Spatial and Temporal Rainfall characteristics Over Seychelles

Abstract

While Seychelles lies close to the Equator, it experiences only one rainy season. The rainfall characteristics over this region is evident from the Satellite observations which show that during most part of the year the active clouds are concentrated to the eastern sector of the equatorial Indian Ocean and Seychelles comes under active weather only during southern hemisphere summer. The main objective of this study was to therefore investigate the spatial and temporal characteristics of rainfall over Seychelles during the rainy season. The specific objectives included demarcating Seychelles into rainfall homogeneous zones, identify the rainfall season, determine the onset and cessation of the rainy season. The data used in the study were the daily and monthly rainfall over Seychelles for the period 1972 to 2006 and NCEP reanalysis data. The methods used to analyze these data were Principal Component Analysis (PCA), time series analysis, pentad and cumulative curves. The results from PCA analyses showed that Seychelles may be divided into four rainfall homogeneous zones. The study also shown that the rainfall season occur between November and March. January was observed to be the peak rainfall month, while July has the lowest amount of rainfall. The onset and cessation of the rainy season occur in the month of November and March respectively. Analysis of the low level flow showed the Near Equatorial Trough (NET) is the main system influencing rainfall over the Seychelles region. During the time of maximum rainfall in January, the Inter-Tropical Convergent Zone (ITCZ) lies far to the south of the country