Atmospheric Chemistry

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Atmospheric Chemistry Climate

• UK Earth System Modelling and the QUEST Project

Paul Young QUAAC Project Coordinator, Centre for
Atmospheric Science, University of Cambridge
UK-China Workshop, Reading, 29th Jul 2008
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MotivationWhy an Earth-System Approach for
Atmospheric Chemistry?
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(No Transcript)
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Atmospheric Chemistry (gas)
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Why the interest in BVOCs?
Reactive
methane (?), ethene, acetone,
isoprene, a-pinene, b-caryophylene
Aerosols
T, light, H2O, CO2, species, nutrients
Anthropogenic land use change
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Isoprene
James Ryder (CEH) / Sue Owen (CREAF)
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QUEST QUAAC Projects
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What is QUEST?

• Quantifying and Understanding the Earth SysTem
• Multi-million NERC-funded program
• HQ University of Bristol, head Prof Colin
  Prentice

Theme 1
Theme 2
Theme 3
Long-term natural regulation of climate
composition
Global environment change sustainable resource
use
Contemporary C-cycle chemistry climate
Cross-Cutting Activities
e.g. QUEST Earth System Model
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What is QUAAC?

• QUest Aerosols and Atmospheric Chemistry
• 4 Science Components
• Atmospheric Chemistry (Leeds, Cambridge)
• Aerosol Scheme (Leeds, Manchester)
• Biogenic Emission Scheme (Lancaster, Sheffield)
• Deposition Scheme (CEH)
• Build on UKCA model integrate into QESM
• QUAAC PI Prof John Pyle, Cambridge

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Gas-phase chemistry

• Three schemes being developed
• Simple Centennial-scale runs (QESM)
• Intermediate standard simulations (1-10yrs)
• Complex Short (months) or longer nested runs
• All involve simplifications
• Need to couple with aerosol (K. Carslaw talk)

Mat Evans and Kathryn Emmerson, University of
Leeds
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Secondary Organic Aerosol
No Isoprene
With Isoprene
Surface
5 km

• Henze and Seinfeld, 2006

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SOA Chemistry in QUAAC
Anthropogenic and Biogenic precursor molecules
Average of many structures to give gas-aerosol
partitioning characteristics

• Mark Barley and Gordon McFiggans, University of
  Manchester

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Modelling NH3 Bi-Directional Fluxes
Function of RH and SO2/NH3
What controls stomatal compensation point, Gs?
- Plant species - N status - Growth stage
Mhairi Coyle and Eiko Nemitz, CEH
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QESM Schematic
Atmospheric chemistry aerosols
Atmospheric physics dynamics
HadGAM1a
Ocean physics, biology sea ice
Land processes
Led by Manoj Joshi, Univ. Reading. See
http//www.quest-esm.ac.uk
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QESM Schematic
Atmospheric chemistry aerosols
Atmospheric physics dynamics
HadGAM1a
Ocean physics, biology sea ice
Land processes
Led by Manoj Joshi, Univ. Reading. See
http//www.quest-esm.ac.uk
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Some Chem/Clim Experiments
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Chemical Footprints - HTAP

• Hemispheric Transport of Atmospheric Pollution
• Impact of pollution from Region A on Region B
• Look at ozone, particles, POPs, Hg, acids
• Source-Receptor experiments (multi-model)
• http//www.htap.org

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20 reduction in European NOx
Guang Zeng, University of Cambridge and the HTAP
Community
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20 reduction in east Asian NOx
Guang Zeng, University of Cambridge and the HTAP
Community
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20 reduction in south Asian NOx
Guang Zeng, University of Cambridge and the HTAP
Community
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Footprint of Asia/Oceania isoprene
?O3 / ppbv
25 reduction in January isoprene
Young, Unpublished 2006
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Future Atmospheric Composition?

• Depends on
• Anthropogenic emissions
• Biogenic emissions
• Climate
• Make sequential changes to look at each effect
• Caution! Chemistry is non-linear

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Pessimistic 2100 (A2) East Asia
Boundary layer ozone changes (ppbv)
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Isoprene and CO2 A new puzzle?
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Including CO2 inhibition of isoprene
?O3 / ppbv July
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How important is the CO2 effect for 2100 A2?
Surface Ozone July
(wCO2 noCO2) / (noCO2 Present day)

Young et al. submitted
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Summary

• Many relevant atmospheric modelling studies
  completed/underway
• Application of ESM to this region desirable (post
  OP3)
• Wide variety of growth scenarios makes east Asian
  chemistry interesting
• as well as proximity to biogenic sources (inc.
  land use change)
• Chem/Clim monsoon-chemistry links as well as the
  future

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Useful www links

• QUEST http//quest.bris.ac.uk
• QUAAC http//researchpages.net/QUAAC
• QESM http//www.quest-esm.ac.uk
• UKCA http//www.ukca.ac.uk
• HTAP http//www.htap.org

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Atmospheric chemistry of BVOCs
Tropospheric ozone is chemically produced in the
presence of sunlight, NOx and VOCs
Isoprene is very reactive and will also reduce OH
concentrations (impact methane lifetime etc.)
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Atmospheric chemistry of BVOCs
Larger VOCs can complicate the cycle by
sequestering NOx

• Production of organic nitrate competes with
  oxidation of NO
• Branching ratio for isoprene nitrate (ISON) is
  uncertain 4.5 15

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Atmospheric chemistry of BVOCs
Larger VOCs can complicate the cycle by
sequestering NOx
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Atmospheric chemistry of BVOCs
In the absence of NOx soluble hydroperoxides are
formed which may be a sink for HOx radicals
If we change BVOC emissions, what is the impact
on tropospheric composition?