A study of Somali jet variability from Monsoon -77 and MONEX data

Abstract

Three aspects of the variability of Somali jet have been examined: (i) Quasi. periodic fluctuations over Indian Ocean maxima zone, equatorial zone near the jet axis over northeast Africa and southwest Arabian Sea maxima zone; (ii) Diurnal variation in the jet speed over land and sea; (iii) Fluctuations in the speed and level of jet over Arabian Sea.

The power spectrum analysis of the winds in the low level jet region brings out prominent and sharp spectral peaks in the period range! of 8-12 days. Oscillations in the 4-6 days range and 18-25 days range are also seen.

Diurnal variation in jet speed is seen to be prominent over the land area. It is an order of magnitude less over the sea area and has an opposite phase at g,50 and. 800 mb levels.

Modal frequency of the level of maximum wind shows variation with latitude, shifting to a lower height from south to north over Arabian Sea and the mean level of maximum wind slopes downward from south to north.