On meteorological droughts in tropical Pacific Islands: time‐series analysis of observed rainfall using Fiji as a case study

Abstract

AbstractAnalysis of historical droughts was undertaken by converting observed monthly rainfall over the period 1949–2008 to the Standardized Precipitation Index (SPI). The modified Mann–Kendall test applied on monthly rainfall showed statistically significant downward trends at significance level α = 0.01. The Sen's Slope, estimated from the time‐series, revealed statistically significant decreases in annual rainfall ranging from ∼13 to 47 mm year−1. Based on the SPI, drought duration and severity was non‐uniform across stations over the 60 year period. The strongest impacted stations were located in western and northern Fiji where rainfall deficiency for the period 1969–1988 led to a dramatic increase in moderate and severe droughts. The return periods of annual rainfall were much longer at these stations relative to those in outer‐lying islands. While rainfall increased over the period 1989–2008, the actual amounts did not exceed 1949–1968 totals, confirming a net shift towards drier conditions since the 1950s. This study has demonstrated that SPI can be a useful tool for diagnosis and monitoring meteorological droughts in tropical Pacific islands. Copyright © 2010 Royal Meteorological Society