Observational aspects of the low-level cross-equatorial jet stream of the western Indian Ocean

Summary Studies of all available upper wind data up to 3 km over eastern Africa and the western Indian Ocean reveal a major low-level air current circulating at about 1.5 km in the western periphery of the monsoon regime. The current originates in the southern hemisphere and penetrates progressively further north in spring until it reaches its maximum development in July. The major current is composed of systems of low-level jet streams which can be located on a daily basis, always in the same geographical areas, with speeds reaching 25–50 ms^–1 at heights of only 1–1.5 km. Because the current is topographically-locked over eastern Africa the massive flow of air from one hemisphere to the other can be monitored and some relationships with the rainfall of parts of western India can be deduced.This paper is only a brief review of the observational and analytical studies which have been carried out and reference should be made to original papers for details of the structure and development of the current.