Memahami SST di wilayah Indonesia (part 2)

In the ensuing study, the ocean has a function to stabilise the surface temperature of the Earth due to its ability to organise latent heat and to perform as the dominant source of atmospheric moisture and the spatial distribution of the moisture flux to the atmosphere are controlled by SST as was explained in many text books (e.g. Duxbury et al., 2002; Tomczak and Godfrey 2003). To take an example, in previous work, Nicholls (1981, 1984) shows that air-sea interaction in Indonesia is related to SST anomalies and it has a strong seasonal relation with Pacific Ocean. The above description gives a clear argument that SST is the principal oceanic parameter for the atmosphere. Next question arises, how does the mechanism generating the SST?

The mechanisms that generate and maintain SST within Indonesian seas are consequence of the complex topography and connectivity between the Pacific and the Indian Oceans (Qu et al., 2005). The SSTs across the Indonesian region are importance to convection and precipitation distribution. This sensitivity relationship has been investigated either by models (Miller et al., 1992) or by observations (McBride et al., 2003).To figure it out, Qu et al. (2005) used modeling experiment in order to see the sensitivity of the atmosphere to underlying SST. They found that warm SSTs around the region lead to extensive amounts of evaporation and drive deep convective cell activity over the region. This means that the SST in this region is very sensitive to the atmosphere (Figure 1).

Even though the SST variability in the region is small compared to the tropical eastern Pacific because of less of strong equatorial upwelling, the mean SST in this region is relatively high (Qu et al., 2005). For example, the eastern part is the largest in SST variation as we can find it in the Banda Sea, Timor Sea and Arafura Sea, where the amplitude exceeds 4^o C (Susanto and Gordon, 2005; Qu et al., 2005; Setiawan, 2008). These parts are strongly influenced by the western Pacific warm water pool, since geographically they are close to the channel. Moreover, the other reports showed that the SST in these parts also can be influenced by remote equatorial winds in the Pacific and Indian Oceans. This mechanism allows the El-Nino-Southern Oscillation (ENSO) to influence regional SST (Potemra, 2001). In addition, the occurrence of the SST cooling also found in the Makassar Strait during the peak of 1997/1998 El-Nino period (Susanto and Gordon, 2005).