Increasing Threat of Landfalling Typhoons in the Western North Pacific between 1974 and 2013

Long-term changes between 1974 and 2013 were investigated in western North Pacific typhoons making landfall in East and Southeast Asia. Landfalling typhoon parameters, including the percentage of typhoons making landfall, the annual mean landfall intensity (LFI), and the annual accumulated power dissipation index at land, all increased significantly (at the 99% confidence level), by 14%, 17%, and 94%, respectively, over the study period. The increase in probability of a typhoon making landfall was attributed to an eastward shift of the typhoon genesis location. The LFI was decomposed into the product of the intensification rate and intensification duration. The product reproduced variations in the observed LFI well, and the correlation coefficient was high at 0.82. Although the intensification duration decreased slightly, an unprecedented increase in the intensification rate was observed, this increased the LFI. Warming of the upper ocean in the western North Pacific typhoon main intensification region, giving a higher tropical cyclone heat potential, yielded better oceanic conditions and overcame the worsening atmospheric conditions (increasing vertical wind shear), allowing typhoons to intensify. The increase in the annual accumulated power dissipation index was mainly caused by the increase in the LFI, and the annual number of typhoons and typhoon duration contributed much less. Increasing typhoon landfalling activities might heighten the threat posed by typhoons to populations and infrastructure in coastal regions.