Satellite Remote Sensing of Post-Extreme Rainfall Eco-hydrological Changes and Vegetation Productivity in Hyper-Arid Landscapes

Extreme rainfall events across the United Arab Emirates (UAE) in 2024 provided a unique opportunity to investigate rainfall-driven eco-hydrological responses in hyper-arid landscapes using satellite remote sensing. In these water-limited ecosystems, surface water availability strongly constrains vegetation productivity and ecosystem carbon uptake, yet the impacts of episodic rainfall events remain poorly understood. This study integrates multiple satellite observations from Landsat, SMAP (Soil Moisture Active Passive), OCO-2 (Orbiting Carbon Observatory-2), MODIS (Moderate Resolution Imaging Spectrometer), AMSR-2 (Advanced Microwave Scanning Radiometer 2), and GRACE to quantify changes in vegetation greenness, evapotranspiration (ET), surface soil moisture (SFSM), land cover, Vegetation Optical Depth (VOD), Solar-Induced chlorophyll Fluorescence (SIF), and terrestrial water storage (TWS) following anomalously wet conditions in Al Ain, UAE. Daily precipitation at Al Ain international airport station was compared against satellite-derived hydrological variables and showed good agreement. Previous studies in Al Ain regions have also demonstrated a favorable correlation between in situ surface soil moisture measurements and SMAP SFSM. The results showed rapid and consistent increases in vegetation activity and eco-hydrological responses after a rainfall event. Over the past decade, 2024 exhibited the highest vegetation greenness across the study area, accompanied by a notable land cover shift characterized by an approximately 3% expansion in grass cover extent, which had previously remained relatively stable. Enhanced vegetation productivity was further supported by elevated GOSIF (Global OCO-2 SIF) Gross Primary Productivity (GPP), reaching approximately 292 g C m⁻² yr⁻¹, together with increased microwave VOD, indicating greater vegetation water content and biomass dynamics. These findings demonstrate the strong sensitivity of eco-hydrological processes and ecosystem carbon cycling to episodic rainfall events in hyper-arid climate zones. The widespread and persistent vegetation response observed under extreme climatic conditions highlights the capacity of short-term increases in water availability to rapidly alter ecosystem functioning and carbon uptake, even within a single year.