Project Objectives

The Joint Research Project "Traceability for surface spectral solar ultraviolet radiation" is a collaboration between National Metrology Institutes, partners from Industry and the research Community in Europe.

This project will significantly enhance the reliability of spectral solar UV radiation measured at the Earth surface by developing new methods of observation (techniques and instruments) to provide traceable solar UV irradiance measurements with an uncertainty of less than 2%.

The activity is essential to unambiguously quantify decadal changes in solar UV radiation due to the expected changes in the global climate system. The project will address these objectives by shortening the traceability chain of the solar UV measurements to the SI unit and to reduce the associated transfer uncertainties. The goal is to approach uncertainties in the field comparable to those currently achieved only for primary spectral irradiance scale realisations at NMI level, i.e., at the level of 1%.

Planned work

To achieve the objective of providing traceable solar UV irradiance measurements with an uncertainty of less than 2%, the European reference spectroradiometer QASUME will be fitted with an improved global entrance optic and newly developed solid state detectors. New portable transfer standards will be developed to transfer the irradiance scale from the primary standard of spectral irradiance held at NMI facilities to spectral solar irradiance measurements.

In view of using cost-effective array spectroradiometers as replacements for current UV filter Radiometers in UV monitoring networks, significant progress needs to be achieved in the characterisation of these devices. New characterisation techniques and post-correction methods will be developed to determine and correct the stray light, linearity, and wavelength scale of array spectroradiometers. These activities will be supported by designing and constructing novel array spectroradiometers with improved stray light characteristics based on band pass filters and micro-electro-mechanical systems (e.g. MEMS and DLP).

The dissemination of the improved irradiance traceability and the demonstration of the tools and methods developed in this project will occur by a large field intercomparison of spectroradiometers at the World Radiation Center, Davos, Switzerland. Participants from the end-user community involved in solar UV measurements will be invited to this field intercomparison. Participating spectroradiometers from the end-users will be characterised and calibrated by the facilities developed in this JRP to provide traceability of spectral solar UV irradiance at this new level of uncertainty to the wider European UV monitoring community. The prototype devices developed in the JRP will be commercialised and the methodologies freely disseminated to create a sustainable basis for improved solar UV measurements in regional and national UV monitoring networks.



Users from the solar UV community will be involved in the project through the following activities:


The research leading to these results has received funding from the European Union
on the basis of Decision No 912/2009/EC.