Spatial-temporal characteristics of drought and flood disasters in Yunnan Province on the margin of the Tibetan Plateau over the past 620 years

Drought and flood disasters (DFD) are the most important natural disasters in the Indian monsoon (IM) region, and often occur in the same year. This makes it difficult to accurately study the characteristics of DFD using the evaluation grades of disasters. Based on the statistical analysis of historical drought and flood data in Yunnan Province, combined with anomaly accumulation values, sliding t tests and wavelet analyses, the spatial-temporal characteristics and the possible dynamic mechanisms of the DFD in Yunnan Province are analysed during the past 620 years. The results show that the frequency of flood disasters in Yunnan Province was slightly higher than that of drought disasters, and disaster frequency has gradually increased over the past 620 years, especially after 1750 AD. The variations characteristics of the drought and flood index (DFI) have 2 similar to 10 year quasi-periodic signal in the east and west regions of the Yunling-Ailao Mountains, and they are consistent with the environmental records of tree rings and lacustrine deposits in the region. The DFD of the IM region may be influenced mainly by solar activity and El Nino-Southern Oscillation (ENSO) on a century scale, and frequent human activities enhance the impact of DFD, especially in the east region of the Yunling-Ailao Mountains. The results provide a method to further understand the mechanism and trends of drought and flood disasters in the monsoon region on a century scale.