No significant increase in storm intensity; Vietnam

Hiroshi Takagi. Statistics on typhoon landfalls in Vietnam: Can recent increases in economic damage be attributed to storm trends? Urban Climate, Volume 30, December 2019, 100506

The Emergency Events Database (EM-DAT) indicates that the economic damage associated with storms has been rapidly growing in Vietnam. By contrast, the fatality rate due to storm-relevant disasters has been declining in recent decades. This study investigates whether typhoon trends have affected these outcomes. Best track data from the Japan Meteorological Agency (JMA) were examined to estimate central pressure and wind speed when typhoons made landfall. From 1977 to 2017, typhoons with wind speeds above 20 knots struck the country 105 times. A statistical analysis, which defined a storm’s intensity using principal component analysis (PCA), revealed that Typhoon Doksuri in 2017 was the strongest among the collection, followed by Cecil in 1985, Xangsane in 2006, and Damrey in 2017. The worst storm in history, Typhoon Linda in 1997, claimed over 3500 lives in southern Vietnam, but was only ranked 37th, demonstrating that typhoon intensity is not always the determining factor of fatalities. Moreover, the analysis of variance (ANOVA) illustrates that none of the meteorological trends such as frequency, central pressure, wind speed, or storm intensity show any significant increase or decrease over the last four decades. However, landfall frequency has risen significantly, particularly in the northernmost part of the country where two large cities, Hanoi and Hai Phong, are located. A strong correlation was found between intensity and recent economic damage (r = 0.80) based on the proposed index of positive annual landfall storm intensity (PALSI). Given all of these factors, it is reasonable to attribute the expansion of disaster-related economic damage to economic development and the fundamental volatility of typhoons.

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