The self-organizing map (SOM) was performed to detect how many types of sea surface temperature (SST) anomaly patterns can be distinguished in the distribution of SST anomalies in the South Indian Ocean during austral autumn for 1901-2010. 12 clusters of SST anomaly patterns were identified. Two of them are characterized by a dipole pattern with opposite SST anomalies in the Southwest Indian Ocean and its northeast side, which is similar to the so-called Indian Ocean Subtropical Dipole (IOSD), and they are named as traditional IOSD (T-IOSD) in the present work. Two other clusters also show a dipole pattern of SST anomalies, but with weaker amplitudes and more eastward location, called the new IOSD (N-IOSD) here. There are significant differences in the evolution of T-IOSD and N-IOSD. For positive phase of T-IOSD, the warm (cool) SST anomalies are first developed to the south (northeast) of Madagascar in previous spring, then migrate eastward and form the typical pattern of IOSD in summertime, and maintain to autumn. On the contrast, significant SST anomalies of N-IOSD event are first observed to the west of Australia in early summer, develop into a well-organized dipole pattern in late summer, which is approximately two or three months later than the mature phase of T-IOSD. Investigation of the mechanism responsible for developing of both T-IOSD and N-IOSD events shows that latent heat flux plays an important role in the growth of SST anomalies. Shortwave radiation and oceanic dynamic processes also contribute to the T-IOSD formation. The meridional advection by anomalous oceanic current is another key process in the N-IOSD development.