SOME SOLAR-RADIATION STATISTICS FOR GREECE

The aim of this work is to provide solar radiation data for the whole Greek area. A series of daily measurements of global solar radiation on horizontal surfaces carried out during the period 1961-1988, in Athens, is analyzed first. The mean values for each climatic week show fluctuations in spring and autumn. Similarly, the decadic means of the total solar radiation show fluctuations in the spring and autumn. The absolute maximum values generally appear in June with the value 29.1 MJ m-2, and the minimum in December with the value 4.7 MJ m-2. We studied the elementary statistical characteristics and found that the interquartile range is small in winter and increases in spring and summer. The interannual variation of total radiation does not show any important trend. Fourier analysis of three representative stations radiation data was developed to obtain typical weekly and annual functions for direct calculation of the parameter. Similarly, harmonic analysis was applied to sunshine duration data from the same stations with excellent results. Furthermore, an estimate of the total solar radiation from climatological data in the Greek climatic area was carried out. The estimated values were compared with the corresponding measurements and in close agreement. Consequently, the results obtained can be used for heliotechnic purposes in places where a significant lack of radiation data exists.