Assessment of the seasonal fluctuations in relative isotopic abundances of oxygen-18 and deuterium in rain water from the Tucson Basin, Arizona

Abstract

Rainfall in the Tucson Basin, located in southeastern Arizona, averages about 30 centimeters annually and is distributed unevenly between the summer and winter rainy seasons. Additionally, both the source of water vapor and the meteorological conditions differ during summer and winter storms. Previous investigations in the Tucson Basin and elsewhere have noted seasonal variations in the relative isotopic abundance ratios of oxygen-18 and deuterium and have attributed this variation in part to the meteorological conditions that prevailed during each storm. The purpose of this study was to use simple statistical tools to evaluate variations in isotopic abundance ratios in terms of ground level meteorological conditions, specifically, rainfall amount, air temperature, cloud ceiling elevation, rainfall intensity, and relative humidity. When evaluated individually, the amount of storm precipitation had the largest effect on summer and winter storm sets, whereas, temperature had the greatest effect when compared with the combined or yearly storm set.