Recurrent drought and decrease agricultural productivity during the last decades in West Africa, especially in the Sahelian zone, points to the need for a clearer understanding of the Onset dates, Cessation dates, Length of growing season, dry spell lengths and their consistencies, which pose major threats to the agricultural sector.
Daily rainfall data for ten (10) years were analyzed for eight (8) meteorological stations in the Sudan Savanna region of Nigeria, with the application of INSTAT software package obtained from the UK Met office. The onset dates were gotten based on the four (4) onset definitions as defined by the package. Onset dates was also determined based on Omotoshoâ€™s definition (2000). The deviations of the four (4) onset definitions from Omotoshoâ€™s definition were gotten, so as to know the reliability of these definitions.
The cessation of rain was also determined using the water balance sheet. The first day when the water balance sheet drops to zero, after first of October was taken as the cessation. The length of the growing season was also determined, this shows a decrease northward. Also obtained was the overall chance of rain based on the Markov chain (fitted) model. Result shows two peaks for some stations, and just a single for some.
Also determined, was the probability of having a 7 and 11 days dry spell following 30 days after planting. This shows that the risk of having 11 days dry spell is very low after 30 days from planting. The risk for 7 days spell also decreased, but not as rapid as that of 11 days.
TABLE OF CONTENTS
1.1 Aims and Objectives
2.0 Literature Review
3.0 Study Area
3.1 Data and Methodology
4.0 Result and Discussion
4.1.1 Onset of Rain
4.1.2 Cessation of Rain
4.1.3 Length of Growing Season
4.1.4 Overall Chance of Rain (Markov Chain Fitted Model)
4.1.5 Dry Spells and their Consistencies
5.0 Conclusion and Recommendation
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