Evaluation of TRMM-based Standardized Precipitation Index for drought monitoring in the Philippines
Drought is a recurrent phenomenon of a climate system and is primarily caused by below normal precipitation. This study evaluated the potential of satellite-based Standardized Precipitation Index (SPI) derived during the period of 1999 to 2018 from Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA 3B43 v7) for drought monitoring in the Philippines as a substitute for the recommended synoptic-based index. The TRMM-based SPI estimates were compared with synoptic-based SPI at different timescales (SPI-1, SPI-3, and SPI-6) from 45 synoptic stations with 30 years of precipitation data. Although computation of SPI generally requires at least 30 years of precipitation data, results showed that SPI derived from TRMM agreed with synoptic-based SPI estimates. The correlation coefficient, r, increases as the timescale in SPI derivation gets longer (SPI-1 with r=0.817 to SPI-6 with r=0.850), while root mean square error decreases. This study demonstrated the potential of TRMM-based SPI to monitor drought in the Philippines.