Interstation Correlations and Nonstationarity of Burkina Faso Rainfall

Abstract

A study is presented of the rainfall regime for central and northern Burkina Faso over 1923?83. Interstation coorrelations for seasonal rainfall totals are rather low, with median 0.31. Sums of truncated daily rainfall values, with the number of rainy days as an extreme case, exhibit quite larger interstation correlations. An explanation is that factors determining the occurrence of rainfall in West Africa operate on a larger scale than those determining exact rainfall amounts. A new method is proposed for constructing regional rainfall indices from data for several locations in the presence of missing data. This method is applied in a study of (non-)stationarity of Burkina Faso rainfall. A highly significant departure of stationarity is found, which is especially expressed in earlier dates for the end of the rains, and smaller average rainfall amounts per day between the start and the end of the rains.