Assessment of the method used to construct clearness index maps for the new European Solar Radiation Atlas (ESRA)

We present an assessment of the methods used to construct maps for a new solar radiation atlas for Europe. For this atlas, station data and satellite-derived data are used in an interpolation/merging process to derive maps of the long-term monthly global radiation that cover an area ranging from 30° W to 70° E and from 25° to 75° N. Our focus is on the discussion of the accuracy of the method applied: a co-kriging technique. Special emphasis is put on a discussion as to whether the use of satellite-derived radiation maps with a low spatial resolution brings benefits.