Greetings!
I am trying to set up some simulations I can use to compare the equilibrium behavior of different forcing scenarios. What I would like to wind up with is something that allows me to do the following:
* start with a baseline case (standard GHG levels, land cover, etc) and run until the simulation reaches equilibrium (eg, when the mean global temperature averaged over the last N years stops changing)
* make some change to the forcings (eg, 2xCO2, change surface albedo in some areas, etc.) and run the changed scenario to equilibrium
* compare the test case w/ the baseline
I would like for the baseline case to be something similar to modern day, so I tried starting with F2010climo. Unfortunately, I'm having trouble setting a fixed CO2 level for the experimental case. I've seen references in the forums to adding the following to user_nl_cam:
scenario_ghg = 'FIXED'
co2vmr = NNN
but when I try that I get this error:
CAM build-namelist - ERROR: When flbc_file is used cannot set scenario_ghg = 'FIXED'
From some comments in the CESM ChangeLog file it sounds like tweaking co2vmr might not be a common practice in more recent versions of CAM. (There is a remark about it not being widely used from late 2016) I see that F2010climo uses a boundary layer file:
flbc_file = '$DIN_LOC_ROOT/atm/waccm/lb/LBC_2010climo_CMIP6_0p5degLat_c180227.nc'
which appears to be a year worth of monthly average concentrations. To get a new fixed CO2 concentration, would it be reasonable for me to create a second version of the flbc_file with M times the values from the original? Or would that give weird results for some reason? Alternatively, is there a way to get scenario_ghg = 'FIXED' to work with CAM6?
On a related note, i'm curious how the values from flbc_file are used in an F2010climo compset. Are these just replayed every year as-is for the length of the simulation? Or is there some time dependence (eg, maybe they are scaled up by some factor each year as the simulation progresses?) I'm hoping for the former, since otherwise my equilibrium simulation won't equilibrate. :)
Thanks!
-Rob
I am trying to set up some simulations I can use to compare the equilibrium behavior of different forcing scenarios. What I would like to wind up with is something that allows me to do the following:
* start with a baseline case (standard GHG levels, land cover, etc) and run until the simulation reaches equilibrium (eg, when the mean global temperature averaged over the last N years stops changing)
* make some change to the forcings (eg, 2xCO2, change surface albedo in some areas, etc.) and run the changed scenario to equilibrium
* compare the test case w/ the baseline
I would like for the baseline case to be something similar to modern day, so I tried starting with F2010climo. Unfortunately, I'm having trouble setting a fixed CO2 level for the experimental case. I've seen references in the forums to adding the following to user_nl_cam:
scenario_ghg = 'FIXED'
co2vmr = NNN
but when I try that I get this error:
CAM build-namelist - ERROR: When flbc_file is used cannot set scenario_ghg = 'FIXED'
From some comments in the CESM ChangeLog file it sounds like tweaking co2vmr might not be a common practice in more recent versions of CAM. (There is a remark about it not being widely used from late 2016) I see that F2010climo uses a boundary layer file:
flbc_file = '$DIN_LOC_ROOT/atm/waccm/lb/LBC_2010climo_CMIP6_0p5degLat_c180227.nc'
which appears to be a year worth of monthly average concentrations. To get a new fixed CO2 concentration, would it be reasonable for me to create a second version of the flbc_file with M times the values from the original? Or would that give weird results for some reason? Alternatively, is there a way to get scenario_ghg = 'FIXED' to work with CAM6?
On a related note, i'm curious how the values from flbc_file are used in an F2010climo compset. Are these just replayed every year as-is for the length of the simulation? Or is there some time dependence (eg, maybe they are scaled up by some factor each year as the simulation progresses?) I'm hoping for the former, since otherwise my equilibrium simulation won't equilibrate. :)
Thanks!
-Rob
