Month-Year Rainfall Maps of the Hawaiian Islands

Abstract

The Hawaiian Islands have one of the most spatially-diverse rainfall patterns on earth. Knowledge of these patterns is critical for a variety of resource management issues. In this study, month-year rainfall maps from 1920-2007 were developed for the major Hawaiian Islands. A geostatistical method comparison was performed to choose the best interpolation method. The comparison focuses on three kriging algorithms: ordinary kriging, cokriging, and kriging with an external drift. Two covariates, elevation and mean rainfall, were tested with cokriging and kriging with external drift. The combinations of methods and covariates were evaluated using cross validation statistics, where ordinary kriging produced the lowest error. To generate the final maps, the anomaly method was used to relate station data from each month with the 1978-2007 mean monthly maps. The anomalies were interpolated using ordinary kriging, and then recombined with the mean maps to produce the final maps for the major Hawaiian Islands.