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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-2017-223
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
10 Aug 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).
A new method for estimating UV fluxes at ground level in cloud-free conditions
William Wandji Nyamsi1,2, Mikko R. A. Pitkänen2,3, Youva Aoun1, Philippe Blanc1, Anu Heikkilä4, Kaisa Lakkala4,5, Germar Bernhard6, Tapani Koskela7, Anders V. Lindfors2, Antti Arola2, and Lucien Wald1 1MINES ParisTech, PSL Research University, Centre Observation, Impacts, Energy, Sophia Antipolis, France
2Finnish Meteorological Institute, Kuopio, Finland
3Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
4Finnish Meteorological Institute, Climate Research, Helsinki, Finland
5Finnish Meteorological Institute, Arctic Research, Sodankylä, Finland
6Biospherical Instruments Inc., San Diego, California, USA
7independent researcher, Helsinki, Finland
Abstract. A new method has been developed to estimate the global and direct solar irradiance in the UV-A and UV-B, at ground level in cloud-free conditions. It is based on a resampling technique applied to the results of the k-distribution method and the correlated-k approximation of Kato et al. (1999) over the UV band. Its inputs are the aerosol properties, and total column ozone that are produced by the Copernicus Atmosphere Monitoring Service (CAMS). The estimates from this new method have been compared to instantaneous measurements of global UV irradiances made in cloud-free conditions at five stations at high latitudes in various climates. For the total or UV-A global irradiance, the bias ranges between −0.8 W m−2 (−3 % of the mean of all data) and −0.2 W m−2 (−1%). The root mean square error (RMSE) ranges from 1.1 W m−2 (6 %) to 1.9 W m−2 (9 %). The coefficient of determination R2 is greater than 0.98. The bias for UV-B is between −0.04 W m−2 (−4 %) and 0.08 W m−2 (+13 %) and the RMSE is 0.1 W m−2 (between 12 % and 18 %). R2 ranges between 0.97 and 0.99. This work demonstrates the quality of the proposed method combined with the CAMS products. Improvements, especially in the modelling of the reflectivity of the Earth's surface in the UV region, are necessary prior its inclusion into an operational tool.

Citation: Wandji Nyamsi, W., Pitkänen, M. R. A., Aoun, Y., Blanc, P., Heikkilä, A., Lakkala, K., Bernhard, G., Koskela, T., Lindfors, A. V., Arola, A., and Wald, L.: A new method for estimating UV fluxes at ground level in cloud-free conditions, Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2017-223, in review, 2017.
William Wandji Nyamsi et al.
William Wandji Nyamsi et al.
William Wandji Nyamsi et al.

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Short summary
This paper proposes a new, fast and accurate method for estimating UV fluxes at ground level in cloud-free conditions at any place and time. The method performs very well with the Copernicus Atmosphere Monitoring Service products as inputs describing the state of the atmosphere. The accuracy is reached that is close to the uncertainty of the measurements themselves. We believe that our research will be widely used in the near future.
This paper proposes a new, fast and accurate method for estimating UV fluxes at ground level in...
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