax = 2150 ENDIF! zyear can be modified, because it is only used for calculation of CO2 trends IF (zyear < zyearmin) THEN zyear = zyearmin ELSEIF (zyear > zyearmax) THEN zyear = zyearmax ENDIF

Your case does not differ much from the case above.
```
zyearmin
```

and
```
zyearmax
```

are only needed, if you fit your
GHG
concentration with a polygon. These values describe the validity range of the polygon. If you do not need this, you can comment out the following lines in src_radiation.f90:

! Define upper limits of fitted scenarios polynoms to avoid eloping zyearmin = 1950 IF (ico2_rad < 7) THEN ! SRES fitting zyearmax = 2100 ELSE ! RCP fitting valid until 2150 zyearmax = 2150 ENDIF! zyear can be modified, because it is only used for calculation of CO2 trends IF (zyear < zyearmin) THEN zyear = zyearmin ELSEIF (zyear > zyearmax) THEN zyear = zyearmax ENDIF

I am trying to use CCLM for downscaling an AGCM simulation during

several time-slices in the last millennium (e.g. LIA , MCA ). I need to adapt the Green

House Gas concentrations to that time. But the ico2_rad option do not

allow me to do so. How should I adapt the model for GHG concentrations in

such simulations.