CAVIAR

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CAVIAR Continuum Absorption by Visible and
Infrared Radiation and its Atmospheric Relevance
PI Keith Shine Department of Meteorology,
University of Reading Co-Is Stephen Ball
Department of Chemistry, University of
Leicester Tom Gardiner National Physical
Laboratory Roderic Jones Department of Chemistry,
University of Cambridge John Harries, Juliet
Pickering Blackett Laboratory, Imperial College
London Kevin Smith Rutherford Appleton
Laboratory, STFC Jonathan Taylor and Stuart
Newman Met Office Jonathan Tennyson Department of
Physics, University College London Co-ordinator
Igor Ptashnik Dept of Meteorology, Univ of
Reading And (roughly!) 5 post-doc researchers and
3 PhD students
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We know

• Water vapour is by far the most important
  greenhouse gas in the atmosphere we know it is
  important for remote sensing we know it is an
  important contributor to climate feedbacks

We also know

• That it possesses a radiatively-important
  continuum, pervasive from the visible to
  microwave, which is represented in many models in
  a semi-empirical way, using observations from a
  limited number of wavenumbers and measurement
  conditions

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Major Aims

• Describe the continuum across a broad wavelength
  range and a broad range of atmospheric and
  near-atmospheric conditions, using both
  laboratory and field measurements
• Explain the underlying cause of the continuum
  can we separate out far-wing line shape
  contributions from dimer explanations?
• Provide the community with an improved continuum
  model (perhaps in a CKD-like form)

Measurements
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The Programme
WP1 Molecular Modelling
WP2 Laboratory Measurements
WP3 Field Measurements
WP4 Synthesis Everyone!
WP5 Impact on Understanding
WP6 Provision of model for wider use Everyone!
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The work flow
Work commenced
Work soon commencing!
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The Project

• Formally, we started on 1 October 2006 will
  formally end 30 June 2011 (including a no-cost
  extension)
• Annual meetings with international involvement

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Major progress in second year 1

• Development of a new potential energy surface for
  water dimer, which will allow improved ab-initio
  calculations of its spectra
• Analyses of new laboratory measurements to derive
  the continuum across the near-infrared

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Major progress in second year 2

• Advances in the broadband cavity-ringdown and
  cavity-enhanced methodologies and new results
• A major calibration exercise so that all CAVIAR
  field instrumentation are now traceable to the
  same standard

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Major progress in second year 3

• A major field campaign using aircraft and
  ground-based high-spectral resolution
  spectrometers, plus supporting data

Photo from Liam Tallis
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Challenges for third year 1

• Production of new ab initio dimer spectrum and
  comparison with measurements
• New laboratory measurements using both
  traditional FTS and cavity a particular
  emphasis will need to be on the between-band
  absorption, as this is most important for the
  AR in CAVIAR

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Challenges for third year 2

• Analysis of new laboratory measurements
• Full analysis of calibration of field instruments
• Full analysis of Camborne Field Campaign
• The second field campaign at Jungfraujoch in
  summer 2009

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Challenges for third year 3

• Begin serious work on the three remaining
  workpackages
• Synthesis of lab and field measurements and
  theoretical work
• Modelling the impact of the continuum on the
  radiation balance
• Developing a continuum model for community use

Clough et al. J.Geophys.Res, 1992
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Conclusions

• In Year 2, we have made significant progress in
  model and instrument development, acquired and
  analysed new laboratory data, performed the major
  Camborne field experiment, and have advanced
  plans for the Jungfraujoch 2009 campaign
• The legacy of the project
• - extensive new set of observations over a
  wide range of conditions in both lab and field
• - new physically-based continuum model with
  wide range of potential users in basic science,
  in weather and climate prediction and in remote
  sensing
• - cohort of post-docs and students trained in
  a cross-disciplinary environment