Long-term Trends in West African Rainfall Components

In the tropics, where rainfall is the dominant and most variable climate element, a complete picture of changes in tropical rainfall is rather sparse, if not absent, from the tropical climatological literature, because of the disproportional and narrow focus on rainfall totals and extremes. However, tropical rainfall can be disaggregated into a whole range of different 'components' (e.g. rainfall amount, rainfall frequency, rainfall intensity, rainfall timing, rainfall seasonality, and rainfall belts), in addition to totals, all of which may be impacted as a manifestation of global-scale climatic change. There is some evidence in the literature that rainfall totals are often less sensitive to climate variability relative to other rainfall components, and any two rainfall components may show incongruous (or divergent) trends for the same location and time span. It is therefore likely that other rainfall components are more sensitive to climate variability and change than rainfall totals, or at least differ in their respective sensitivities to climate variability and change. Using West Africa as a proxy for the tropics, this study investigates the relative changes in the full range of tropical rainfall components over the past several decades in response to the increases in global greenhouse forcings. The overarching aim of this study is to provide a holistic picture of past changes in tropical rainfall as a necessary first step in dealing with future challenges arising from changes in rainfall through climate variability and change.