Setting Africa’s rainfall straight: A warping approach to position and timing errors in rainfall estimates

There is an increasing number of rainfall products available over Africa and globally. Rainfall has considerable socio-economic impacts in sub-Saharan Africa, and the sparse gauge and radar networks make such estimates particularly valuable. They are used in many important applications such as drought/flood forecasting, water management or climate monitoring. The choice of which one to use has a significant influence on the output and performance of such applications. The large number of available rainfall products makes it difficult to select the “best” one for one’s need. Among the rainfall products, there is an increasing number of satellite-based estimates with ever finer resolution. They are particularly valuable in Africa where the gauge network is not dense enough to represent the high variability of the rainfall during the monsoon season. However, there are substantial differences between them. Rainfall events are moving systems which can be described by their positions and timings beside of their intensity. A position or timing error will also lead to mismatches in the rainfall occurrence or intensity. This is especially true for localized rainfall events such as the convective rainstorms occurring during the rainy season in sub-Saharan Africa. However, rainfall is mainly evaluated with respect to its intensity or occurrence, while position and timing errors are rarely studied.