Summertime ENSO potentially amplifies rainstorm and flood risk in the lower Yellow River Basin, China

Abstract

Study region: The Yellow River Basin (YRB) in China. Study focus: Ecological conservation and high-quality development of the YRB have been incorporated into the national strategy of China. Here we investigated into the impacts of El Nino-Southern Oscillation (ENSO) on rainstorm and flood risk in the YRB, paid special attention to disaster-induced losses and explained the mechanisms of ENSO affecting the risk. New hydrological insights for the region: ENSO tends to amplify rainstorm and flood risk in the YRB due to the increase in rainstorm days (rainstorm amount) by 33.6 % (34.1 %) in the next year with the previous summertime El Nino, by 20.3 % (19.3 %) in the current year with summertime La Nina, and by 70.7 % (72.5 %) in the ENSO phase shift year, and leads to a marked increase in disaster-induced losses. The summertime La Nina (El Nino) can increase the annual extreme runoff amount by 25.8 % (decrease by 8.4 %) in the lower YRB in the current year. At 500hpa, the higher air pressure over Eastern Europe and Okhotsk Sea in July, and the higher air pressure over the northern Eurasian continent and the lower air pressure over Lake Baikal and Balkhash in August tend to amplify rainstorm and flood risk. At 850hpa, the increase of water vapor transport from the south and cold air activities in high latitudes tend to increase the risk.

Keywords

• ENSO
• Rainstorm and flood risk
• Maximum covariance analysis
• Disaster-induced losses
• Atmospheric circulation