Climatic variations in tropical West African rainfall and the implications for military planners
Montgomery, Christi S.
McMaster, Michael T.
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We have identified statistical and dynamical relationships between summer rainfall variations in tropical West Africa (TWA) and El NinÌ o/La NinÌ a (ENLN) events in the tropical Pacific. Our primary data sets were the National Centers for Environmental Prediction / National Center for Atmospheric Research reanalysis fields and the Multivariate ENSO Index (MEI) for the period 1970- 2007. Correlations of TWA rainfall and MEI time series showed that high (low) TWA rainfall was significantly correlated with LN (EN) events, with LN (EN) leading by zero to seven months. Composite analyses showed that ENLN impacts on TWA occurred via global scale equatorial Rossby-Kelvin waves and Southern Hemisphere Rossby wave trains that extended into the tropical African region. We also found regional connections between positive (negative) sea surface temperature (SST) anomalies in the Gulf of Guinea and Angola coastal waters and negative (positive) TWA rainfall anomalies. We expect our results to contribute to improved long lead rainfall predictions for TWA. This would allow military and civilian planners to construct a more effective framework for Theater Security Cooperation in TWA, including strategies for mitigating the impacts of climate variations and climate change.
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