How 2022 extreme drought influences the spatiotemporal variations of terrestrial water storage in the Yangtze River Catchment: Insights from GRACE-based drought severity index and in-situ measurements

Under global warming, extreme climatic events frequently occurred worldwide such as extreme drought and heavy flood. Analysis of drought and flood spatiotemporal evolution and physical mechanism is of great significance for future disaster warning and mitigation. In 2022, the Yangtze River Catchment (YRC) experienced an extreme drought, which profoundly affected the regional economy, ecological environment and anthropogenic activities. In this study, we quantified the spatiotemporal characteristics of terrestrial water storage anomalies (TWSA) response to this severe drought event using Gravity Recovery and Climate Experiment-based drought severity index (GRACE-DSI), with the inspection of hydrological model and in-situ measurements. The results showed that the 2022 YRC drought first occurred in July at the upstream and midstream, then spread to downstream and finally occupied almost the whole YRC in August and ∼ 94% of the YRC in September. The effectiveness of GRACE-DSI for drought monitor can be validated by in-situ hydrological and meteorological observations. Good correlations among El Niño-Southern Oscillation (ENSO), precipitation anomalies (PA), and TWSA were found, demonstrating the regional atmospheric circulation anomaly was the driving factor of this extreme drought event, which triggered the changes in precipitation further to influence the pattern of terrestrial water storage. The consecutive La Niña events induced the extension of western Pacific subtropical high (WPSH) and Iranian high, the precipitation deficiency in 2022 summer declined by ∼ 46% and ∼ 36% compared to 2020 and 2021 respectively, which was the main cause of the extreme drought.