A spectral analysis of the 12-monthly running means of the global radi
ation ratio K-r observed at Wageningen (52 degrees N, 6 degrees E) sho
wed significant QBO, QTO (Quasi-biennial and Quasi-triennial Oscillati
ons) and higher periodicities, with the strongest peak at ca.22 years
but none at the solar cycle (11 years). All these are probably due to
similar periodicities in cloudiness. (C) 1997 by the Royal Meterologic
al Society.