Spatiotemporal Evaluation of Historical Drought in the Philippines

摘要

Negative impacts of drought on agriculture and water resources vary according to different timescales and intensity. In this paper, the historical droughts in the Philippines were examined using the Standardized Precipitation Index (SPI) at different timescales (SPI-1, SPI-3, and SPI-12). SPI is derived from the monthly rainfall data of Tropical Rainfall Measuring Mission (TRMM) 3B43 v7 from 1998 to 2018. A total of 384 TRMM grids in the Philippines were used in the time series analysis to investigate the spatiotemporal dynamics of drought. Results showed that the Philippines was frequently hit by different types of drought. It also showed that the spatial distribution of the past drought events varied through timescales. Particularly, more variation was observed in the entire land area using the shorter SPI timescales, i.e. SPI-1 and SPI-3. With longer timescales, values tend to be more similar and closer to each other resulting in smoother trends. The affected areas in terms of percentage were also examined. Each drought event's severity, duration, and intensity for the areal average of the Philippines was also investigated. These results demonstrate the viability of satellite-derived SPI for drought evaluation at a national level, which is important in the decision-making for drought mitigation in the Philippines.