The spatial correlation structure of rainfall at the local scale over southern Ghana

Study region: Ghana is located in west Africa by the coast with the majority of the annual rainfall coming from the west African monsoon. Study focus: Thanks to a new dense, long-term dataset the spatial structure of rainfall for the different phases of the monsoon has been investigated. Previous studies have only considered a general decorrelation range whereas in this study a novel approach of estimating the decorrelation rate depending on the intensity of the rainfall event has been implemented. The anisotropic pattern at the subweekly and local scale was also modelled. New hydrological insights for the region: The spatial correlation structure of rainfall varies greatly with the intensity of the rainfall event and the phase of the monsoon, with a much shorter range for low intensity rainfall compared to other intensities. At the very local scale (∼10 km), there is a much larger variation over the year at the lower intensities compared to the heavier, indicating a larger variation in the structure of the convective systems generating low amount rainfall compared to heavy rainfall systems. The westward propagation of convective systems can be seen even at short aggregation periods and local scale.