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difference between 'tracer_cnst_file' and 'prescribed_ozone_file'‏

S

szhu4@ncsu_edu

New Member
Hi,

I note that there are prescribed ozone data in 'tracer_cnst_file' and 'prescribed_ozone_file'.
So what the difference between these two prescribed ozone?

Thanks,
Shuai
 
E

eaton

CSEG and Liaisons
The tracer_cnst_file is used by the chemistry code. It may be used to provide prescribed oxidant concentrations, or it may be used for other species. The species provided by the tracer_cnst_file are set by the tracer_cnst_specifier variable. The prescribed_ozone_file is used to provide the ozone concentrations that affect the radiation calculations.

For example, the cam5 physics which includes prognostic modal aerosols uses the tracer_cnst_file to provide oxidants used in the aerosol chemistry calculations. But the concentrations of ozone that affect the radiation code come from the prescribed_ozone_file and are stored in the physics buffer with the name 'ozone'. The namelist variable rad_climate contains the specification that the constituent named 'ozone' in the physics buffer will provide the ozone values to the radiation code:

rad_climate = 'P_Q:H2O', 'D_O2:O2', 'D_CO2:CO2', 'D_ozone:O3', 'D_N2O:N2O', 'D_CH4:CH4', 'D_CFC11:CFC11', ...

The string 'D_ozone:O3' is decoded as follows: 'O3' is the name that the radiation code uses to identify ozone. The 'D' indicates that the source of the ozone concentration is the prescribed data contained in the physics buffer, and 'ozone' is the name used in the physics buffer.
 
C

chen63@illinois_edu

Member
Hi, Eaton,To continue this questions, I have noticed that in one of my simulations, the namelist variables in atm_in are as follows:  tracer_cnst_datapath           = '/project/projectdirs/PNNL-PJR/csm/inputdata/atm/cam/chem/trop_mozart_aero/oxid' tracer_cnst_file               = 'oxid_1.9x2.5_L26_1850-2005_c091123.nc' tracer_cnst_filelist           = 'oxid_1.9x2.5_L26_clim_list.c090805.txt' tracer_cnst_specifier          = 'O3','OH','NO3','HO2'  prescribed_ozone_datapath              = '/project/projectdirs/PNNL-PJR/csm/inputdata/atm/cam/ozone'  prescribed_ozone_file          = 'ozone_1.9x2.5_L26_1850-2005_c090803.nc'  prescribed_ozone_name          = 'O3' I checked the data of O3 in  tracer_cnst_file and prescribed_ozone_file are different. Does this mean that the concentrations of ozone that affect the radiation code are different from the concentrations used by the chemistry code? Could you explain a bit for me? Thanks a lot! Yanju
 
E

eaton

CSEG and Liaisons
Yes, the O3 from the tracer_cnst_file is used in the aerosol chemistry, and the O3 in prescribed_ozone_file is used by the radiation.I don't know why different ozone datasets are used for these two purposes.  I can only guess that the difference is not significant in a climate sense.  
 
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