Comparative analysis of extreme events of tropical cyclones in the Northwest Pacific Ocean

Two tropical cyclone (TC) events generated in the Northwest Pacific (WNP) in 2004 and 2017 were selected to study their track patterns, landfall locations, intensities and related environmental factors. The number of TCs and the number of landfalls were basically the same in these two years, but the landfall locations (east and south China, respectively) and accumulated cyclone energy (ACE) were different. The results showed that the WNP TCs were strongly influenced by regional sea surface temperature (SST) anomalies, El Niño-Southern Oscillation (ENSO) and snow cover on Qinghai and Tibetan Plateau (QTPSC) anomalies. The number of TCs in the regional high SST areas increased, and the TC track patterns changed with their generation locations, which ultimately alter the landfall locations and frequencies. QTPSC affected the intensity and location of the subtropical high systems through the SC level, which in turn changed their track patterns, landfall locations and frequencies. Due to the blockage of the mainland of China, the ACE of TCs generated far (near) away from the mainland was on the high (low) side. Moreover, TCs with high ACE usually had curved track patterns and longer lifetimes, while TCs with low ACE had flat track patterns and shorter lifetimes. Additionally, ACE was associated with interannual variations of TC generation locations and track patterns.