Synergistic Satellite Assessment of Global Vegetation Health in Relation to ENSO-Induced Droughts and Pluvials

We used environmental metrics developed from multi-source satellite observations to quantify the global influence of El Niño-Southern Oscillation (ENSO) events on surface wetting and drying anomalies, and their impact on vegetation health. The environmental metrics included a microwave surface wetness index (ASWI) incorporating near-surface atmospheric vapor pressure deficit (VPD), volumetric soil moisture (VSM), and land surface fractional water cover (FW) derived from Advanced Microwave Scanning Radiometer (AMSR) observations, and the vegetation health index (VHI) derived from NOAA Advanced Very High Resolution Radiometer (AVHRR) observations. The combined ASWI and VHI analysis reveals complex ENSO related impacts on the distribution of water availability to plant communities, and variable vegetation sensitivity to associated drought and pluvial events. A delayed VHI response to changes in surface wetness (up to 3.4 months) was observed, whereby the ASWI may provide an effective forecast predictor of climate impacts on vegetation health. The intense 2015/2016 El Niño event coincided with strong ASWI and VHI latitudinal correspondence (R ≥ 0.73). The cascading impacts of climate anomalies on water cycle components and vegetation were further investigated over ENSO-sensitive sub-regions including Amazonia, Australia, southern Africa, and the South American Paraná delta region. The ASWI component information linked the effect of drought and pluvial events on vegetation health to underlying changes in surface water inundation, soil moisture and atmospheric moisture deficits. The new satellite-based assessments reveal the global complexity of ENSO-related impacts on surface water storages, and the influence of these climate and hydrologic perturbations on ecosystem productivity.