question about double CO2 exp.

[tao_zhang@noaa_gov]

Dear All,

I am using CAM3 climatological SSTs as model forcing to do a double CO2 perturbed run,
and I want to output the history file in the frequency of timestep. Specifically,
I'd like to take a look at the results in first 2 timesteps because the feedbacks are
not involved at that time.

For this purpose, I have read the user guide, but I am still not clear how to make
the change correctly.

1) In Page 66 of Table B.1: CAMEXP namelist variables(see user guide),
I find that the default value for variable "CO2VMR" is 3.550e-4. But I have
checked each files in /cam1/models/atm/cam/bld, and can not find the name of
"CO2VMR". So How to make a double CO2 (2X 3.550e-4) in the model?
Also, I want to know why NCAR gives the value of 3.550e-4 for CO2 in the model
run using climatological SSTs as forcing? Where is it from?

If another CO2 file in the path "inputdata/atm/cam2/ggas/noaamisc.r8.nc" is used
for the run with monthly observed SSTs?

2) How to set the output frequency of timestep correctly?

Your suggestions are highly appreciated.

tao

 

[mvr]

hi...

as noted in the user's guide, the co2 volume mixing ratio
(CO2VMR) is 3.55e-4 by default...to run at twice that level, simply
specify the namelist variable CO2VMR to be 7.1e-4...if you want
to ramp the co2 levels up to a cap of 2x, check out the namelist
variables: SCENARIO_GHG, RAMP_CO2_START_YMD,
RAMP_CO2_CAP, and RAMP_CO2_ANNUAL_RATE for how to
do that...

the default value for CO2VMR is a 1990 level (355 ppmv)...

to set the output frequency of the primary history tape to
once-per-timestep, set the namelist variable NHTFRQ(1)=1,
as described in the user's guide...

i hope that helps,
-mathew

 

[tao_zhang@noaa_gov]

Hi, mvr,

Thanks very much for your valuable suggestion.

1)
Listed below is key part of my runscript with modified setting for my purpose.
I am not sure if this is the exact suggestion you have made for my concern.
(please look at the last 2 sentences)
...................
## Create the namelist
cd $blddir || echo "cd $blddir failed" && exit 1
echo "Building the namelist."
$cfgdir/build-namelist -s
-case $case
-runtype initial
-o $rundir/namelist
-namelist "&camexp nelapse=$nelapse,mss_irt=0,CO2VMR=7.1e-4,NHTFRQ(1)=1 /"
|| echo "build-namelist failed" && exit 1
...........................

2) You mean that the default value for CO2VMR is a 1990 level (355 ppmv).
Does this value come from IPCC or other sources?

What's the function of CO2 data under the directory "inputdata/atm/cam2/ggas/"?
I am not sure if it is used for the run with monthly observed SSTs?

3) If I want to save the primary history tape with 3 frequncey (timestep, daily,
monthly) at the same run, How should I set for "NHTFRQ" ?

Hope to hear from you,
Thanks again for your comments.

tao

 

[mvr]

1) looks good
2) i know nothing more of the origin of the default value for co2vmr
other than it is supposed to represent a 1990 level
3) from 3.1 of the user's guide:
"If the user wishes to see a field written at additional time
frequencies (e.g. daily, hourly), additional history files must be
declared."

and from table b13 of the user's guide for entry NHTFRQ:
"Array of write frequencies for each history files series. If
NHTFRQ(1)=0, the file will be a monthly average. Only the first file
series may be a monthly average. If NHTFRQ(i) >0, frequency is
input as number of timesteps. If NHTFRQ(i)

 

[tao_zhang@noaa_gov]

Thanks for your nice reply.
As for the third question, I still want to make it clear.

Assuming that I only want to output the defaut fields listed in Table 3.1
with 3 frequncey (timestep, daily,monthly) at the same run, If I only need to
set nhtfrq(1)=0 nhtfrq(2)=1 nhtfrq(3)=-24 in the namelist?

Assuming that I want to add 3 additional fields that not on by defaut (still with
3 frequency), If I have to add the setting FINCL1=var1,FINCL2=var2,FINCL3=var3
in the namelist? But there are only six FINCL (FINCL1,...FINCL6), if it is possible
to add more than 6 fields that not on by defaut?

thanks very much,
tao

~

 

[mvr]

Those fields of table 3.1 marked as default will automatically be
included on the FIRST history tape, not the secondary history
tapes...any fields you want on the secondary tapes must be added
using the fincl namelist vars...

Each of the fincl variables (fincl1,fincl2,fincl3,fincl4,fincl5,fincl6)
is an array for the output fields you want to add to each respective
tape (1-6)...

So, your monthly tape (nhtfrq(1)=0, as mentioned earlier) will have
all the default fields and any fields added using fincl1...

fincl1='var1','var2',etc

your timestep tape (nhtfrq(2)=1) will have ONLY the fields you add
using fincl2...

fincl2='var3','var4',etc

and likewise, your daily tape (nhtfrq(3)=-24) will have only the fields
you add using fincl3...

fincl3='var5','var6',etc

-mathew

 

[tao_zhang@noaa_gov]

I got it. Thanks very much for your wonderful reply.
tao