Rainfall Pattern in Freetown, Sierra Leone: from a Retrospective Viewpoint

Introduction and Purpose: It is now apparent that the changing weather patterns are associated with climate change according to the UN Intergovernmental Panel on Climate Change. In the wake of relatively little work looking at rainfall pattern in tropical countries of developing nations, especially in Sierra Leone, we conducted a retrospective analysis on the amount of rainfall over the past few decades for Freetown, the capital of Sierra Leone. Methods: Annual rainfall data from 1960-2009 were obtained from the Sierra Leone Meteorological Department (SLMD). Average monthly and total yearly rainfall data were calculated for five decades (1960-1969; 1970-1979; 1980-1989; 1990-1999; 2000-2009). Results: It was revealed that August had the highest amount of precipitation and a constant fluctuation of total annual rainfall around the mean was observed. There was no significant difference among the average total rainfall for the five decades. With a seemingly decline in average total rainfall, there are signs of increased rainfall in the last decade (2000-2009) probably due to a combination of factors, among which includes an increase in cloud condensation nuclei that are mainly derived from anthropogenic input through combustion activities. Conclusion: The study revealed marked variation in total rainfall pattern around the mean in Freetown over the past half century.