Divergent Trends in Meteorological and Agricultural Drought Over the 21st Century

Oral Presentation

Future changes in the terrestrial hydrological cycle may have severe consequences. In particular, 
decrease in growing season soil moisture (agricultural drought) poses a significant threat to food 
security, especially in the global south. For instance, in southern Africa and South America, 
agricultural drought is projected to worsen, even in areas where growing season precipitation 
increases or stays the same. Our study considers both historical variability and future change in the 
links between global precipitation and soil moisture - utilizing the ERA5 reanalysis and a large 
ensemble of CMIP6 models. We find that, whilst in the high latitudes discrepancies between trends 
in soil moisture and precipitation can be explained by changes in evapotranspiration, this is not the 
case in the arid and semi-arid tropics, where evapotranspiration is limited by water availability. In 
these regions, intensification of agricultural drought is associated with more pronounced dry-down 
of the land surface during the dry seasons, which is in turn driven by changes in seasonality and daily 
precipitation variability. Comparison between the tropics and the high latitudes thus reveals 
significant regional variability in the drivers of long-term change in soil moisture.