Rainfall Trends in Hawaii

Abstract

A recent study in Queensland, Australia, associates long-term downward trends in rain amount with the productivity of the sugarcane industry. The relationship is attributed to an increasing colloidal stability in the clouds caused by additional cloud condensation nuclei shown to be present in the smoke coming from local cane-harvesting fires. As an additional test of the hypothesis, the rainfall records of several sugar-producing areas in Hawaii are examined where burning prior to harvesting is also practiced. Two physically similar leeward coastal areas were selected for comparison, one because it is downwind from a major cane-growing region and the other because it is not. The data suggest a downward trend in rainfall over periods of 30?60 years at both areas, but the trends are not statistically significant. However, the records for areas along the windward coastal regions of the two northwesternmost islands indicate an upward trend. It is concluded that factors other than cane-fire smoke are probably involved in any rainfall trends which may exist.