Homogenization of Daily Rainfall, Minimum and Maximum Temperature in the Philippines

Abstract

Daily rainfall, minimum, and maximum temperatures from 60 Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) synoptic stations from 1951-2022 were homogenized using the Climatol Package in which time series breakpoints were found in three stations for rainfall, 48 for maximum temperature, and 53 for minimum temperature, respectively. The identified breakpoints were validated using the station metadata gathered from a series of PAGASA workshop-dialogues on data homogenization and station profiling. Only 25% of the breakpoints for rainfall coincided with station metadata, 36%, and 28% for maximum and minimum temperatures, respectively. Instrument issues and station relocations caused most inhomogeneities, while breakpoints due to natural causes, such as major volcanic activities, were disregarded in the analysis. The homogenized data have closely similar mean values and a lower standard deviation than the observed, especially the temperature data. The Mann-Kendall test revealed a warming trend for annual maximum (0.03°C/decade; p-value < 0.01) and minimum temperature (0.08°C/decade; p-value < 0.01), while homogenized rainfall has no significant trend (11.87 mm/decade; p-value = 0.097) from 1951-2022. This study produced long-term, quality-controlled, and homogenized data for climate change research and decision-making. The homogenized rainfall, maximum and minimum temperatures provide a better representation of the Philippine climate.