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Working Group-Ultraviolet Julian Gröbner and Mario Blumthaler.

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Presentation on theme: "Working Group-Ultraviolet Julian Gröbner and Mario Blumthaler."— Presentation transcript:

1 Working Group-Ultraviolet Julian Gröbner and Mario Blumthaler

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

3 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

4 ETS from various sources in the UV 15% Courtesy C. Gueymard

5 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 -> ±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)

6 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

7 Project: Traceability of solar UV radiation Time 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.

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