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Testing the CBMhybrid chemical mechanism in TM5

Testing the CBMhybrid chemical mechanism in TM5. Jason Williams Chemistry & Climate Division, KNMI The Netherlands Contributions from : A. Strunk ; R Scheele. Motivation. CBM development (CB06).

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Testing the CBMhybrid chemical mechanism in TM5

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  1. Testing the CBMhybrid chemical mechanism in TM5 Jason Williams Chemistry & Climate Division, KNMI The Netherlands Contributions from : A. Strunk ; R Scheele

  2. Motivation

  3. CBM development (CB06) Yarwood et al, 9th annual CMAS conf., 2010

  4. TM5 chemistry versions Benchmark (modified CBM4) Huijnen et al, GMD 2010 Online photolysis (modified CBM4) Williams et al, GMDD, 2011 • Modified CBM4 • 29 transported tracers • 68 reaction rates • 18 photolysis rates • CBMhybrid • 39 transported tracers (+35%) • 101 reaction rates (+49%) • 21 photolysis rates (+17%) Online photolysis (CBMhybrid Scheme)

  5. Acetone in the CBM scheme OH + CH3C(O)CH3 (+ O2)  CH3C(O)CH2O2 HO2 + CH3C(O)CH2O2  ROOH CH3O2 + CH3C(O)CH2O2  0.5CH3OH + 0.5MGLY + 0.7HCHO + 0.5HO2 + 0.3CH3C(O)CH2OH + 0.2CH3C(O)O2 NO + CH3C(O)CH2O2  NO2+ CH3C(O)O2 + HCHO + HO2 NO2+ CH3C(O)CH2O2  MPAN CH3C(O)CH3 + hv  CH3C(O)O2 + CH3O2 (p,T dep) CH3C(O)CH3 + hv  CO + products 2 extra tracers, 5 reactions, 1 photolysis rate (2 channels) (Ignore MPAN formation to simplify system, NO3 reaction too slow) Still debate regarding the photolysis rate although JPL recommendation adopted in TM5

  6. Transported tracers Modified CBM4 CBMHybrid

  7. Sample surface distributions: Methanol and Terpenes Pre-dominantly biogenic sources with large annual fluxes (>100 Tg yr-1) Methanol emission covers ~90% of land Terpene emission over forested regions

  8. Sample surface distributions Anthropogenic and biomass burning sources for Propene Anthopogenic, BB and biogenic sources for Acetone Surface concentrations seem too low. Too high J values ?? (10-4 – 10-5 ) Lifetime of Acetone seems too short as very little leaves the boundary layer: Has been previously measured and modelled in the UTLS

  9. UTLS acetone concentrations: CARIBIC vs LMDz-INCA Elias et al, ACP, 2011 [acetone] ranges between 100-500 pptv at ~250hPa

  10. CO surface distribution • Surface [CO] ↑ 5-25%. • Near background stations ~10% increases. • Comparisons against CBM4 show that improvements would occur near VOC sources

  11. CO vertical distribution Significant under-prediction of CO in the Free Troposphere using the CBM4 mechanism CBMhybrid improves on this for the free troposphere

  12. O3 surface distribution : July 2001 Norway Netherlands Spain France

  13. O3 vertical distribution • Enhances O3 over-estimation at the summer in the boundary layer at global scale. • High differences in the Arctic troposphere during boreal summer • +10% differences in the TTL

  14. Differences in OH: July 2001 • Regional decreases over land; increases over ocean • Small increases in BL ; decreases in FT

  15. HOx reservoirs TM5 benchmark TM5 online photolysis SCIAMACHY Williams et al, GMDD, 2011

  16. NOx reservoirs • Large increases in PAN formation accounting for global increase in O3 • Also increases in HNO3 in large regions • Associated decreases in organic nitrate • Complex picture of changes in short-lived reactive nitrogen compounds

  17. Dampening of nightime oxidation • Large decreases in NO3 over the NOx source • regions. • Large increases over the oceans (associated with • extra PAN transport). • No changes in the J value between the • simulations ! • Loss principally due to repatitioning of reactive • nitrogen into PAN/HNO3. Will also affect N2O5 hydrolysis to HNO3

  18. Conclusions CBMHybrid integrated with online photolysis routine (explicit description of C1-C3 organic compounds included). Surface distributions of species seem ok. The lifetime of acetone appears too short. Reason (sink or source term) has yet to be determined. The global distribution of both CO and O3 increases in the order of ~5-20%. Coarse comparisions indicate over-estimations of both species in the chemical background at the surface. Improvements in CO in the free-troposphere. Significiant increases in both HOx and NOx reservoirs. Decreases in nightime oxidation over the land due to significant loss of the NO3 radical. Regional differences in OH distribution (lower over land). Version is currently participating in the Polar Multi-Model intercomparison (MACC II) Budget analysis needs to be performed and compared to that using modified CBM4

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