vn7.3 vs. vn8.4
While UKCA had low NOy at vn7.3, this feature has not improved when moving to vn8.2/vn8.4 GA4.0 jobs, and may even have become worse.
A pair of simulations have been set-up to try to aid the diagnosis of the cause of this low NOy. While there have been many changes to the base atmospheric model, the differences between the UKCA chemistry scheme used have been minimised.
- All surface and aircraft chemical emissions are the same between both jobs, and are year 2000 climatologies
- The SST/Sea-Ice ancillaries are daily means from the Reynolds dataset, and are meaned over 1995-2005
- All chemical reactions and associated rates are the same between both jobs
- The GHGs and tracer lower boundary conditions are the same for both jobs
- 2000-12-01 from the CCMI REF-C2 specification taking WMO2011 values for ODSs and following the RCP6.0 scenario (post 2005)
- The initial conditions of the chemical species are the same for both jobs, originally taken from a vn7.3 job. The winds and other physical initial conditions are different however
- Radiative feedback from O3 is included in both jobs
- vn8.4 job also considers radiative feedback from aerosols
NOTE: While the vn8.4 job does include GLOMAP-mode aerosols and some extra associated chemical reactions, the low NOy has also been observed in the vn8.2 CheST (only) configuration.
| VN7.3 | VN8.4 | |
| MONSooN jobid | xjcir | xjcin |
| Configuration | HadGEM3-A r2.0 | HadGEM3-A GA4.0 |
| Resolution | N48L60 | N96L85 |
| UKCA scheme | CheST | CheST+GLOMAP |
| Model set-up | TS2000 | TS2000 |
| Evaluation Suite Output |
|
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| NOy species time evolution |  Xjcir_NOy.pdf  |
Xjcin_NOy_yr01-06.pdf
|
| Comparison with SLIMCAT | Compare_SLIMCAT_UKCA.pdf
|
