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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/amt-2017-171
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
20 Jun 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).
Temperature dependence of the Brewer global UV measurements
Ilias Fountoulakis1, Alberto Redondas2, Kaisa Lakkala3,5, Alberto Berjon2, Alkiviadis F. Bais1, Lionel Doppler4, Uwe Feister4, Anu Heikkila5, Tomi Karppinen3, Juha M. Karhu3, Tapani Koskela5,*, Katerina Garane1, Konstantinos Fragkos1,6, and Volodya Savastiouk7 1Aristotle University of Thessaloniki, Laboratory of Atmospheric Physics, Thessaloniki, Greece
2Agencia Estatal de Meteorología, Izaña Atmospheric Research Center, Spain
3Finnish Meteorological Institute – Arctic Research Centre, Sodankylä, Finland
4Deutscher Wetterdienst, Meteorologisches Observatorium Lindenberg – Richard Assmann Observatorium (DWD, MOL-RAO)
5Finnish Meteorological Institute, Climate Research, Helsinki, Finland
6National Institute of R&D for Optoelectronics, Magurele, Romania
7International Ozone Services Inc, Toronto, Canada
*works now as independent researcher
Abstract. Spectral measurements of global UV irradiance recorded by Brewer spectrophotometers can be significantly affected by instrument-specific optical and mechanical features, thus proper corrections are needed in order to reduce the associated uncertainties to within acceptable levels. The present study aims to contribute to the reduction of uncertainties originating from changes in the Brewer’s internal temperature, which affect the performance of the optical and electronic parts, and subsequently the response of the instrument. Until now, measurements of the irradiance from various types of lamps at different temperatures are used to characterize the instruments’ temperature dependence. The use of 50 Watt lamps was found to induce errors in the characterization due to changes in the transmissivity of the Teflon diffuser as it warms up by the heat of the lamp. In contrast the use of 200 or 1000 Watt lamps is considered more appropriate because they are positioned at longer distances from the diffuser so that warming is negligible. Temperature gradients inside the instrument can cause mechanical stresses which can affect the instrument’s optical characteristics. Therefore during the temperature-dependence characterization procedure warming or cooling must be slow enough to allow all parts of the instrument to be nearly equilibrated. In this study, results of the temperature characterization of eight different Brewer spectrophotometers operating in Greece, Finland, Germany and Spain are presented. It was found that the instruments’ response is changing differently in different temperature regions due to different responses of the diffusers’ transmittance. The temperature correction factors derived for the Brewer spectrophotometers operating at Thessaloniki, Greece and Sodankylä, Finland were evaluated and were found to remove the temperature dependence of the instruments’ sensitivity.

Citation: Fountoulakis, I., Redondas, A., Lakkala, K., Berjon, A., Bais, A. F., Doppler, L., Feister, U., Heikkila, A., Karppinen, T., Karhu, J. M., Koskela, T., Garane, K., Fragkos, K., and Savastiouk, V.: Temperature dependence of the Brewer global UV measurements, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2017-171, in review, 2017.
Ilias Fountoulakis et al.
Ilias Fountoulakis et al.
Ilias Fountoulakis et al.

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Short summary
Results of the temperature characterization of the global UV spectral measurements of eight different Brewer spectrophotometers operating in Greece, Finland, Germany and Spain are presented. Different temperature characterization methods are evaluated and an improved methodology for the correction of the measurements for the effects of temperature is presented.
Results of the temperature characterization of the global UV spectral measurements of eight...
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