Intraseasonal "monsoon jets” in the equatorial Indian Ocean

Abstract

The zonal wind in the equatorial Indian Ocean (EqIO) is westerly almost throughout the year. It has a strong semiannual cycle and drives the spring and fall Wyrtki jets. In addition, high resolution daily satellite winds show "westerly wind bursts” lasting 10-40 days, associated with atmospheric convection in the eastern EqIO. These bursts have the potential to produce intraseasonal eastward equatorial jets in the ocean. Using an ocean model driven by QuikSCAT scatterometer winds, we show that strong westerly bursts associated with summer monsoon intraseasonal oscillations can drive "monsoon jets” in the eastern EqIO, which have been observed recently. Although there are distinct equatorial wind bursts associated with Madden-Julian oscillations in January-March, they do not produce equatorial jets in the ocean. The role of ocean dynamics in producing the selective response of the ocean is discussed.