Karakteristik Gelombang Kelvin Ekuatorial Atmosferik pada Kondisi Normal (1990), La Nina (1988–1989), dan El Nino (1997–1998)
The purpose of this research is to analyze the characteristics of atmospheric equatorial Kelvin waves using spectral technique of upper winds in the level of 100 mb (tropopause) and 50 mb (lower-stratosphere) in Normal (1990), La Nina (1988–1989) and El Nino (1997–1998) condition. In tropopause, Kelvin waves are predominantly excited by deep tropical convections. Generally, behavior of Kelvin waves in the Normal condition is similar to those observed during the La Nina condition, namely the energy of waves is substantially strong over the maritime continent (Indonesia), but during the La Nina condition the energy of waves is also strong over Pasific ocean. Whereas the energy of waves over Indonesia is low during the El Nino condition because strong energy of the waves moves to western Pasific ocean following deep tropical convections. Kelvin waves have an upward energy propagation. The observed energy of the waves over Indonesia in the level of 100 mb is strong, thus, Indonesian region becomes a favorable region to induce the equatorial stratosphere circulation, especially on the quasi-biennial oscillation (QBO). In the lower-stratospher, we indetify the QBO during the period of 24 and 28 months. In the level of 50 mb the energy of Kelvin waves is strong when phase of QBO changes from easterly to westerly and westerly momentum increases. This is caused by easterly QBO phase dominates layer under the level of 50 mb, so the energy of Kelvin waves can penetrate to the level of 50 mb. The energy of Kelvin waves in tropopause is stronger than in lower-stratosphere due to distance from the forcing (tropical convection centre).