ENSO-associated drivers of Philippine air temperature variability

Abstract:

The bulk of literature on El Niño-Southern Oscillation (ENSO) impacts in the Philippines deals with precipitation extremes and variability; few are relating ENSO with near-surface air temperature variability. While annual temperature ranges are comparatively smaller for the Tropics, prolonged elevated temperatures can be detrimental to the agricultural sector. Thus we present here the ENSO-related atmospheric drivers of the seasonal evolution of daily mean, maximum, and minimum near-surface air temperature in the Philippines. Mean temperature from the Asian Precipitation - Highly-Resolved Observational Data Integration Towards Evaluation (APHRODITE) along with extreme temperature from the Climate Research Unit (CRU) are chosen as gridded observational datasets. Atmospheric fields from the latest reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF), ERA5, are taken from 1979 to 2015. The dominant modes of the seasonal evolution of the near-surface air temperature and atmospheric fields are obtained using the extended empirical orthogonal function (EEOF) analysis. The first two dominant mean temperature modes are moderately correlated with the Extended Reconstructed Sea Surface Temperature version 5 (ERSSTv5) Oceanic Niño Index (ONI). The leading EEOF is related to non-ENSO outgoing longwave radiation and the second EEOF is associated with ENSO-modulated convective activity. The leading maximum temperature EEOF is highly correlated with ONI, through the East Asian Winter Monsoon (EAWM) surface latent heating from December to February. Only the third minimum temperature EEOF is significantly correlated with ONI, where ENSO-associated convection influences the post-maturity March-April-May minimum temperature. By understanding the mechanism of seasonal temperature variability, both the populace and the farmlands can be better prepared in the coming ENSO events, more so needed as a nation highly vulnerable to climate change impacts.