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Changing CO2 Values



I am planning on simulating paleoclimate conditions. Therefore I need to change CO2 values. I am using the CAM radiation scheme. Does the model retrieve the CO2 values from lines 302-344 depending on the simulation year? If so, do I need to do anything beyond changing the CO2 values within that range to match the CO2 concentration I want the model to use? Also, are there similar locations to change other GHG values, or can you only manually adjust CO2? Finally, as it is an atmosphere model and forced by surface conditions, I assume no orbital parameters need to be adjusted. Is that assumption also correct, and are there any other adjustments that need to be considered when conducting a paleoclimate or EOC simulation? Thank you for your continual assistance.



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How to modify CO2 value depends on the gig_input option.

(1) If this option is activated, then you need to modify the code "phys/module_ra_clWRF_support.F", in which annual CO2 values for the period 1869-2102 are specified. The model will read these data, interpolate to the time of model run. For your paleoclimate study, you need to change the values based on your study period.

(2) If the ghg_input option is not activated, then co2 value is specified in phys/module_ra_cam.F. The line below gives co2 value.
co2vmr = (co2(nyrm)*fact1 + co2(nyrp)*fact2)*1.e-06

(3) depending on the study period of paleoclimate, orbital parameters may need to be changed. I am not an expert in this field, and this is just based on why understanding of the paleoclimate simulation. Please refer to the literature for more information.

Sorry that I mistaken your model as WRF. MPAS doesn't have the namelist option ghg_input, instead, it employs the method similar to that in WRF with ghg_input = 0, i.e., the option (2) in my previous post. Note that the CO2 values for the period 1869-2102 are provided. if your paleoclimate simulation is over a period before 1869, you need to modify the values and codes to make it consistent with your study period.