Estimating daily sunshine duration over Belgium by combination of station and satellite data

As more and more meteorological stations are working in a fully automatic mode, the classic Campbell–Stokes instrument for measuring sunshine duration becomes obsolete. As a consequence, in situ observations of daily sunshine duration over Belgium become sparse and require extensive interpolation to produce spatially complete fields. Two different approaches combining ground station and geostationary satellite data to estimate daily sunshine duration over Belgium at the satellite pixel level are evaluated here. The analysis uses solar radiation parameters retrieved from Meteosat Second Generation (MSG) data. Efficiency of each approach, i.e. the degree of closeness between the estimated and measured values, is evaluated by means of statistical error indices. The best performance is obtained when combining data from in situ measurements of sunshine duration (i.e. at stations) with a MSG-based clearness index (i.e. at the MSG pixel scale).