Impact of landfalling tropical cyclones in mainland China

Tropical cyclones (TCs) have a significant impact on mainland China. The purpose of this study is to develop an impact index which correlates with both the strong wind and heavy rainfall/flood damage caused by TCs in mainland China. By considering the radius of TCs, we first define the total destructiveness index (TDI) and total column water vapor index (TVI). Economic loss is used to represent the impact of landfalling TCs. The analysis is based on 30 landfalling TCs between 2001 and 2007, and identified significant correlations between the impact of landfalling TCs and the TVI (TDI). The correlations between the impact of landfalling TCs and TVI, TDI and maximum wind speed of TCs before landfall are 0.751, 0.59 and 0.345, respectively. This study also shows that landfalling TCs with a higher TVI usually bring heavier rainfall, and result in more economic losses in China. A TC impact index is defined as a function of TVI and TDI. The correlation between TC impact index and economic loss was found to be significant (r=0.769). Tropical storm Bilis in 2006 is classified as the landfalling TC with the highest impact index between 2001 and 2007 and Matsa, in 2005, as the second highest impact index in this same interval. Using a system cluster analysis method, 30 landfalling TCs in this study were graded into five categories according to their impact indices. Category 5, which is the highest level, included only one TC, which constituted 4% of the total TCs studied. Category 4 included three TCs (10%). Categories 3 and 2 included seven TCs each (23%) and Category 1 included 12 TCs (40%).