Hello, I am looking to calculate the MOC strength and a colleague recommended that there may be an output variable that can be enabled through the namelist that quantifies AMOC strength as an already defined output of the model. After looking through the namelist for the ocean variables I can't quite find such a variable--does anyone know of a variable that would fit this description? Thanks!
Finding an output variable to enable to calculate MOC strength
Hi Josh,
The POP variable you are looking for is MOC. For AMOC you want to use the transport_reg 2 (1 refers to the global meridional overturning circulation).
Typically, when looking at AMOC strength we look at the maximum of the overturning stream function below 500 meters.
Hope this is helpful.
Fred
The POP variable you are looking for is MOC. For AMOC you want to use the transport_reg 2 (1 refers to the global meridional overturning circulation).
Typically, when looking at AMOC strength we look at the maximum of the overturning stream function below 500 meters.
Hope this is helpful.
Fred
Thanks Fred, this is really helpful!
The issue I’m running into now is what POP history file has the MOC variable output. I’ve been looking for a bit and can’t seem to find it—is the MOC variable output by default or does it have to be enabled in the build?
Thanks, Josh
The issue I’m running into now is what POP history file has the MOC variable output. I’ve been looking for a bit and can’t seem to find it—is the MOC variable output by default or does it have to be enabled in the build?
Thanks, Josh
aneeshcs@gmail_com
New Member
Hi Fred,
Thanks very much for the reply! Josh is a student in my climate modeling class at CU. He wants to run his own simulation using the B1850 compset of CESM2 with preindustrial and 4X CO2 forcing. He has run some short B1850 simulations with Cecile's CESM tutorial to learn to run CESM2 (< 1 year), and we looked at his ocn output history files and couldn't find the MOC variable in these output files. We also looked at some 5-year-long CESM2 integrations from a different student and did not find MOC variable in the ocn history files. We were able to find the moc_z variable in the monthly history files from this CESM2 run but no variable called MOC itself.
Do you have any sample CESM2 output history files with the MOC variable saved that he can test making plots from while he waits for his CESM2 simulations to be completed?
Thanks,
Aneesh
Thanks very much for the reply! Josh is a student in my climate modeling class at CU. He wants to run his own simulation using the B1850 compset of CESM2 with preindustrial and 4X CO2 forcing. He has run some short B1850 simulations with Cecile's CESM tutorial to learn to run CESM2 (< 1 year), and we looked at his ocn output history files and couldn't find the MOC variable in these output files. We also looked at some 5-year-long CESM2 integrations from a different student and did not find MOC variable in the ocn history files. We were able to find the moc_z variable in the monthly history files from this CESM2 run but no variable called MOC itself.
Do you have any sample CESM2 output history files with the MOC variable saved that he can test making plots from while he waits for his CESM2 simulations to be completed?
Thanks,
Aneesh
Hi Aneesh and Josh,
As I said MOC is usually a default variable in all nominal 1 degree CESM runs. I guess the tags created for the tutorial has reduced output streams to make it cheaper to run...
Could you check your the POP namelist file (pop_in) in your $RUNDIR. Specifically, check in transports_nml to see if moc_requested is set to true. I expect it to be false since you are not getting the MOC variable in your POP tavg files.
To fix this you will need to use user_nl_pop in your $CASEROOT directory. Just edit the file with your favorite text editor and add the following lines in it:
&transports_nml
lat_aux_begin = -90.0
lat_aux_end = 90.0
lat_aux_grid_type = 'southern'
moc_requested = .true.
n_heat_trans_requested = .true.
n_lat_aux_grid = 180
n_salt_trans_requested = .true.
n_transport_reg = 2
transport_reg2_names = 'Atlantic Ocean', 'Mediterranean Sea', 'Labrador Sea', 'GIN Sea', 'Arctic Ocean', 'Hudson Bay'
Next time you run the model, the POP tavg file should contain the variable MOC, N_HEAT, and N_SALT.
Note that if you are doing a continue run, you may have to create a branch or start a new case since CESM doesn't allow changes the output streams during a continue run.
Thanks Gary for sharing MOC datasets!
Fred
As I said MOC is usually a default variable in all nominal 1 degree CESM runs. I guess the tags created for the tutorial has reduced output streams to make it cheaper to run...
Could you check your the POP namelist file (pop_in) in your $RUNDIR. Specifically, check in transports_nml to see if moc_requested is set to true. I expect it to be false since you are not getting the MOC variable in your POP tavg files.
To fix this you will need to use user_nl_pop in your $CASEROOT directory. Just edit the file with your favorite text editor and add the following lines in it:
&transports_nml
lat_aux_begin = -90.0
lat_aux_end = 90.0
lat_aux_grid_type = 'southern'
moc_requested = .true.
n_heat_trans_requested = .true.
n_lat_aux_grid = 180
n_salt_trans_requested = .true.
n_transport_reg = 2
transport_reg2_names = 'Atlantic Ocean', 'Mediterranean Sea', 'Labrador Sea', 'GIN Sea', 'Arctic Ocean', 'Hudson Bay'
Next time you run the model, the POP tavg file should contain the variable MOC, N_HEAT, and N_SALT.
Note that if you are doing a continue run, you may have to create a branch or start a new case since CESM doesn't allow changes the output streams during a continue run.
Thanks Gary for sharing MOC datasets!
Fred
aneeshcs@gmail_com
New Member
Thanks very much, Gary and Fred! This is very helpful. I think we can get what Josh wants from here.