Abstract
In this study, the standardized precipitation index (SPI) data in Hunan Province from 1961 to 2020 is adopted. Based on the critical slowing down theory, the moving t-test is firstly used to determine the time of drought-flood state transition in the Dongting Lake basin. Afterwards, by means of the variance and autocorrelation coefficient that characterize the phenomenon of critical slowing down, the early-warning signals indicating the drought-flood state in the Dongting Lake basin are explored. The results show that an obvious drought-to-flood (flood-to-drought) event occurred around 1993 (2003) in the Dongting Lake basin in recent 60 years. The critical slowing down phenomena of the increases in the variance and autocorrelation coefficient, which are detected 5–10 years in advance, can be considered as early-warning signals indicating the drought-flood state transition. Through the studies on the drought-flood state and related early-warning signals for the Dongting Lake basin, the reliabilities of the variance and autocorrelation coefficient-based early-warning signals for abrupt changes are demonstrated. It is expected that the wide application of this method could provide important scientific and technological support for disaster prevention and mitigation in the Dongting Lake basin, and even in the middle and lower reaches of the Yangtze River.
Highlights
The Dongting Lake basin is located in the middle reaches of the Yangtze River and the north of the southern Yangtze River, mainly covering the Hunan Province, which is known as a fertile land of fish and rice in China
Research on several real systems such as the climate system and the ecosystem has revealed that when the system approaches to the critical point, there will be a critical slowing down phenomenon featured by the slowing down in recovery rate, and the increases in the variance and autocorrelation coefficient after the system perturbation which provides a new idea for investigating the early-warning signals of abrupt changes in complex dynamical systems [14]
Since the mid-20th century, the drought-flood state transition over the Dongting Lake basin occurs more and more frequently under significant global warming, and correspondingly, the duration for the climate maintained in a drought or flood state is getting shorter and shorter
Summary
The Dongting Lake basin is located in the middle reaches of the Yangtze River and the north of the southern Yangtze River, mainly covering the Hunan Province, which is known as a fertile land of fish and rice in China. Research on several real systems such as the climate system and the ecosystem has revealed that when the system approaches to the critical point, there will be a critical slowing down phenomenon featured by the slowing down in recovery rate, and the increases in the variance and autocorrelation coefficient after the system perturbation which provides a new idea for investigating the early-warning signals of abrupt changes in complex dynamical systems [14]. Previous research on the early-warning signals of abrupt changes based on the critical slowing down theory can provide effective methods for the research on the early-warning signals of the drought-flood state transition over the Dongting Lake basin. By analyzing the variances and autocorrelation coefficients that characterize the phenomenon of critical slowing down, the early-warning signals for drought-flood state transition are explored which provides important reference for the prediction of drought and flood events over the Dongting Lake basin, thereby offering scientific and technological support for disaster prevention and mitigation over the basin
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