Working Group-Ultraviolet

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Working Group-Ultraviolet

• Julian Gröbner and Mario Blumthaler

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Scientific Objectives

• Open issues with regard to surface UV radiation
• Reference extraterrestrial solar spectrum (ETS)
  with high resolution
• Spectral aerosol optical depth (AOD) retrieval

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Scientific Objective ETS

• - UV Modelling studies using ETS show systematic
  spectral features which are a clear indication of
  features in ETS spectra. This currently limits
  the interpretation of UV measurement and
  Modelling studies (examples surface albedo and
  atmospheric composition studies, ).

Courtesy G. Bernhard, 2006
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ETS from various sources in the UV
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Courtesy C. Gueymard
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Scientific Objective Spectral AOD

• Retrieval of spectral AOD is obtained from direct
  sun irradiance spectra.
• Current limitations are
• - Total column ozone is necessary to remove
  ozone absorption
• Inconsistences in ozone x-sections and TOC
  retrievals by various instruments (Brewer,
  Dobson, Satellites)
• 3 TOC uncertainty -gt 0.10 at 300 nm
• The WMO goal for AOD determination is 0.01
• This problem is under investigation (ICAGO-O3
  Activity, WMO ozone theme meeting, 2010)
• - Reference ETS
• Cannot be obtained from standard Langley
  technique (Even Resolution of 0.5nm leads to
  systematic effects due to steep absorption of
  ETS)

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WG UV proposed activities

• Address these objectives through
• Sessions at Conferences (i.e. IAMAS 2011 in
  Melbourne)
• Discussions and coordinated approach by the UV
  Community
• Consider a IRC UV Newsletter Upcoming
  Conferences, recent publications, new and ongoing
  projects, project calls,
• Further activities
• Promote Instrument developments for surface UV
  measurements
• Supporting projects

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Project Traceability of solar UV radiationTime
frame 2011-2013

• Project Proposal to improve solar UV
  spectroradiometry by
• New reference standards
• Improved instruments
• Well characterised array spectradiometers
• Activity is embedded in the European Metrology
  Research Programme (EMRP) of EURAMET and the EU
  (Call 2010)
• To reach uncertainties of the order of 1-2 -
  Currently 5 is state-of-the-art
• A Letter of expression of support from the IRC
  will strengthen the project submission and
  demonstrate the support from the radiation
  community.