An analysis of daily rainfall for the cropping season in Sierra Leone

Abstract

This study is concerned with an analysis of daily rainfall in Sierra Leone, West Africa. The general aim is to characterise water-related aspects of the agricultural environment, and to provide a basis for an objective assessment of the risks and potentials for rainfed agriculture in different parts of the country. Prior to the main analysis, a detailed assessment of the rainfall data base was undertaken, which established the suitability (in terms of amount and quality) of the available records for the proposed study. An evaluation of the adequacy of the rain-gauge network in providing a realistic estimate of the spatial and temporal characteristics of rainfall was also undertaken. About 65% of the total area was found to be sampled, leaving some areas, especially the Eastern Highlands in the north and east, poorly represented by the rain-gauge network. The central concept for all analyses is the "rainday" and its complement the "dryday". Based on a definition that incorporates both the occurrence/non-occurrence of rainfall and estimated soil moisture, three types of drydays, and four types of raindays were identified. The seasonal distribution aid variability of raindays and drydays were analysed for eight stations representing eight rainfall regions.