Abnormal depletion of terrestrial water storage and crustal uplift owing to the 2019 drought in Yunnan, China

Abstract

SUMMARYDroughts are natural disasters that cause severe economic and social impacts. Analysing changes in terrestrial water storage (TWS) before and after typical drought events is important for understanding the principles of the regional terrestrial water transport law and drought response, and for providing scientific agricultural production guidance. Yunnan is a drought-prone region, and high temperatures and low rainfall in 2019 led to a severe drought. Precipitation data showed that the wet season in Yunnan started 1 month later than usual in 2019. Moreover, 52 per cent (205 000 km2) of the total area of Yunnan experienced a cumulative precipitation anomaly (PA; in percentage) of −30 per cent between January and May. In this study, we used data from the Gravity Recovery and Climate Experiment (GRACE) and Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) missions to identify the spatial and temporal variations in TWS before and after the 2019 drought. Our results show that the drought led to an average reduction of 125 mm (equivalent water height) in the TWS, with the greatest loss in southern Yunnan, with a maximum loss of 272 mm. The reduced TWS caused by the delayed and anomalously weak southwest monsoon in 2019 gradually spread from the southwest to the northeast. By comparing with the drought in 2009–2010, we find that the southern Yunnan with abundant rainfall is more vulnerable to drought and has a relatively larger deficit in TWS. Furthermore, we used GRACE and GRACE-FO data to invert the crustal uplift caused by terrestrial water unloading in the 2019 drought, and found a maximum uplift of 8.4 mm. This showed a consistent spatial distribution with displacement variations recorded by 26 continuous Global Positioning System (GPS) stations in Yunnan during the same period, albeit slightly different in magnitude, indicating the potential of GPS for monitoring regional TWS changes.