Use of the Indian ocean dipole indices as a predictor of east African rainfall anomalies

Abstract

This study was devoted to the improvement of prediction skill of east African seasonal rainfall through the use of improved knowledge of the teleconnections between Indian Ocean Dipole (laD) evolution phases and the East African rainfall variability. The specific objectives of the study included determination of teleconnections between east African seasonal rainfall extremes and space-time evolutions of the various laD phases; investigating the physical mechanisms of the teleconnections; and determination of the predictability potentials of laD indices. The data sets used in this study include rainfall data for the three East African countries (Kenya, Uganda and Tanzania), global sea surface temperatures (SSTs) and NCARINCEP reanalysis data. The study period extended from 1950 to 2003. To achieve the objectives of the study, statistical and dynamical methods were adopted in this study. The statistical methods used in the study include standardization of anomaly indices; together with correlation, regression and composite analyses. Spacetime characteristics of a series of dynamical parameters were investigated using products from ECHAM4.5 general circulation model (GCM) and the NCEPINCAR reanalysis to ascertain the physical reality of the laD-seasonal rainfall linkages derived from the statistical approaches. The results of the study demonstrated that some of the extreme rainfall conditions over Eastern African hiring' the short rainfall season were associated with positive and negative laD phases. Such information will help to improve monitoring, prediction and early warning of extreme rainfall events over east Africa, reduce the vulnerability, and improve the resilience of the society of the region to negative impacts of extreme rainfall events that are common in the region.