No abstract

The evolution of the frequency of dry/wet spells is a hot topic in global climate change research. The synergistic effects of dry/wet spells make their consequences far more significant than a single disaster, having considerable impacts on hydrology, ecology, and economies, especially in the context of global warming. In this study, the standardized precipitation evapotranspiration index (SPEI)-based identification of dry/wet spells was used to explore the evolution of the frequency of dry/wet abrupt alternation (DWAA) events in the past four decades in China, makes up for the lack of research on the evolution of such compound disasters. China has been affected by dry/wet spells in many areas for a long time. Studies found that high-frequency DWAA areas are concentrated in densely populated areas, China's essential food bases and core areas for economic development. Dry-to-wet (D-W) events and wet-to-dry (W-D) events basically increased or decreased at the same pace in this period. We innovatively find DWAA events (D-W events and W-D events) are projected to occur increasingly in a wider region of China. The frequency of D-W events across China has increased from 2.35 in the 1980s to 3.56 in the last decade, a 50% increase. On the other hand, W-D events increased from 2.6 to 3.23, increasing 24%. The three regions with the most remarkable changes in the past four decades are Inner Mongolia, northwest China, and north China, where D-W events increased by 121, 61, and 58%, respectively, and W-D events increased by 71, 57, and 61%, respectively. Hereby, it is vital to implement effective prevention against DWAA events in the area which has been neglected in the past decades because of lower frequency. These results may help policymakers develop suitable disaster mitigation plans for reducing the potential risks of extreme compound natural events.

Tropical cyclone disasters frequently occur in the southeastern coastal areas of China, and the concentration of population and economy has further increased the risk of tropical cyclone disasters in this region. The effects of tropical cyclones on populations involve a complex interaction between hazard intensity, environmental factors, exposure level, and fortification capacity. Therefore, quantifying the relationship among these factors is imperative for early warnings, risk assessments, and mitigation strategies for tropical cyclone disasters. In this study, a comprehensive tropical cyclone quantitative risk assessment approach considering the joint relation between strong wind and extreme precipitation and environmental, exposure and fortification factors was developed using the generalized additive model (GAM) and copula function for the case of Hainan province, China. The 10 min maximum wind speed (MW), maximum daily rainfall (MR), elevation (ELE), total population (POP), and time (t) were ultimately selected by the GAM as explanatory variables for the affected population rate (APR). A 50% increase in the MW produced a 48.779%–82.657% increase in the APR, a 50% increase in the MR produced a 19.534%–25.631% increase in the APR, and a 50% increase in the POP produced a 0.796%–15.193% decrease in the APR. The APR obviously increased with the return period increase in Hainan province. The APR of cites (counties) ranged from 0.443 to 0.632 for a once‐in‐10‐year return period and ranged from 0.518 to 0.829 for a once‐in‐50‐year return period.

No abstract

Floods that cause yearly economic losses and casualties have increased in frequency with global warming. Assessing the mortality risks of populations due to flooding is important and necessary for risk management and disaster reduction. Thus, this paper develops a method for assessing global mortality risks due to river flooding. Global historical annual death tolls are first estimated during the historical period 1986–2005 (T0) by using available mortality vulnerability functions of river flooding. Then, the best vulnerability function is selected according to lower root mean square errors (RMSE) and the differences in the multi-year mean (DMYM) values. Next, the adjustment coefficient K c for each country (region) is calculated to use in the revision of the selected vulnerability function. Finally, the mortality risks are estimated based on an adjusted vulnerability function. As a case, the paper assessed and analysed the global mortality risks due to river flooding during 2016–2035 (2030s) and 2046–2065 (2050s) for the combined scenario of the Representative Concentration Pathway 4.5 (RCP4.5) and the Shared Socioeconomic Pathway 2 (SSP2), and the RCP8.5-SSP5 scenario. The results show that the estimation errors of the death tolls in most countries (regions) decrease after adjusting the vulnerability function. Under the current defense capacity and vulnerability level, the average annual death tolls of RCP4.5-SSP2 and RCP8.5-SSP5 in the 2030s will increase by 1.05 times and 0.93 times compared with the historical period. They will increase 1.89 and 2.20 times, respectively for the two scenarios during 2050s. High-risk areas are distributed in the south-eastern Eurasia.