Empirical Orthogonal Function Analysis of Hawaiian Rainfall

Empirical orthogonal function analysis was applied to monthly mean rainfall data at 63 stations in Hawaii encompassing a 37-year period. Major rainfall patterns in order to importance (E1–E3) proved to be trade wind, southwest wind and convective rainfall on an annual basis; trade wind, southwest wind and frontal rainfall during winter, spring and fall seasons; and trade wind, tropical disturbance and convective rainfall during summer. Trade wind rainfall (E1) explains most rainfall variance in summer and least variance in winter. Spectral analyses of the time-dependent coefficients for eigenvectors E1–E5 show annual, semi-annual, three-forths year, and 2–2½ year cycles. No spectral peaks relating to the 11- and 22-year sunspot cycles were found. Composite rainfall maps for wet and dry winter and summer half-years indicate the contributions that specific eigenvector patterns make to these anomalies. Comparisons between Hawaiian rainfall and E1 Ninos reveal that most (not all) E1 Nino winters in H...