Increased severe landfall typhoons in China since 2004

Abstract

AbstractSevere landfall typhoons (SLTYs), defined as those with maximum sustained wind speed ≥41.5 m s−1 at landfalls, strongly affect the coastal regions of China and cause grave losses of life and property. In this study, we analyse the SLTYs in China in peak summer (July–September) for the period of 1973–2017, during which typhoon landfall intensity (LFI) experienced significantly abrupt strengthening in 1987 and 2003. The period is divided into three sub‐periods: period‐I (1973–1987), period‐II (1988–2003), and period‐III (2004–2017). It is found that the increase in LFI is dominated by the enhancement of intensification rate but not intensification duration. Meanwhile, the SLTYs in China have also abruptly increased since 2004, characterized by the count of about 65.9% (72.7%) of SLTYs in China (South China) in period‐III. Further analysis shows that the warming subsurface ocean heat content (OHC) over the northern South China Sea (SCS) plays a key role in modulating typhoon's intensification, which subsequently enhances the easterly steering flow leading typhoons to move westward. Low‐level water vapour convergence and vorticity are enhanced accompanied by warming northern SCS along the coastal region of southeastern China, resulting rapid typhoon intensification before landfall. About 9.7% of typhoons with landfall in South China experienced a rapid intensification process in 24 hr before landfalls in period‐III. However, the percentage is only 1.6 and 3.1% for period‐I and period‐II, respectively. The warming land surface over South China plays a minor role in attracting typhoons to landfall in South China, which named as “warmward landfall”. Overall, the abrupt enhancement of LFI and more SLTYs in China since 2004 are governed by the warming ocean, while the abnormal easterly steering flow and warming land surface over South China leading typhoons to move westward play a secondary role.