Solar forcing of Socotra's Holocene climate

The arid tropical island of Socotra is located in the northwestern part of the Indian Ocean, between the horn of Africa and the Arabic peninsula. Rainfall has a strong bimodal distribution on Socotra, associated with the migration of the Intertropical Convergence Zone (ITCZ). Precipitation is delivered as the northward migrating ITCZ passes over the island in May-June and returns during its southward migration from September to December. Little or no rain falls on Socotra during the summer (southwestern) and winter (northeastern) monsoons (Shakun et al., 2007). The 1540m-high SW/NE oriented Haggeher Mountains create a watershed on the island forcing precipitation derived from the ITCZ passages, to fall mainly on the windward side of the mountain range. As a consequence the precipitation associated with the northward migrating ITCZ falls mainly on southwestern part of the island whereas precipitation related to the autumn passage of the ITCZ falls mainly on the northeastern part of the island (Scholte and De Geest, 2010).