The Turkana low-level jet: mean climatology and association with regional aridity

This article develops the first climatology of the low-level jet that prevails in the Turkana Channel of northern Kenya. ERA-Interim data are utilized, giving the analysis a resolution of 0.75 degrees of latitude/longitude and a temporal resolution of 6 h. The jet is found to be a semi-permanent feature, its occurrence ranging from 69% of the days in May to 90% of the days in October. It is strongest during the June-September dry season. Typical core speeds in a 0.75 x 0.75 grid point are 10-15 m s(-1). The Turkana Jet is clearly a nocturnal feature, being strongest at 0000 UTC or 0600 UTC and usually barely discernible at 1200 UTC. There are distinct patterns of divergence and vertical motion associated with the jet and these differ between the entrance, core, and exit regions. The jet appears to modulate rainfall, especially during the nocturnal hours, with strong jets suppressing rainfall. It also appears to be a factor in the prevailing aridity in the northeast Kenya, southern Somalia, and southeastern Ethiopia and the absence of a summer rainy season in this region.