Abstract:
This study analyzed recent extreme weather events in Rwanda with
emphasis on drought during March-May (MAM) season using Z-index. Composite
analysis identified the years 2009 and 2010 as the most recent dry and wet years
respectively. Analysis of the interanual variability over the period of 1981-2010
shows thatapproximately 30% and 27% of the observed rainfall events were
drought and flood cases, respectively. The mean MAM rainfall ranges from 90 to
180 mm in the wet year (2009), whereas during the dry year (2010), rainfall was
poorly distributed both in space and time.The dry year experienced generally dry
easterly winds, with almost uniformly increasing positive wind speed variation
with height.The diagnosis of the evolution of Mascarene High (MH) ridge shows
that during the dry year,the ridge is anomalously displaced to the westof its normal
position, leading to rainfall deficit over the entire eastern Africa. The dry year
exhibited a wide spread moisture divergence anomaly at low level. The noted
circulation anomalies associated with the dry event are important in future
monitoring of occurrence of drought.
