Author(s): Null
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Keywords: Runoff; ENSO; Climate index; Cross wavelet analysis; Source region of the Yangtze River
Abstract: As a water tower in Asia, the Qinghai-Tibet Plateau has been greatly affected by global climate change in recent decades. The main manifestations are rising temperature and continuous increase in runoff, which has continued till now. The ENSO (El Nino Southern Oscillation) event directly affects the tropical atmospheric circulation through the air-sea coupling, and the anomaly of the atmospheric circulation affects the monsoon over the Qinghai-Tibet Plateau, thereby further changing the temporal and spatial distribution of precipitation and runoff in the source region of the Yangtze River. Taking the source region of the Yangtze River as the research object, the runoff series measured at the Tuotuo River station and Zhimenda station were used to analyze the evolution of runoff at the two stations in the past 60 years. The response law of the high and low water change to ENSO events was studied, and the possible impact mechanism of ENSO events on runoff from the perspective of air-sea coupling affecting atmospheric circulation was revealed. The results indicated that both stations showed an oscillating upward trend, and in particular, the runoff showed a significant increase after 2000. By analyzing the response pattern of the high and low water change of the runoff in the source region of the Yangtze River during the ENSO event, it is found that the probability of low water runoff in the source region of the Yangtze River is higher in the warm event years from 1960 to 2000, both in the occurrence year and the following year. During cold event years, both stations showed a trend of low water runoff in the occurrence year while a similar probability of high or low water runoff in the following year. After 2000, the trend of high water runoff in the source region of the Yangtze River was particularly significant. Before 1960 and after 2000, the time-frequency structure between runoff and ENSO events in the source region of the Yangtze River had a certain degree of positive correlation. The occurrence of ENSO events caused latitudinal and longitudinal atmospheric circulation anomalies, which resulted in changes in oceanic heat and water vapor transport to the plateau, thus affecting precipitation and runoff on the Qinghai-Tibet Plateau. The results of the study provide a reference for revealing the mechanism of the influence of ENSO events on the water cycle in the source region of the Yangtze River.
Year: 2024