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Questions on O3S(Stratospheric Ozone Tracer) calculation

Jinfly

New Member
Dear Community,

I run a CESM2.2.0 case with FCSD compset during 1980-2022. The resolution is 0.9°*1.25° with 56 vertical levels. The meteorological field is nudged to MERRA2 and CMIP6 historical emissions are used. I want to analyse the contribution of STT (Stratosphere-to-Troposphere Transport) in tropospheric ozone based on the O3S (stratospheric ozone tracer) variable. By definition, O3S is set to be the same as O3 above tropopause, and undergoes the same loss and diffusion rate as O3 below the tropopause, but no production. So the value of O3S should always be less than O3 in troposphere.

However, I find in specific situations the value of O3S is higher than O3 in the simulation. It sometimes occurs in areas with high anthropogenic emissions (i.e. eastern China cities), especially in winter. This phenomenon originates from the lowest model level and can extend up to 4 levels above.

I wonder what causes this phenomenon and whether it is a special case.

I would greatly appreciate any suggestions.

Best regards,
Jinfly
 
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