Characteristics of the tropical cyclones before making landfall in China

Abstract

Tropical cyclones (TCs) before landfall deserve great concerns, which directly affect the following forecasts and alarm‐issuing. In 1949–2021, nearly 29% of the total number of TCs that originated over the western North Pacific (WNP) and the South China Sea (SCS) made landfall in China. Of them, those from the WNP display a significantly lower (higher) ratio of making landfall over China (south China) in (the second year after) El Niño years. At 48 h before landfall, the TC centers display significant inter‐annual variations in zonal direction, but only those from the WNP additionally show significant inter‐decadal variations in meridional direction, which are probably attributed to the El Niño–Southern Oscillation and the large‐scale environment from both the ocean and the atmosphere. Once they move into a distance of ~660 km (~900 km) away from the south and southeast (east) coastlines of China, the probability of making landfall in the subsequent 24 h is increasing. In the 3 days before landfall, TCs show decreasing (increasing) uncertainty in translation speed (moving direction) as they moved close to the land, which is regardless of either the origination or the destination. In general, a moving direction of west‐northwestward dominates the majority of TCs if they originated from the WNP, which exhibits a clockwise rotation trend and tends to move faster as they approached the land. In comparison, those TCs originated from and stayed over the SCS show the largest uncertainty of moving direction and the most frequent abnormal tracks. For intensity (maximum wind speed), those originated from the WNP are generally stronger than those from the SCS. Their intensities vary in a range of −5 m s−1 to 5 m s−1 in each connective 6 h in the 3 days before landfall, of which the TCs made landfall in the east China display the largest uncertainty. In particular, great attention should be paid to the TCs originating from the WNP and approaching the southeast China in the future, in which the rapid intensification occurred with the most frequency but with a significantly lower occurrence in the second year after the El Niño years in the period investigated.