21 - Structure of the Somali Jet deduced from aerial observations taken during June–July, 1977

Summary

An aerial reconnaissance programme was sponsored by the US National Science Foundation in June and July 1977, under which NCAR's Electra was employed in thirteen flights to reconnoitre the Somali Jet by the east African coast. The base of the operations was Nairobi, Kenya.

Cross-sections along 2° S between 37° E and 44° E disclosing the kinematic structure of the jet on four different days were constructed from observations taken on these flights. The major points of interest of these cross-sections are the mesoscale variation of the jet, both in intensity and in its frequency of occurrence, and the existence of a secondary wind maximum over the Indian Ocean near the coast. The water vapour flux across 2° S for three different days (11 June, 15 June and 5 July) and one night (29 June) was computed for the section between 1000 mb and 700 mb and 37° E and 44° E. These fluxes revealed some day-today variations. The average flux was found to be 1.79 × 10¹⁰ tonnes per day. This shows the water vapour flux for August 1964 across the Equator between 1000 mb and 450 mb and between 420° E and 75° E previously to have been underestimated.

Introduction

Findlater (1971) described the climatology of the low-level monsoon flow in the south Indian Ocean. A major feature of this flow is a jet stream along the east African coast popularly called the Somali Jet.