A shift in drought propagation trend in the Yellow River Basin during 1980–2020 linked to climate change and vegetation greening

Study region: Yellow River Basin Study focus: Meteorological drought triggers soil moisture drought, increasing likelihood of extreme events and causing detrimental impacts on ecological systems and human society. The Yellow River Basin (YRB), which has been prone to recurrent droughts, has recently experienced extensive vegetation greening and climate change. However, it remains unclear whether climatic variability and vegetation greening will affect drought propagation, particularly duration extension that is associated with drought intensification and early warning. Therefore, we quantitatively investigated propagation time (PT) and drought duration ratio (DDR), explored propagation dynamics in the YRB during 1980–2020. New hydrological insights for the region: The results indicated a significant portion of regions exhibited PT ranging from 1 to 2 months, with shorter PT in the middle reaches. Larger DDR (over 2) was concentrated in the Loess Plateau, indicating a greater degree of drought extension. A shift around 2000 in propagation dynamics was observed. PT shifted from a shortening trend to a prolonging trend, while DDR shifted from an increase to a decrease. The shift was closely related to increasing impacts of greening, with the proportion of PT and DDR driven by NDVI reached to 23.64 %–29.30 % and 20.80 %–23.16 % after 2000, respectively. Overall, our results highlight the necessity of temporal characteristics and vegetation effects into addressing drought impacts and risks in the similar arid and semi-arid regions globally.