Assessing the coherency of different El Niño events with vegetation health using time-series remote sensing data and wavelet coherency analysis in part of Southeast Asia

Abstract

El Niño Southern Oscillation (ENSO) is a cyclic period of warm and cold events that affect the seasonal global weather patterns due to the weaker trade winds in Pacific Oceans. During the warm ENSO events, or El Niño, regions including Southeast Asia, are exposed to the reduced precipitation and warmer temperatures, which able to affect the vegetation dynamics. El Niño warm events can occur in different magnitudes and intensities but the impacts of different warm ENSO magnitudes to vegetation health is rarely studied. This study explored the coherency of different El Niño events as indicated by ENSO indices with vegetation health in Indonesia by using wavelet semblance analysis (WSA). Our results suggested that short-duration and strong ENSO events highly affected the vegetation dynamics, and potential coupled impact of ENSO warm event and Indian Ocean Dipole (IOD) such as in 2006 can influence the vegetation health. The 1982, 1997–1998 and 2015–2016 strong ENSO events affected for more than 40 % of vegetation health in Indonesia, while 2006's combined weak-ENSO and IOD events affected up to 44 % of vegetation health. From the total 40–59 % areas that were affected in 1997–1998 ENSO's event, 38–56 % was Evergreen Broadleaf Forests (EBF). This indicates that strong magnitude of El Niño combined with IOD could increase the impact of climate anomalies to the vegetation health.