Spatiotemporal evolution of drought-flood patterns in Eastern China over past 550 years and future projections

Abstract

[Objective] The eastern region of China exhibits high drought-flood variability and faces significant disaster risks.However, the evolution of drought-flood patterns based on long-term historical data remains unclear. The aim is to reveal the long-term evolution and future trends of drought-flood patterns in eastern China. [Methods] Based on long-term meteorological data from 1470 to 2020 in China, a drought-flood level series was reconstructed. Wavelet analysis and power spectrum analysis were applied to identify the dominant cycles and stage characteristics, and a long short-term memory( LSTM) model was employed to predict the drought-flood evolution trends in eastern China from 2030 to 2100. [Results] The result showed that between 1470 and 2020, eastern China experienced two predominantly dry periods and one predominantly wet period. The drought-flood conditions exhibited variation cycles averaging 20, 50, and 180 years. The “wet north-dry south” and “dry northwet south” climate patterns alternated with an average cycle of 200 years. Spatial analysis showed that over the past 50 years,regions such as North China and the southwestern part of Northeast China have high drought-flood variability, with large interannual variance thresholds, indicating an unstable climate system. In contrast, most southern regions exhibited low variability and more stable drought-flood variations. Machine learning prediction result indicated that after the mid-21st century,the climate pattern of eastern China would shift from predominantly dry to predominantly wet. Since the late 20th century, the frequency of “wet north-dry south” events had gradually increased, reaching a phase of high occurrence around 2036, followed by a gradual decline. In contrast, “dry north-wet south” events were expected to gradually intensify afterward, reaching a phase of high occurrence in the mid-21st century before gradually decreasing. [Conclusion] The result indicate that drought-flood conditions and north-south drought-flood patterns in eastern China exhibit long-term periodicity and alternating phases. In the future, the climate system may show a transitional trend from predominantly dry to predominantly wet conditions. These findings deepen the understanding of the spatiotemporal evolution mechanisms of drought and flood in eastern China and provide scientific support for optimizing water resource allocation, assessing drought and flood disaster risks, and constructing defense systems.This is of great significance for ensuring regional water security.

Keywords

drought-flood variation / north-south drought-flood patterns / wavelet analysis / long time scale / LSTM model