Changes in compound droughts-hot extremes across different timescales and their impact on soil moisture deficits

Compound drought and hot extremes (CDHEs) exert disproportionately larger impacts on natural systems and agriculture than individual climate extremes.  Existing research indicates that CDHEs are increasing in frequency and intensity, posing significant risks of severe agricultural drought and soil moisture exhaustion. However, the variations of CDHEs have been primarily studied at single timescales, leaving their multi-timescale characteristics and the resulting impacts on agricultural drought development poorly understood. We investigates the spatiotemporal evolution of CDHEs across different timescales using ERA5 reanalysis data and CMIP6 simulations. We then quantify the impacts of CDHEs on soil moisture, demonstrating that CDHEs significantly amplify the probability and severity of deficits in both surface and root-zone layers compared to independent droughts. Furthermore, the variability of the sensitivity of soil moisture deficits to CDHEs   over recent decades has been explored. These findings provide a comprehensive perspective on how compound extremes drive agricultural water stress across timescales, offering critical scientific support for developing robust early-warning systems and water management strategies in a warming climate.