Semiannual Kelvin Waves Propagation along the South Coast of Sumatra-Jawa-Bali and the Lesser Sunda Islands Observed by TOPEX/POSEIDON and ERS-1/2 Satellites

Abstract

The merged TOPEX/POSEIDON (T/P) and ERS-1/2 altimeter data during 10/14/1993 - 2/12/2002 have been used to study Indian Ocean Kelvin waves propagation along the south coast of Jawa, Bali, Lombok, and the Lesser Sunda Islands. The results show that the occurrence of semiannual Indian Ocean Kelvin waves either in April/May or November/December for all the year of 1993-2001 (except in 1994) with the intraseasonal period and phase speed ranging from 35 to 90-day and 1.54 to 2.9 m/s, respectively. 1 Background Equatorial Kelvin waves, coming from the western equatorial Indian Ocean, impinge on the west coast of Sumatra on the equator and stimulate a reflected Rossby wave back into the Indian Ocean, and northward and southward propagating, coastally trapped Kelvin waves (CTKW's) (Clarke and Liu, 1993;1994). Sprintall et. al. (1999) employed a simple analytical model to predict changes in coastal sea level due to along-shore wind stress by decomposing the momentum equations into vertical modes, and integrating along the path taken by Kelvin wave. They resolved the timing of the event of the incoming Indian Ocean Kelvin wave predicted in the current meter mooring at Cilacap (South Jawa water) match well with the observation. Figure 1 shows volume transport versus time at the current meter moorings MAK 1 and MAK 2 at the narrowest Labani channel within the Makassar Strait. An interesting event happened when the transport varied from 0 Sv. during the late of May 1997 to over 20 Sv in July 1997. Sprintall et. al. (2000) showed that this event was associated with an Indian Ocean coastally trapped Kelvin wave passing through Lombok Strait before entering Makassar Strait. The Kelvin wave was due to westerly wind forcing in the remote equatorial Indian Ocean during the semi-annual April/May monsoon transition period (Wyrtki,