# Risk Assessment of Landfalling Tropical Cyclones in China Based on Hazard Risk Theory
## 3 Results and Discussion
### Hazard Analysis and Assessment of Causative Factors  
Based on data from the 1482 meteorological stations in provinces and cities affected by tropical cyclones from 1997 to 2021 during the frequent occurrence period of tropical cyclones (June to October), average daily wind speed, average daily maximum wind speed, and average daily maximum rainfall were recorded over 120 months. The IDW method was applied for spatial interpolation of wind speed data. For average daily rainfall, the ANUSPLIN interpolation method was employed using the latitude and longitude of the data stations as the main variables and terrain as a covariate, enabling the transformation of single-point data for regional analysis. Subsequently, Equation (5) was utilized to standardize the data, converting each indicator into the influence degree for assessment of the tropical cyclone hazard risk. Impact of each hazard causing factor indicator is shown in Figure 5.  
The hazard risk of tropical cyclones is the comprehensive result of the combined effects of strong winds and rainfall in the affected areas. Utilizing the standardized values calculated from three indicators (i.e., average daily rainfall, average daily wind speed, and average maximum wind speed) along with their respective weights in the hazard risk assessment of tropical cyclones (as calculated using Equation (7)), hazard scores were obtained. For ease of statistical analysis, the scores were multiplied by 100 for presentation. Subsequently, the hazard levels were classified using the natural breaks method in ArcGIS, as shown in Table 4. Employing graduated colors, the hazard risk of tropical cyclone-induced factors in various regions of China is depicted in Figure 6.  
Figure 5: Impact of each hazard causing factor indicator. (**a**) Average daily rainfall. (**b**) Average daily wind speed. (**c**) Average daily maximum wind speed. Based on the evaluation results (Figure 6), there were significant differences in the distribution of hazard risk factors among provinces in China. Cities in the southeastern regions of provinces such as Hainan, Guangdong, Fujian, Guangxi, and Zhejiang--including Haikou, Zhanjiang, Xiamen, Beihai, and Taizhou--were categorized as high-risk areas, with hazard levels rated as high or above. These areas experience frequent occurrences of tropical cyclones with high intensity, resulting in substantial impacts. The northeastern part of Zhejiang Province, the eastern part of Jiangsu Province, the Jiaodong Peninsula region in Shandong Province, and some areas in the northern part of Jiangxi Province exhibit high hazard levels. Most areas in Anhui Province, the eastern part of Shandong Province, and the central part of Liaoning Province, as well as Jilin and western parts of Heilongjiang Province, present moderate hazard levels. The remaining provinces show relatively low or minimal hazard levels. Overall, the hazard risk of tropical cyclone-induced factors in China tends to increase from north to south and from west to east. This trend is attributed to the frequent landfall of tropical cyclones along the southeastern coastal areas and the subsequent weakening of cyclones due to changes in underlying surfaces from ocean to land, as well as variations in terrain elevation and the presence of vegetation and structures. In some areas of Jiangxi Province, abundant precipitation contributes to increased hazard levels; meanwhile, in the central parts of Liaoning Province, Jilin, and the western parts of Heilongjiang Province, the influence of Mongolian cyclones results in persistently high av \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Level** & **Low** & **Relatively Low** & **Moderate** & **Relatively High** & **High** \\ \hline Scoring range (\(\times\)100) & H \(\leq\) 16.44 & 16.44 \(<\) H \(\leq\) 23.95 & 23.95 \(<\) H \(\leq\) 36.98 & 36.98 \(<\) H \(\leq\) 53.9 & 53.9 \(<\) H \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Hazard Score Table for Hazard-Causing Factors in the Impact Area of Tropical Cyclones.