South Java Stream Multi-time-scale Structure

There are several temporal variabilities existing in the south Javacurrents.Because of the sparse field observation, previous studies mainlyfocused on it s seasonal character during typical monsoon season.Lessattention had been paid on the intra-seasonal variability.Based ondatasets from subsurface mooring, reanalyzed and satellite datas,maximumentropy spectral analysis is used to specify the different time-scalesof the south Java currents. It shows that the south Java currents haveintra-seasonal and semiannual variabilities.Furthermore,theintraseasonal variability of south Java currents is closely related tothe Madden-Julian Oscillation (MJO). After the equatorial trapped Kelvinwave excited by MJO arrives at the eastern boundary of Indian Ocean,asouthward bifurcation of coastal Kelvin wave is generated, whichcontinues propagate along the Sumatra and Java island.This costal Kelvinwave causes south Java currents's intra-seasonal variability.Thesemiannual variability of south Java currents is closely related to themonsoon transition. During the monsoon transition periods of April/Mayand October/November,westerly wind bursts in the equatorial IndianOcean.The westerly wind forces Wyrtki Jet and an associated semiannualeastward equatorial downwelling Kelvin wave. After this equatorial Kelvinwave arrives at the eastern boundary of Indian Ocean,a southwardbifurcation of coastal Kelvinwave is generated, which continues propagatealong the Sumatra and Java island. The semiannual variability of southJava current is mainly caused by this costal Kelvin wave.