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Which fields in the atm output should I use

Eric

Eric
Member
Hello,

If I want to know atmospheric CO2 concentration, which field in the atm output files should I look into? There is a field called CO2, but it is a three-dimensional variable and is in the unit of kg/kg (I expect it to be in ppmv). If this is the field I should look into, is there an equation that I can use to transfer it to atmospheric CO2 concentration?

If I want to calculate global mean surface air temperature (2m air temperature), which field should I look into? I didn't find this field in the atm output but I found it in the land output. If I want to calculate the global mean, do I need to separately calculate land surface air temperature and ocean surface air temperature, and then average these two values? (Or simply, which field should I use to calculate global mean surface air temperature as calculated in CMIP6?)

If I want to know the simulated precipitation, should I look into the field "TMQ"? This is "total vertically integrated precipitable water" in the unit of Kg/m2, however, the precipitation that we usually use is in the unit of mm/m2. This is the only field that is relevant to precipitation so I kind of want to do a confirmation.

Thank you!!
 

strandwg

Member
Hello,

If I want to know atmospheric CO2 concentration, which field in the atm output files should I look into? There is a field called CO2, but it is a three-dimensional variable and is in the unit of kg/kg (I expect it to be in ppmv). If this is the field I should look into, is there an equation that I can use to transfer it to atmospheric CO2 concentration?

If I want to calculate global mean surface air temperature (2m air temperature), which field should I look into? I didn't find this field in the atm output but I found it in the land output. If I want to calculate the global mean, do I need to separately calculate land surface air temperature and ocean surface air temperature, and then average these two values? (Or simply, which field should I use to calculate global mean surface air temperature as calculated in CMIP6?)

If I want to know the simulated precipitation, should I look into the field "TMQ"? This is "total vertically integrated precipitable water" in the unit of Kg/m2, however, the precipitation that we usually use is in the unit of mm/m2. This is the only field that is relevant to precipitation so I kind of want to do a confirmation.

Thank you!!

You should have a field in your output called "co2vmr", which is the current CO2 value. It's a 1-D variable dimensioned only along time.

TREFHT is the 2m reference height temperature. There's also the field TS, which is the skin temperature calculated from the radiative fluxes.

The precipitation fields are PRECC, PRECL and PRECT - convective, large-scale and total precipitation, respectively.
 

Eric

Eric
Member
Hi Gary,

Thanks for the help. May I ask what the unit of co2vmr is? For example, now it shows me a value of 0.000399. How can I transfer it to the CO2 concentration in ppmv?

Regarding the temperature, which field do scientists use when they draw the global mean air temperature cure and analyze global warming?


Regarding the precipitation, I noticed that PRECC and PRECL are precipitation rates. If my atm output frequency is yearly average and I want to calculate the annual precipitation amount, should I multiply it with 365*24*60*60?

And there is no field called PRECT. Should I just add up PRECC and PRECL to get the total precipitation?

Thank you!!
 

strandwg

Member
Hi Gary,

Thanks for the help. May I ask what the unit of co2vmr is? For example, now it shows me a value of 0.000399. How can I transfer it to the CO2 concentration in ppmv?

Regarding the temperature, which field do scientists use when they draw the global mean air temperature cure and analyze global warming?


Regarding the precipitation, I noticed that PRECC and PRECL are precipitation rates. If my atm output frequency is yearly average and I want to calculate the annual precipitation amount, should I multiply it with 365*24*60*60?

And there is no field called PRECT. Should I just add up PRECC and PRECL to get the total precipitation?

Thank you!!

"co2vmr" is volume mixing ratio - multiply by 1.e6 to get PPM.

Usually "TS" is used for surface temperature.

All precipitation fields are in "m s-1" (meters per second) so if you sum and multiply by 86400 (seconds per year) you'll get total precipitation in meters.

PRECT is PRECC + PRECL, correct.
 
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