a new method for estimating uv fluxes at ground level in cloud-free conditions
;W. Wandji Nyamsi;W. Wandji Nyamsi;M. R. A. Pitkänen;M. R. A. Pitkänen;Y. Aoun;P. Blanc;A. Heikkilä;K. Lakkala;K. Lakkala;G. Bernhard;T. Koskela;A. V. Lindfors;A. Arola;L. Wald
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 −0.8 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 modeling of the reflectivity of the Earth's surface in the
UV region, are necessary prior to its inclusion into an operational tool.