Diagnosis of meteorological factors associated with recent extreme rainfall events over Burundi

Abstract

This study aims to identify the main causes of extreme rainfall events specifically recent ones that occurred in Central East Africa, which seriously affected the western part of Burundi causing 77 deaths, destruction of infrastructures, loss of properties and hectares of lands in February, 2014. To understand underlying issues about extreme rainfall occurrence and its key drivers, the present study investigated two distinct extreme rainfall events that caused massive losses in the western part of Burundi on November 11th, 2009 and February 9th, 2014. Different datasets have been used to depict which one captured reliable information of the two extreme rainfall events investigated. Analysis of different weather parameters was conducted using the European Centre for Medium-Range Weather Forecast (ECMWF) datasets. The Weather Research and Forecasting (WRF) Model was also employed to analyse different parameters over different periods, thus prior, during, and after the occurrence of an extreme rainfall event. It was found that the two distinct rainfall events were induced by the combination of local convection enhanced by moist air from the Congo basin and abnormal conditions in the mid-upper layer. Instabilities in the lower and mid-upper layers mainly emanated from the changes in geopotential height and wind circulation. Local physical factors especially the topography and the presence of the Lake Tanganyika localized in the Western Rift Valley of Africa enhanced local convection which triggered rapid condensation that induced a heavy rainfall over the western part of Burundi. Weather conditions vary depending on the time or season of occurrence of the extreme rainfall events. This study will propel future studies on historical diagnosis and forecasting of extreme weather events over Burundi. It will also guide policy-makers to mitigate negative impacts expected from future occurrences of extreme weather events.