Interannual and interdecadal variations in typhoon tracks around Japan

摘要

This study employs Geographical Information Systems software to develop a classification system for typhoons (TYs) affecting Japan (1951-2011) and uses that system to investigate the spatial and temporal variations of storm tracks and their connection to the location and strength of the North Pacific subtropical high (NPSH). TYs coming within a 300-km buffer zone around the four main islands of Japan (JZOI) are grouped into two main types: those that remain on the Pacific Coast (PC) and those that enter the Japan Sea (JS). Results indicate that fewer TYs enter the JZOI when the NPSH extends strongly to the west and more reach Japan when it extends to the northwest. The winds around the periphery of the NPSH affect the recurvature of TYs directing them either west towards the China Mainland or around the western edge of the high towards Japan. More importantly, during periods when greater numbers of TYs affect the PC side of Japan (PC+), the NPSH extends to the southwest. However, during periods when greater numbers of TYs affect JS side of Japan (JS+), the NPSH extends to the northwest closer to Japan. The southwest extension of the NPSH enables TYs to recurve and pass to the eastern side (PC) of Japan while the northwest extension forces TYs around or across Japan into the JS. An important finding is that the moderately different positions of the NPSH change the atmospheric circulation around Japan dramatically and affect whether TYs pass over the PC side or the JS coast side of Japan. At the interannual time scale, increased JS+ years were observed since 1980 because of the frequent occurrence of the Pacific-Japan pattern. We also found that at the interdecadal time scale, PC+ years have increased due to the southwestward extension of the NPSH since 1980.