NOy PEG

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 historical values for GHGs from the RCP scenarios defined for CMIP5
• 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
• The same lightning NOx routine were used by both models, and these were scaled to give approximately the same annual emissions

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.

Results

	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	Xjcir_eval_yr01.pdf Xjcir_eval_yr02.pdf Xjcir_eval_yr03.pdf Xjcir_eval_yr04.pdf Xjcir_eval_yr05.pdf Xjcir_eval_yr06.pdf Xjcir_eval_yr07.pdf Xjcir_eval_yr08.pdf Xjcir_eval_yr09.pdf Xjcir_eval_yr10.pdf	Xjcin_eval_yr01.pdf Xjcin_eval_yr02.pdf Xjcin_eval_yr03.pdf Xjcin_eval_yr04.pdf Xjcin_eval_yr05.pdf Xjcin_eval_yr06.pdf Xjcin_eval_yr07.pdf Xjcin_eval_yr08.pdf Xjcin_eval_yr09.pdf Xjcin_eval_yr10.pdf
NOy species time evolution	Xjcir_NOy.pdf	Xjcin_NOy_yr01-06.pdf
Comparison with SLIMCAT		Compare_SLIMCAT_UKCA.pdf
Lightning NOx	year 01 4.31451 Tg(N)/year year 02 4.14917 Tg(N)/year year 03 4.16817 Tg(N)/year year 04 4.17091 Tg(N)/year year 05 4.21050 Tg(N)/year year 06 4.15449 Tg(N)/year year 07 4.24399 Tg(N)/year year 08 4.16796 Tg(N)/year year 09 4.25567 Tg(N)/year year 10 4.19239 Tg(N)/year	year 01 3.93965 Tg(N)/year year 02 3.94823 Tg(N)/year year 03 4.00135 Tg(N)/year year 04 4.00217 Tg(N)/year year 05 3.96633 Tg(N)/year year 06 3.92943 Tg(N)/year year 07 4.02144 Tg(N)/year year 08 3.82724 Tg(N)/year

Minutes from meeting 2014-02-13

Present

Luke Abraham (NLA), Alex Archibald, James Keeble (JMK), Sandip Dhomse, Paul Griffiths, Martyn Chipperfield, John Pyle, Fiona O'Connor (skype)

Further experiments suggested

1. Change how the NOy species are treated: removed these from transform_halogen and make a new routine which also requires NO2 to be transported. The NOy (i.e. Lumped N) tracer is also advected and this is used as a test against the calculated NOy field from the individual species. Using this comparison the NOy species can be rescaled according to the ratio of $NO_{y}^{calculated}$ and $NO_{y}^{advected}$. BrONO2 and ClONO2 should not be rescaled as this would change the Cl and Br species. A diagnostic check on the differences between $NO_{y}^{calculated}$ and $NO_{y}^{advected}$ should be done, as well as possibly checking for global conservation during transport. The NALD tracer is not currently included and should be. (NLA to do)
2. Further to the above, try turning off all other processes and check the advection over a short run. Other steps could then be added piecewise to see their effects.
3. Check that N2O5 is not causing any problems by setting its rates to zero and set it to no_change in transform_halogen (JMK to do)