Multivariate Extension of the Singular Spectrum Analysis A New Tool in Understanding the Intraseasonal-Oscillation (ISO) of Philippines Summer Monsoon and its Association with Extreme Rainfall Events

The intraseasonal low-frequency oscillation is studied by using gridded rainfall dataset from 1979 to present. Multivariate Singular Spectrum Analysis (SSA) was used in the extraction of these modes. We have found out that there is a significant increasing trend in the relative strength of low frequency ISO. However, this happened only after the years 1979 to 1984 was removed in the trend analysis. A previous study found that the increased rainfall during the break and transition phase of low-frequency ISO could be a contributing factor to the decreasing trend during the active phase. In this study, the implication is rather the opposite - the increasing trend in rainfall, in terms of extreme events occurrence during the active phase of low-frequency ISO had been the contributor to the increasing trend of low-frequency ISO.