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The impact of changing HNO 3 formation in TM5-v4. J. E. Williams F. K. Boersma W. T. Verstraeten. Why the OH + NO 2 HNO 3 update ?. New measurement techniques allow all products to be measured simultaneously . OH + NO 2 + M HONO 2 (1a)
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The impact of changing HNO3 formation in TM5-v4 J. E. Williams F. K. Boersma W. T. Verstraeten
Why the OH + NO2 HNO3 update ? • New measurementtechniquesallowallproductstobemeasuredsimultaneously. • OH + NO2 + M HONO2 (1a) • HOONO (1b) • Recent laboratory measurements imply a slower rate of formation • than previously recommended (Mollner et al., Science, 2010) in • e.g. JPL 2011. • Henderson et al. used GEOS-chem and INTEX-A data to infer that an update to Mollner et al. (2010) is necessary at colder temperatures relevant to the UTLS. Adopts Evans and Jacob recommendations for N2O5 conversion on particles.
Vertical profiles of various K values Stavrakou et al., ACP, 2013
New IUPAC 2012 recommendation k0,1 = 3.2 x 10-30 (T/300)-4.5 [N2] cm3 molecule-1 s-1 over the temperature range 220 -300◦K k,1 = 3.0 x 10-11 cm3 molecule-1 s-1 over the temperature range 220-430◦K. Updated reaction co-efficients from Mollner, with theoretical extension by Tröe, as given in the IUPAC 2012 recommendations. Not based on CTM performance. c.f. Henderson values: k0,1 = 1.48 x 10-30 (T/300)-1.8 [N2] cm3 molecule-1 s-1 over the temperature range 220 -300◦K k,1 = 2.58 x 10-11 cm3 molecule-1 s-1.
TM5 v4 model set-up CBM4-Online J MACCity (Anthropogenic) MEGAN-MACC (Biogenic) GFEDv3 (Biomass Burning) New nudging versus ODIN climatology in the stratosphere for HNO3 and CO. New heterogeneous chemistry rates (over-estimated) Simulations: BASE, HEND and IUPAC
Effect on zonal HNO3 formation: January • Contrasting behaviour between Henderson update and the kinetic data provided by IUPAC. • Effects in the middle troposphere limited to ±2% • Largest effects of 10-25% occur in the tropical trop. • Impact of Henderson rate parameters agrees with the changes discussed in their paper. • Total uncertainty: • 35% UTLS • 5% MT
Effect on zonal HNO3 formation: July • Contrasting behaviour between robust across seasons. Maximum relative difference is lower for boreal summertime. • Largest effects of 5-10% occur in the tropical troposphere. • Seasonal cycle in magnitude of the differences in both rate • recommendations. • Total uncertainty: • 20% UTLS • 5% MT
Effect on near-surface HNO3 : January • Opposite behaviour near strong source regions. • Strong temperature sensitivity: • Total uncertainity = 30%
Effect on near-surface HNO3 : July • High photochemical activity with corresponding high T. Less efficient formation with HEND. • Seasonal cycle exists in the relative differences: out of phase when comparing HEND and IUPAC
Effect on zonal O3 formation: January • Divergent behaviour on composition between different recommendations. • Changes in surface mixing ratios of O3 of between 2-10%. This introduces differences in the oxidative capacity and, thus, chemical lifetimes.
Effect on zonal PAN formation: January • More transport of PAN throughout the tropopshere in HEND contributes to global increase in tropopsheric O3 (i.e. SH). • Opposite effect seen when using IUPAC
Effect on zonal CO formation: January • Changes in zonal O3 distribution result in associated changes in the CO distribution due to changes in oxidative capacity, thus lifetime. • Changes in surface mixing ratios between 2-10% (HEND) or 2-5% (IUPAC).
Lifetimes and Burden changes (2006) Relative robust when looking at loss of N
Global NOx recycling (BL) Change in global HNO3 production in BL more enhanced when using IUPAC updates.
Global NOx recycling (UTLS) Change in global HNO3 production in UTLS equal, but opposite, between rates.
Effect on near-surface NO2: July • Changes in near-surface NO2 mixing ratios are limited to ppt levels near the main source regions . • Uncertainty with respect to satellite retrievals comes mainly from changes in vertical column rather than changes in the footprint.
Conclusions • There is divergent behaviour between the tuned rate of Henderson et al. (2012) and the recommendations from IUPAC (2012), especially in the UTLS. Essentially the vertical changes are simular but of an opposite sign (increases versus decreases). • The magnitude of the changes is higher during boreal wintertime. • In general there are changes of between 2-10% for O3 and 2-5% for CO. • Transport of N out of source regions most effective in HEND. • The largest differences in O3 production terms between rates occurs in UTLS. • CB05 : Are the changes as large ?? 1x1 impact ??.