El Niño Southern Oscillation (ENSO) and its Effect on Rwanda Climate.

Abstract

The sea surface temperature (SST) in the tropical pacific region known as Niño1, 2, 3, 3.4 and 4 regions are always analysed to identify the El Niño-Southern Oscillation (ENSO) episode. As SST in that region exceed the normal SST (warm period) at that time the El Niño (EN) event is on, and contrary when it is lower than the normal SST it is the La Niña (LN) event. The two events have a global atmospheric pressure oscillation named ENSO. In this study we look on overview of this phenomenon during a period of 34 years (1983-2017) and the target is to analyse generally this phenomenon mainly some of the strong events, to generalise the health effect related, and in particular to identify its effect on Rwanda climatology by analysing the annual mean trends of rainfall, maximum and minimum temperature. The objectives of this research was reached and expanded. The annual mean rainfall, maximum and minimum temperature for the non ENSO years are 2.83mm, 25.66oC and 14.33oC respectively while every station’s data is mentioned in this study. We focus on the strong ENSO event and even the recent EN (2019-2020) for its general situation, the study has shown that EN event cause the annual mean maximum and minimum temperature across the Rwanda to increase except EN of 1997-1998 and LN cause the decrease of both annual mean maximum and minimum temperature except LN of 1998-1999. For annual mean rainfall, this study has shown that ENSO episode itself does not explain the variability of rainfall over Rwanda but there are other rainfall drivers mentioned in this study to be considered for a full reason of the rainfall variability including ITCZ, topography, subtropical anticyclones etc.