Relationship between rainfall, altitude and distance from the sea in the Freetown Peninsula, Sierra Leone

Statistical analysis of mean monthly rainfall measured by 31 gauges in the Freetown Peninsula shows clear differences between those facing the south-westerly monsoon and those in the peninsular rain-shadow. Whilst catches between ocean-facing and rain-shadow gauges were very similar in the drier months of December to May, catches by ocean-facing gauges were considerably greater in the wetter months of June to October, and their catches varied less spatially. Rainfall in the monsoon months increased with altitude, but the relationships between monthly rainfall and altitude were more marked for rain-shadow gauges than for ocean-facing gauges. Rainfall in the monsoon months also tended to decrease with distance from the sea, and whilst the decreases were similar in magnitude for both rain-shadow and ocean-facing gauges, the decreases per km distance were less variable in the rain-shadow than where gauges faced the ocean. Two gauges, one in rain-shadow and one ocean-facing, were found to catch less than expected; and two gauges in the ocean-facing group were found to be particularly influential in determining the regression fit.