Abstract
Study regionGhana is located in west Africa by the coast with the majority of the annual rainfall coming from the west African monsoon. Study focusThanks 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 regionThe 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.
Highlights
Rainfall over west Africa has received a lot of interest the past decades due to the limited possibility of irrigation for the many farmers depending on rain fed crops
The majority of the west African rainfall comes from the west African monsoon which is controlled by the movement of the inter
We have provided some insights on the spatial behaviour of daily rainfall within Ghana
Summary
Rainfall over west Africa has received a lot of interest the past decades due to the limited possibility of irrigation for the many farmers depending on rain fed crops. In contrast to the other two papers, Moron et al (2007) calculated the decorrelation distance between measured rainfall at stations instead of satellite grid points This was calculated for five different tropical regions, to assess the generality of the results, on amount and occurrence data separately by estimating the Pearson's correlation for amount data and phi correlation for occurrence. In both Greatrex et al (2014) and Teo and Grimes (2007), climatology variograms are calculated on rain gauge data to estimate the range of rainfall over Ethiopia and Gambia Both of these papers split the analysis for occurrence and positive rainfall amounts, similar to Moron et al (2007).
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