The Link Between Changes in Ocean Surface Temperature and Rainfall in Hawai'i

Abstract

Hawaii's climate is shaped by a unique interaction of tropical ocean conditions, trade winds, and geomorphic effects that create distinct microclimates. This study investigates the influence of large-scale climate indices on Hawaii's rainfall patterns, including the Oceanic Nino Index (ONI) as an anomaly of sea surface temperature (SST), the Pacific Decadal Oscillation (PDO), and the Madden-Julian Oscillation (MJO). The study uses Pearson correlations to assess the relationships on different time scales, including lagged monthly data, 3, 6, and 12-month data. The results show that the linear correlation between the two climate indices, ONI and PDO, and rainfall in Hawaii is relatively weak at these time scales. However, when rainfall is stratified by positive and negative phases of ONI, PDO, and MJO, the phase-conditional means show strong differences ( 0-70 mm/month), indicating a clear nonlinear association. These findings suggest that when the data are analyzed through certain characterizations, ONI, PDO, and MJO exert a strong but nonlinear control on rainfall in Hawaii, and may be able to provide different phase-based benchmarks for future rainfall forecasts in the Hawaii region and for future model evaluations.