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J.E.Williams, G-J van Zadelhoff, and P.F.J. van Velthoven

The Effect of Ice Particles on the Tropospheric Ozone Budget via Heterogeneous Conversion Processes. J.E.Williams, G-J van Zadelhoff, and P.F.J. van Velthoven. Outline of talk. Details of the chosen cirrus parameterization Physical properties of cirrus particles in TM4

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J.E.Williams, G-J van Zadelhoff, and P.F.J. van Velthoven

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  1. The Effect of Ice Particles on the Tropospheric Ozone Budget via Heterogeneous Conversion Processes J.E.Williams, G-J van Zadelhoff, and P.F.J. van Velthoven

  2. Outline of talk • Details of the chosen cirrus parameterization • Physical properties of cirrus particles in TM4 • Effects of adopting QUANTIFY 2050 air traffic emissions on atmospheric composition • Effects of Heterogeneous Conversion of the NO3 radical • Effects of reversible uptake of HNO3 • Missing components • Conclusions

  3. Effective radii : Fu(1996) (developed for GCM’s) Parameterizations for cirrus particles Cross-sectional area: Heymsfield and McFarquar(1996) • IWC values provided by ECMWF meterological data • Surface Area Density = scaling factor()*Ac • Physical properties: reff (cm-1), SAD (cm2/cm3)

  4. Parameterization of SAD derived by fitting a wide range of observations from CEPEX campaign. Previously applied in CTM studies: Lawrence and Crutzen (1998) Voh Kulmann and Lawrence (2005) Performance of Heymsfield + McFarquar (1996)

  5. Performance : Fu (1996) Comparison of Fu(1996) vs TRMM measurements Heymsfield, JAS, 2003

  6. Determination of the scaling factor for SAD The scaling factor can be selected considering the distribution of SAD with respect to IWC from measurements Previous values used in CTM studies Lawrence and Crutzen (1998) : 4 Von Kuhlmann and Lawrence (2005): 2 This study : 10 After Schmitt and Heymsfield (2005). Accounts for surface roughness of the ice. Popp et al, JGR, 2004

  7. Zonal distributions of ECMWF IWC and Reff in TM4 Coverage only updated every 6 hrs with ECMWF updates !!

  8. Difference in SAD between  values ƒ = 2 Tuned using details in L + C (1998) ƒ = 10

  9. Heterogeneous reactions on Ice Schwartz (1986) • Ice particles introduce reactive surface area upon which conversion processes may occur. • Characteristic  values for each chemical species measured in laboratory studies • Most CTM models include (clouds + aq aerosol): N2O5 (+H2O)  2HNO3  = 0.02 (ice) Other reactions involving nitrogen (Jacob, 2000) NO3 (+H2O)  HNO3  = 1e-3 (ice)

  10. Described by Langmuir Uptake (kabs/kdes) • [X]g ↔ [X]s Reversible uptake on Ice of N species Klang KLinC/Nmax kabs 0/4Nmax kdes0/ Klang4Nmax 0 = acc co-eff,  = mean molecular speed (cm-1 s-1), kabs scaled by SAD !!

  11. TM4 Model Description • 34 layers, 3 x 2 resolution • ECMWF meteorological data (6hrly updates) – incl. H2O • RETRO emissions w/ GFEDv2 biomass burning • Rate parameters updated to JPL 2006/IUPAC • Modified CBM4 mechanism (39 chemical species, 64 reactions, 16 photolysis reactions) • Full CH4-CO-NOx-HOx, C2+ Organics, ISOP, SO2, NH3 • Convection: Tietke, Advection: Russel and Learner • 3 month spin-up for each simulation Sensitivity tests Same ECMWF meteorology adopted throughout 2006 : Fixed T,p,winds,etc • BASE – Aircraft Emissions (RETRO 2000) - 48.5TgN yr-1 • BASE_2050 – QUANTIFY 2050 Aircraft Emissions - 52.5TgN yr-1 • NO3_UP – NO3 + ICE (ƒ = 2) • NO3_UP_HS– NO3 + ICE (ƒ = 10) • NO3_UP_HS_2050 – NO3 + ICE (ƒ = 10), QUANTIFY 2050 Aircraft Emissions • HNO3_UP – Reversible uptake of HNO3, QUANTIFY 2050 Aircraft Emissions

