Abstract
A quantitative assessment of drought characteristics and their associated variability in the Northern Nigeria was carried out. Monthly rainfall data for all the selected locations which span a period of 100 years (1907-2006) collected from the Climate Research Unit (CRU) database were used. The resolution of the data is 0.5 × 0.5 degrees in longitude and latitude. The long-term rainfall records were analyzed for drought using standardized precipitation index (SPI). The 100 years of Study was subdivided into 10 decades. Using Ilwis GIS software, the SPI results were presented on a spatial digitized map of northern Nigeria. This was done using the coordinates got from the Nigerian Meteorological Agency, Lagos Nigeria. The results of SPI analysis revealed that there were several drought years in the study period. Analysis further revealed that decade 7 to decade 9 (i.e. 1967-1976, 1977-1986, 1987-1996) witnessed persistent drought in the northern Nigeria. These were classified into mild, moderate, severe and extreme drought conditions. Near normal dry or mild drought was predominant in the 100 years of study. Mild drought has the highest number of occurrence in the northern Nigeria. A closer examination shows that north eastern part of Nigeria is susceptible to moderate drought. SPI analysis for 1, 3, 6 and 12 months was carried out. According to the Nigerian Meteorological Agency Classification, 1 month represents meteorological drought, 3 months represents agricultural drought, 6 months represents hydrological drought and 12 months represents socio-economic drought. The SPI analysis revealed distinct period of negative and positive values in which negative values indicate occurrence of drought and positive values imply there is no drought. This study has provided useful information and pro-active intervention to reduce the impact of drought which will be helpful to effectively plan rain-fed agriculture in northern Nigeria.
Highlights
Drought is a period of unusually dry weather within a geographic area where rainfall is normally present, during a drought spell there is lack of precipitation
Drought occurs in both high and low rainfall areas and virtually all climatic regions, in the past, drought was only associated with arid, semi-arid and desert fringes when definition was based only on absolute rainfall amounts with drought spells being associated with onset and cessation dates of rains and length of the rainy season, it is better defined as ineffectiveness of precipitation
Analyses further revealed that the decade 7-decade 9 witnessed the persistent drought in the major parts of the northern Nigeria
Summary
Drought is a period of unusually dry weather within a geographic area where rainfall is normally present, during a drought spell there is lack of precipitation. In the southern parts of Nigeria, the current occurrence of armed robbery was believed to be related to the insurgence of migration from Sahel to the coastal areas of Lagos and Niger Delta in the early seventies [1] Drought occurs in both high and low rainfall areas and virtually all climatic regions, in the past, drought was only associated with arid, semi-arid and desert fringes when definition was based only on absolute rainfall amounts with drought spells being associated with onset and cessation dates of rains and length of the rainy season, it is better defined as ineffectiveness of precipitation. The persistence of drought in parts of northern Nigeria during 1970s, 1980s and 1990s has been attributed to the prevalence of a stagnated anti-cyclonic circulation of the tropical atmosphere over areas that normally should be exposed to rising arm of tropical Hadley Cell Circulation by mid-summer [3] [14] [15] These conditions are themselves related to the tropical component of global general circulation system
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