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Volume 10, issue 12 | Copyright
Atmos. Meas. Tech., 10, 4965-4978, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 19 Dec 2017

Research article | 19 Dec 2017

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 William Wandji Nyamsi et al.
  • 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 UV-A irradiance, the bias ranges between −0.8Wm−2 (−3% of the mean of all data) and −0.2Wm−2 (−1%). The root mean square error (RMSE) ranges from 1.1Wm−2 (6%) to 1.9Wm−2 (9%). The coefficient of determination R2 is greater than 0.98. The bias for UV-B is between −0.04Wm−2 (−4%) and 0.08Wm−2 (+13%) and the RMSE is 0.1Wm−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 modeling of the reflectivity of the Earth's surface in the UV region, are necessary prior to its inclusion into an operational tool.

Publications Copernicus
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. An accuracy that is close to the uncertainty of the measurements themselves is reached. 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...