| dc.description.abstract | The aim of this study was to derive components of the intraseasonal rainfall variations from the daily rainfall
in the Equatorial Eastern Africa region and assess their spatial coherence, a pointer to their potential predictability. Daily
rainfall observations from 36 stations distributed over Equatorial Eastern Africa and extending from 1962 to 2000 were
used. The March to May and October to December periods commonly referred to as the long and short rainfall seasons
respectively were considered.
Seasonal and intraseasonal statistics at the local (station) level were first defined. The stations were also grouped into
near-homogeneous (sub-regional) zones based on daily rainfall. Similarly, seasonal and intraseasonal statistics were then
derived at sub-regional level using three different approaches. Inter-station correlation coefficients of the intraseasonal
statistics at local levels were finally computed and plotted as box-plots.
For the two rainfall seasons, the two statistics showing the highest spatial coherence were the seasonal rainfall totals
and the number of the wet days at sub-regional level. The local variance explained for these two variables, as an average
over all the sub-regions, was more than 40%. At the bottom of the hierarchy were the mean rainfall intensity and frequency
of dry spells of 5 days or more which showed the least coherence, with the local variance explained being less than 10% in
each season. For each of the intraseasonal components of daily rainfall considered, the short rainfall season statistics were
more coherent compared to the long rainfall season. Lag-correlations with key indices depicting sea-surface temperatures in
the Pacific and Indian Oceans showed that the hierarchy between the rainfall statistics in the strength of the teleconnections
reflected that of spatial coherence. Copyright© 2012 Royal Meteorological Society | en |
