and is distributed in a bimodal pattern from late April until November. In the forest-savanna mosaic (FSM) zone rainfall is mostly bimodal with an average precipitation of 1300–1800 mm and a crop-growing period of 240–330 days. The rainforest (RF) zone has a bimodal or unimodal rainfall pattern with a short or no dry season with 1500–3000 or 4000 mm per year. The growing period ranges from 270 days to all year round. The relative humidity fluctuates seasonally between a mean minimum of 60% during the dry season (January) to a mean maximum of 80% during the rainy season (July) near the coast, declining steadily from the coast towards the north of the countries. The SS, NGS, SGS, FSM zone and RF were designated as 1–5 in the correlation analysis, following the order of increasing precipitation. Three sites in the coastal savanna of Ghana were analyzed as part of the SS because of their similar climate.