A SERIES OF GLOBAL RADIATION AT WAGENINGEN FOR 1928-1992

A series of daily total incoming radiation measured at Wageningen, The Netherlands, for the period 1928-1999 is described. These data are pr esented as relative global radiation (K-r), which is defined as the gl obal radiation divided by the corresponding extraterrestrial value. Bo th the year-to-year variation and the mean annual cycles of K-r averag ed over a year, season, month, decade (10 days), and a day are conside red. Also, frequency distributions are evaluated. It is found that the maximum of K-r does not occur in June, when the solar elevation is hi ghest, but in May. This is due partly to the west European monsoon, ca using a decline of K-r in the last decade of June and second decade of July. Also, it is found that 'sunny' weather (K-r relatively large) a ppears to be significantly persistent in May especially. The persisten ce of 'cloudy weather' (K-r relatively small) is less pronounced.