GRACE and land surface models reveal severe drought in eastern China in 2019

An extreme drought on record occurred in eastern China in 2019 and caused severe terrestrial water storage (TWS) deficits. It is important to understand this drought process and assess its impacts. We combine the Gravity Recovery and Climate Experiment (GRACE) observations and land surface model (LSM) outputs to thoroughly investigate this drought event. To consolidate the quantitative analysis, we fuse five sets of GRACE-derived TWS data and four sets of LSM-based soil moisture storage (SMS) data, respectively, using the generalized three-cornered hat method and the least-square method, and thereby generate robust TWS and SMS results. Both the GRACE and LSM results suggest that this drought event started in July in northeastern and northern China and then spread south to southern China in August and lasted until December, influencing a vast area of ∼2.0 × 10⁶ km² in eastern China. The drought center first appeared in North China, then moved southward to the middle and lower reaches of the Yangtze River basin, and finally stayed in South China. TWS results from GRACE show that the largest regional TWS deficit was 94.1 ± 17.7 mm and happened in September in the middle and lower reaches of the Yangtze River basin. SMS results from LSMs exhibit similar spatiotemporal characteristics to the GRACE results but with smaller magnitudes. Meteorological Drought Composite Index from the China Meteorological Administration agrees well with the GRACE-derived TWS deficits and LSM-based SMS deficits in terms of their spatiotemporal distributions. These three independent indicators together identify and assess this severe drought event, providing us a quantitative understanding of it. The water budget analysis demonstrates that the precipitation deficit in the second half of 2019 is the main reason for this drought event. The precipitation deficit is mainly due to the northerly wind anomaly and sinking anomaly over eastern China, which are closely associated with the anomalous cyclonic circulation over the western Pacific.