Solar‐Induced Chlorophyll Fluorescence Yield Holds the Potential for Drought Early Warning

Abstract Early detection of emerging agricultural drought conditions is challenging but crucial for ensuring sustainable agriculture and global food security. Existing drought early warning systems utilize hydrometeorological or greenness‐based vegetation indicators. We propose that spaceborne measurements of solar‐induced chlorophyll fluorescence (SIF) yield (SIFyield), which is SIF normalized by absorbed photosynthetically active radiation (APAR), have the potential for early detection of emerging crop stress conditions. We evaluate meteorological (Standardized Precipitation Evapotranspiration Index (SPEI)), hydrological (root zone soil moisture (RZSM)), and physiological (SIF, and SIFyield) vegetation stress indicators to monitor the onset of crop stress indicated by reductions in gross primary productivity (GPP). Empirical Orthogonal Function and causal analysis indicate SIFyield has the strongest positive correlation with GPP, lagging by 1–2 months compared to other indicators. With its long lead time, space‐borne SIFyield can serve as an early indicator for agricultural drought onset, aiding global agricultural management efforts.