Periodic (18.6‐year) and cyclic (11‐year) induced drought and flood in western North America

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Abstract
Analysis of 102 recent tree‐ring chronologies confirms earlier evidence for 18.6‐year tidal drought/flood induction (Currie, 1981d, 1984b) and led to discovery of 11‐year solar cycle induced drought/flood for western North America. Bistable phasing in terms of geography is found with epochs of maximum in lunar nodal 18.6‐year drought in western Canada out of phase with those in the western United States and northern Mexico the past two centuries. Solar drought/flood induction provides one mechanism that appears to have modulated the intensity of nodal drought/flood induction in the latter region, most recently at epoch 1936.1. The above results were confirmed by analysis of yet more voluminous data, and they led to discovery of an example of bistable phasing with respect to time in western Canada during the 17th century. The implications for agriculture of such phenomena, which occur world‐wide (Currie, 1984c), are surveyed.