Interannual modulation of intraseasonal sea level variability along the southern coast of Java']Java

The intraseasonal variability (ISV) of sea level anomalies (SLAs) along the southern coast of Java and its interannual modulation were studied based on a gridded SLA product produced from the Archiving, Validation, and Interpretation of Satellite Oceanography dataset. This ISV is induced by the propagation of intraseasonal Kelvin waves derived from the central equatorial Indian Ocean (EIO). Wavelet analysis and empirical mode decomposition of intraseasonal SLAs along the southern coast of Java showed interannual variability, with weaker ISV events during El Nio years and positive Indian Ocean Dipole (IOD) years than during normal years. This interannual modulation of the ISV is influenced by the El Nio-Southern Oscillation teleconnection via the Walker Circulation and eastern Indian Ocean upwelling connected to IOD events. The anomalously weaker Walker Circulation during El Nio events generates anomalous surface easterlies over the central-eastern tropical Indian Ocean that produce upwelling Kelvin waves in the EIO and offshore water transport along the southern coasts of Sumatra and Java, resulting in negative SLAs along the southern coast of Java. These negative SLAs damp the positive SLAs induced by the eastward propagation of downwelling Kelvin waves from the central EIO during the following March-May of El Nio years. Similar features of SLAs and sea surface wind anomalies also occur during positive IOD years. Consequently, the sea level ISV along the southern coast of Java is weaker in El Nio and positive IOD years.