Interdecadal changes of tropical cyclone intensity in the South China Sea

This study investigates the interdecadal changes in the intensity of tropical cyclones (TCs) formed within or entered the South China Sea (SCS) in the TC season (June to November) during 1977–2018. Based on change-point detection in five TC datasets, two high-intensity periods [period 1 (P1): 1977–1993; and period 3 (P3): 2006–2018] and a low-intensity period [period 2 (P2): 1994–2002] were identified. Genesis location and vertical moisture advection dominate the interdecadal changes in TC intensity. TC genesis locations in P1 and P3 shift more eastward than in P2. Statistical analysis shows that the farther east the genesis is located, the longer the intensification duration and the higher the intensity the TC can reach. It is also found that environmental factors around the TC tracks are the other reason for the TC intensity. TCs in P2 pass through the region with adverse environmental conditions more frequently. Mid-level relative humidity and vertical motion are key environmental factors for TC intensity. Genesis location is regulated by the Pacific decadal oscillation, the north Indian Ocean SST and the Atlantic multidecadal oscillation. Atmospheric circulations in the tropical Indian Ocean and SCS affect vertical motion. The results provide some helpful insights into the variation of SCS TC intensity.