Changes of extreme precipitation in the Philippines, projected from the CMIP6 multi-model ensemble

Abstract

The Philippines is highly vulnerable to the impacts of climate change including increased frequency of extreme weather events such as very heavy rainfall. Extreme rain events have resulted in landslides and floods, accompanied with a loss of life and the deterioration of infrastructure. To project the future changes of extreme precipitation in Philippines, we investigated the observations based on 53 stations and 24 CMIP6 (Coupled Model Inter-Comparison Project Phase 6) models. We applied generalized extreme value (GEV) distribution and multivariate bias-correction to series of annual maximum daily precipitation (AMP1) data acquired from the observations and models under three shared socioeconomic pathway (SSP) scenarios (SSP2-4.5, SSP3-7.0, and SSP5-8.5). We employed a model ensemble method that takes both independence and performance of model into account, which is named as the PI-weighting. To quantify the uncertainty of predicting the future AMP1, variance decomposition method was applied. Return values for 20-year and 50-year as well as the return periods of the AMP1 compared to the past (1975–2014), were estimated for two future time which are period 1 (2021–2060) and period 2 (2061–2100). From this study, we predict that the relative increases of 20-year return value of the AMP1 from the past to the year 2100 be about 8.5% in the SSP2-4.5, 11.6% in the SSP3-7.0, and 17% in the SSP5-8.5 scenarios, respectively, in the spatial median over the Philippines. We also found out that a 1-in-20 year (1-in-50 year) AMP1 observed in the past in the Philippines will likely become a 1-in-16 (1-in-37) year, a 1-in-17 (1-in-32) year, and a 1-in-14 (1-in-31) year event by 2100 under the SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios, respectively. We project that heavy rainfall will be more prominent in the northwestern and mid-western part (type I area) and the eastern coast part (type II area) of the Philippines.