Impact of large-scale climate factors on flood disasters in China in the past 40 years

Based on 0.5°×0.5° daily precipitation data and EM-DAT data across China from 1980–2018, this paper analyzed the impact of El Niño Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO) on the frequency and intensity of extreme precipitation, flood occurrence and flood damage. The findings indicate that when El Niño occurs in winter, the intensity of extreme precipitation in autumn in the eastern coastal areas of China, and the lower reaches areas of the Yellow and the Yangtze Rivers, will increase by 26% in the following year. When La Niña occurs in winter, the intensity of extreme precipitations in spring and summer in eastern China will increase by 8.8% and 5.1% respectively in the following year. When NAO is in a positive phase, the frequency of extreme precipitations in spring, summer and autumn is relatively high in most areas of China, and the intensity of summer extreme precipitations in East China increases by 8.5%. Compared with normal years, after the occurrence of El Niño or La Niña in winter, the flood damage increases by 14.5% in spring, while the flood occurrence decreases by 30% in autumn in the following year. When NAO is in a positive phase, the flood damage is reduced by 20% in the spring, while the flood occurrence increases by 14% in autumn. After the occurrence of La Niña and the positive and negative phases of NAO, the changes in extreme precipitations and flood disasters in the Yangtze, Yellow and Pearl River basins of China are consistent．