Components of rainy seasons’ variability in Equatorial East Africa: onset, cessation, rainfall frequency and intensity
Date
2009Author
Camberlin, Pierre
Moron, Vincent
Okoola, Raphael
Philippon, Nathalie
Gitau, Wilson
Type
ArticleLanguage
enMetadata
Show full item recordAbstract
The inter-annual and spatia lvariability of different
rainfall variables is analysed over Equatorial East Africa
(Kenya and northeastern Tanzania). At the station level,
three variables are considered: the total precipitation amount
(P), the number of rain days (NRD) and the daily rainfall
intensity (INT). Using a network of 34 stations, inter-station
correlations (1958–1987) are computed for each of these
variables. The spatial coherence of monthly or seasonalP
and NRD is always much higher than that of rainfall
intensity. However, large variations in spatial coherence are
found in the course of the seasonal cycle. Coherence is
highest at the peak of the short rains (October–December)
and low during the long rains (March–May), except at its
beginning. The inter-annual variability of the onset and
cessation of the rains is next considered, at the regional
scale, and the study extended to 2001. In the long rains, the
onset and cessation dates are independent of NRD and INT
during the rainy season. Hence, the long rains seasonal
rainfall total depends on a combination of virtually unrelated
factors,whichmayaccountforthedifficultyinitsprediction.
However, the onset, which exhibits a large inter-annual
variability and a strong spatial coherence, has a prime role.
Conversely, inthe shortrains,thoughthe onsetisagain more
decisive than the cessation, the different intra-seasonal
descriptors of the rains are more strongly inter-related.
Citation
Theor Appl Climatol (2009) 98:237–249Publisher
Springer Meteorology