Abstract: The local typhoon refers to the tropical cyclone formed in the South China Sea. 1949-2014 CMA-STI compiled "best track dataset for tropical cyclone" was chosen in this study, the local typhoon intensity and intensity change characteristics on the scope of the study area (5°-22.5°N, 105°-120.5°E) were discussed. The results showed as follows: (1) The time curves of local typhoon intensity were similar to symmetric funnel-shape, that was changed from weak-strong-weak, intensity change was the most significant before and after 6 h in maximum intensity, and intensity change in summer was quickly than in winter. (2)The local typhoons had one intensified centers, located in the east of Hainan Island coastal area, but which decreased obviously near the south China coastal land area; further analysis showed that the typhoon intensified/weakened area moved with the changing seasons, in the summer it was mainly in the north offshore/nearshore area near 18°-23° N, while in the winter it was close to the west offshore/nearshore area near 10°-18° N, and the average decreased rate in winter was bigger than that in summer. (3) Furthermore, the eastward local typhoon intensity was generally stronger than that of westward, average intensity of summer eastward typhoon was the largest and that of winter westward typhoon intensity was the least; around the maximum intensity, the summer eastward typhoon intensity change was the fastest and winter westward typhoon was the slowest. Summer westward typhoon intensity distribution was stronger in the north, and eastward typhoon intensity distribution formed a northeast belt-shaped. In winter, westward and eastward typhoon intensity distribution was stronger in west. The difference of such spatial distribution was mainly due to the typhoon moving paths with the seasons. (4)The duration time of maritime activity with the intensity and variation in the range was proportional. The shorter maritime activity, the more westward paths, the average intensity was weaker, intensified/weakened centers was much smaller, intensified/weakened rate was slower; conversely, the longer maritime activity, the more eastward paths, the intensity distribution had multicenter, its average intensity was stronger, intensified/weakened center was more concentrated and broad, intensified/weakened rate was faster.

Key words: typhoon, intensity, intensity change, the South China Sea