Evidence for 18.6‐year lunar nodal drought in western North america during the past millennium

Abstract

Analysis of 38 tree ring chronologies yields evidence for enhanced drought conditions every 18.6 years in the North American interior for the past millennium. Cross spectra between a drought area index and 26 temperature records confirm the analysis of Currie (1979, 1981d) as regards a lunar nodal M N term in these data. Discussion of the M N tidal constituent, which appreciably modulates amplitude and phase of four main constituents (M 2 , K 1 , O 1 , M f ) is presented, and implications for agriculture are surveyed.