Intensification of the hydrological cycle expected in West Africa over the 21<sup>st</sup> century

Abstract

Abstract. This study uses the high resolution outputs of the recent CORDEX-AFRICA climate projections to investigate the future changes in different aspects of the hydrological cycle over West Africa. Over the twenty-first century, temperatures in West Africa are expected to increase at a faster rate (+ 0.5 °C per decade) than the global average (+ 0.3 °C per decade), and mean precipitation is expected to increase over the Guinea Coast (+ 0.03 mm/day per decade) but decrease over the Sahel (− 0.005 mm/day per decade). In addition, precipitation is expected to become more intense (+ 0.2 mm/day per decade) and less frequent (− 1.5 days per decade) over the entire West Africa as a results of increasing regional temperature (precipitation intensity increases on average by + 0.35 mm/day per °C and precipitation frequency decreases on average by − 2.2 days per °C). Over the Sahel, the average length of dry spells is also expected to increase with temperature (+ 4 % days per °C), which increases the likelihood for droughts with warming in this sub-region. Hence, the hydrological cycle is expected to increase throughout the twenty-first century over the entire West Africa, on average by + 11 % per °C over the Sahel as a result of increasing precipitation intensity and lengthening of dry spells, and on average by + 3 % per °C over the Guinea Coast as a result of increasing precipitation intensity only.