Identification Of Socio-Economic Exposure Patterns And Damage Assessment In Tropical Cyclones

Tropical cyclones are one of the most destructive natural disasters.Rapid environmental changes have expanded the impact range and severity of tropical cyclones,leading to frequent catastrophic events.The urbanization process has led to population and wealth accumulation and growth,increased tropical cyclone losses,and increasing tropical cyclone risks,which have become huge challenges for sustainable development in coastal areas and countries.Exposure is an important component of disaster risk and one of the key factors for risk management.At the same time,quantitatively describing the causes of tropical cyclone disaster losses and the spatiotemporal characteristics of catastrophic events losses can provide important support for risk management.Therefore,determining the socio-economic exposure hotspots and causes of losses of tropical cyclones is crucial for reducing the risk of tropical cyclones and minimizing losses.This study is based on socio-economic data data,tropical cyclone track data,and tropical cyclone loss data,and uses a series of spatial pattern analysis methods and factor analysis methods to construct a global tropical cyclone wind field model,identify the exposure hotspots of tropical cyclones at a global scale,reveal the main influencing factors of global tropical cyclone losses,as well as the spatiotemporal and causes of tropical cyclone catastrophic losses.The main research work and conclusions are as follows:(1)This study constructed a global tropical cyclone hazard map for 1990-2019based on tropical cyclone track data and the Holland wind field model,determining the affected countries and areas by tropical cyclones.Simultaneously,tropical cyclone wind fields were simulated for different return periods(50-year,100-year,250-year,and 500-year events)and classified into three scales of hazard(S1,S2,and S3)from low to high.The results indicate that the hazard map from 1990 to 2019 showed a total of 55 countries worldwide affected by tropical cyclones,with an affected area of 1304.9x 10~4 km~2.Among them,the East Asia and Pacific region has the largest area affected by tropical cyclones(925.87 x 10~4 km~2),accounting for 73%of the total affected area.Overall,the wind speed classification of tropical cyclones decreases from the coast to the inland.At the same time,with the increase of return period,the affected area of tropical cyclones shows a gradually inland expansion and the higher the wind speed classification,the faster the growth rate.From once in 50 years to once in 500 years of return period,the global area affected by tropical cyclones increased by 120.6×10~4km~2.And the S3 is also gradually expanding into inland areas,with a higher growth rate in the area compared to the other two scales.(2)Based on the obtained of the tropical cyclone hazard map,the exposed population and GDP from 1990 to 2019 and under different return periods are extracted using population and GDP data.The spatiotemporal variation characteristics changes of the global exposed population and GDP of tropical cyclones are calculated by using the change rate and population distribution index.The results show that from 1990 to2019,the hazard level based on 1990-2019 as the base period,the exposed GDP increased by 977.5 billion US dollars,the exposed population increased by 550 million,and the exposed population presents a clustered distribution feature.The annual average growth rates of exposed GDP and exposed population are 3.62%and 1.26%,respectively.The annual average growth rates of exposed population and GDP under S3 level are the largest.From the regional perspective,East Asia and the Pacific region and South Asia show an increasing trend in exposed GDP and exposed population.Among them,the increase in exposed GDP in East Asia and the Pacific region is the largest,accounting for 41.67%of the global tropical cyclone exposed GDP increase.The increase in exposed population in South Asia is the largest,reaching 2.08 billion,accounting for 37.80%of the total exposed population increase.At the same time,from the 50-year to 500-year return period,the exposed GDP increased by 43.755 billion USD,and the exposed population increased by 181 million,with the exposed population growth in S3 region being greater than other regions.(3)Based on the extracted exposure population and GDP,the wind speed weight is generated using game theory principles,and the absolute exposure index and relative exposure index are constructed to form the social-economic exposure matrix of tropical cyclones,in order to explain the patterns and hotspots of social-economic exposure to tropical cyclones.There are 8 countries with exposure GDP and population at level V(the highest level in the exposure matrix)and 10 countries with exposure population at level V,mainly located in East Asia and the Pacific region.Korea,Vietnam,the Dominican Republic,the Philippines,and Japan are both countries with exposure GDP and population at level V,which are the hotspot areas for exposure.(4)Tropical cyclones cause significant losses every year.Identifying the main factors that contribute to these losses is crucial for managing the risks associated with tropical cyclones.Based on the risk triangle theory,an attribution analysis is conducted on the direct economic losses and fatalities of tropical cyclones worldwide from 1990to 2019,based on the three risk factors of hazard,socio-economic exposure,and vulnerability.The results show that the direct economic losses,intensity of tropical cyclone hazards,and exposed population worldwide have all increased,while the death of tropical cyclone,vulnerability of the population and economy have decreased.Among the three factors,the hazard is the main driver of losses.Therefore,apart from the hazard,the death toll is mainly influenced by the exposed population,and the direct economic losses are affected by the vulnerability.Methods can be taken to reduce losses by decreasing exposure and vulnerability.(5)The country with the largest population index of deaths caused by tropical cyclones,1990-2019,was China.Therefore,combined with factors such as the availability of data,this article takes the catastrophic tropical cyclones in China from2009 to 2019 as typical cases to reveal the spatiotemporal characteristics and causes of catastrophic losses.Based on the improved G-index,spatial autocorrelation,cold and hot spot analysis and other methods,the overall characteristics,spatial pattern and main influencing factors of the catastrophic losses of tropical cyclones landing on Chinese Mainland from 2009 to 2019 were studied.The results show that from 2009 to 2019,a total of 18 tropical cyclone catastrophes affected 17 provinces and regions in China,with the affected areas of light,medium,heavy,and extremely heavy losses accounting for 37.68%,44.16%,13.84%,and 4.32%.The disaster has a strong spatial aggregation.In addition,the impact of exposed population,maximum wind speed,and maximum cumulative precipitation process on typhoon disaster losses shows a positive correlation,while the impact of exposed GDP(gross domestic product)on disaster losses shows a weak negative correlation.This study identifies the hotspot areas of typhoon disasters and emphasizes the importance of formulating effective disaster reduction measures and building disaster resilience.In conclusion,this study constructed an exposure model for global tropical cyclones based on the Holland wind field model,combined with population and GDP data,identified the spatiotemporal patterns and hotspot regions of social and economic exposure to global tropical cyclones.At the same time,based on the three elements of risk,the attribution analysis of losses caused by global tropical cyclones was conducted,and the main hard factors of tropical cyclone losses were determined.Finally,using the case of China’s tropical cyclone catastrophe,the spatiotemporal characteristics and influencing factors of tropical cyclone catastrophe losses were analyzed.The research findings provide policy recommendations for risk management of global-scale tropical cyclones and theoretical basis for the prevention and response to tropical cyclone catastrophes.