Geographical Patterning of Interannual Rainfall Variability in the Tropics and Near Tropics: An L-Moments Approach

Abstract Interannual rainfall variability has important effects for the evolution of biotic and human communities. Historical records of monthly rainfall totals for 1492 stations within 30° of the equator were analyzed using the method of L-moments. The 0.1 quantile (QU10), or the proportion of mean annual rainfall expected in the driest year in 10, was selected as the measure of variability. A nonlinear regression was fit to the relationship between QU10 and mean annual rainfall, and regions were categorized into three classes on the basis of the residuals: the 25% with the most negative, the 25% with the most positive, and the middle 50%. Maps of the global and regional patterns of rainfall variability show marked geographical patterning of variability and identify areas where rainfall variability may be a particularly important environmental feature.