A major low‐level air current near the Indian Ocean during the northern summer

Abstract

It is demonstrated that high‐energy flow, in the form of low‐level southerly jet streams which have been reported earlier over Kenya, is only one part of a much more extensive current of air which flows rapidly around the western half of the Indian Ocean during the northern summer. The high speeds are associated with the concentration of the cross‐equatorial airflow into the zone from longitude 38 deg E to about 55 deg E instead of being rather evenly distributed from 40 deg to 60 deg or 80 deg E as illustrated in many climatological atlases and charts of mean flow during the season. The high‐speed current is shown to flow intermittently from the vicinity of Mauritius through Madagascar, Kenya, eastern Ethiopia, Somalia and thence across the Indian Ocean to the west coast of India and beyond. The stream is occasionally reinforced by northward flow through the Mozambique Channel. The high‐speed air current, or system of low‐level jet streams, is closely associated with the Intertropical Convergence Zone over the Arabian Sea and western India, and variations in the strength of the stream over Kenya during a two month period were related to the rainfall which western India received from the south‐west monsoon.