  12. Performance of the BASE run: UT 2006 MOZAIC in-flight data from Windhoek to Frankfurt (22.5°S, 13.5°E)

  13. Performance of the BASE run II: SHADOZ

  14. NH bias of effects in line with location of emission sources • Increase in [O3] in the mid troposphere associated with large increase in [NO2] • Associated increases in nitrogen radicals and reservoirs : [HNO3], [NO3], [N2O5] and [HNO4] • [BASE_2050]-[BASE]/[BASE] Effect of 2050 Future Aircraft Emissions: O3, NOx, HNO3

  15. Oxidizing capacity of the atmosphere increases • for fixed [CO] and [CH4] in line with [O3] • Increases in [OH] reach 30-40% in NH UT near largest [O3] • Small increases in [PAN] also contribute to [O3]  via long-range transport effects • [BASE_2050]-[BASE]/[BASE] Effect of 2050 Future Aircraft Emissions: CO, PAN, OH

  16. [OH]/[HO2] ratio increases • HOx precursors subsequently decrease in the UT • OH + HO2 • HO2 + HO2  H2O2 • HO2 + CH3O2  CH3O2H • [BASE_2050]-[BASE]/[BASE] Effect of 2050 Future Aircraft Emissions: CH2O, H2O2 and CH3O2H

  17. Budget : O3 production due to 2050aircraft emissionsBASE48.5TgN yr-1vsBASE_2050 53TgN yr-1(+9%) Burden:BASE 263TgO3 BASE_2050 282TgO3(+7%)

  18. BASE vs NO3_UP_HS Effect of NO3HNO3 on Ice : [O3], [NO3] BASE_2050 vs NO3_UP_HS_2050

  19. BASE vs NO3_UP_HS Effect of NO3HNO3 on Ice : [HNO3], [PAN] BASE vs NO3_UP_HS BASE_2050 vs NO3_UP_HS_2050

  20. Relative contribution to tropospheric [HNO3] Total Het Conversion increases with [NOx] Enhanced heterogeneous contribution when accounting for conversion of NO3 on cloud droplets !!

  21. NO3 (+H2O)  HNO3 • = 4e-3 (cloud) Higher  and SAD of cloud particles combine to enhance effect Low KH therefore phase transfer negligible Mimic of N2O5 approach in CTM’s (full conversion to HNO3) Effect of including Cloud surface reactions: [O3]

  22. BASE_2050 vs HNO3_UP : HNO3(g) ↔ HNO3(s) Effect of reversible uptake of HNO3 Relatively low range of SAD c.f. measurements in the CTM using the chosen parameterization limits uptake of HNO3. No chemical destruction or photolysis essentially enhances [HNO3] when integrated over the year For effect on [O3] there has to be a fraction of irreversible loss !!

  23. Comparisons with previous CTM studies Ratio [HNO3] Ratio [O3] Von Kulmann and Lawrence, ACP, 2005 This study cannot reproduce the ~40-60% uptake of HNO3 and decrease of ~4% in UT [O3]using a simple reversible equilibrium approach. No details of Nmax. Different Meteo (NCEP). No details of SAD coverage although identical parameterization used. 5.6 x 5.6 grid w/28 vertical levels.

  24. Efficiency of Uptake of HNO3 vs SAD Von Kulmann and Lawrence, ACP, 2005 We adopt recent IUPAC values (2009)

  25. Missing components in CTM • Large particles will sediment and deposit/evapourate thus de-nitrifying the UT. • Production of fresh surfaces/cirrus does not occur between ECMWF updates. • Fraction of [HNO3] buried in Ice (sink process) and converted to NO3- ?? • Competition of reactive sites from other species already attached

  26. ECMWF Zonal Annual Mean Temperature 2006 How correct is it to apply measurements between 210-240K in a global domain. Change in cirrus properties??

  27. Conclusions • Parameterizations have been included in a global CTM in order to introduce variable particle sizes and SAD based on IWC data input • Applying 2050 aircraft emission estimates increases [O3],[OH] in the UT over the NH subsequently alters the [OH]/[HO2] ratio. • Heterogeneous conversion of NO3 on cirrus perturbs tropospheric O3 by +1% (further enhanced by SAD of cloud droplets) • Reversible uptake of HNO3 has a limited effect compared to previous CTM studies possibly as a result of differences in SAD, uptake kinetics and resident [HNO3] • Dependent on the future variations in IWC due to Climate Change the role of heterogeneous chemistry has the potential to become more important under conditions where NOx emissions increase in the upper troposphere.

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