2

• Main Authors: Okoro U. K, Chen W, Chineke T. C, Nwofor O. K
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Niger Delta; monsoon; rainfall anomaly; variability; index; trend; South Atlantic Ocean
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.678.4438; http://www.ijset.net/journal/291.pdf

Abstract: This study presents the inter-annual variability of rainfall over 6 locations spread across the Niger Delta region of Nigeria (4.15°N- 7.17°N, 5.05°E- 8.68°E) from 1981 to 2004. The monthly rainfall variability from rain gauge only datasets of the Nigerian Meteorological Agency (NIMET), rain gauge interpolated datasets of the Climatic Research Unit (CRU) Time Series (TS) version 3.20 and the interpolated datasets from rain gauge, model and satellite estimates of the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) were analyzed. Also the relationship between the Ocean Nino Index (ONI) and the South Atlantic Ocean Dipole Index (SAODI) which are rainfall driving mechanisms and the rainfall variability over the region has been investigated. The objectives are to present the rainfall variability patterns across the locations within the region as well their annual- and wet season- interannual rainfall variability indexes, and to investigate the links between the ONI and the SAODI and the monthly rainfall variability over the region. The results show increases in the trends of rainfall variability patterns over the region both at the various locations and on the areal average of rainfall whereas it has been noted that the rainfall variability on small areas can be over- or under- estimated when considering large areal averages. However the interannual variability of the monthly rainfall anomaly over the region is not strongly linked to both the ONI and the SAODI, which is an indication that the mechanism(s) driving rainfall variability over the region is yet to be understood.