LUNI-SOLAR 18.6-YEAR AND 10-11-YEAR SOLAR-CYCLE SIGNALS IN LAMB,H.H. DUST VEIL INDEX

Maximum entropy and Yule-Walker methods of spectrum analysis applied to Lamb's dust veil indices (dvi) for the Northern Hemisphere (1500-1968) show two strong peaks, with periods of 18.6+/-0.5 and 10.8+/-0.3 years. They are identified as the 18.6-year luni-solar M(n) and 10-11-year solar cycle S(c) signals, which have recently been reported in a wide variety of climate and economic time series. The signals were transformed into the time domain by band-pass filters, their wavetrains summed, and the sum superimposed on trend-like components of the dvi; it is found that they account for 48 per cent of variance in the index.