源自南海东北部海区热带气旋的若干统计特征

1949－1998年50a中，源自南海东北部海区的热带气旋共67个，其中有17a无热带气旋产生，45a无台风。该海区产生的热带气旋及其有关的统计特征与南海南部和热带西太平洋的热带气旋不同：平均个数是厄尔尼诺年较反厄尔尼诺年少；春季型的厄尔尼诺过程中热带气旋生成较多；1970－1990的的强厄尔尼诺过程中热带气旋个数当年较次年多，1990年后则相反，与历次厄尔尼诺过程比较，1997－1998年特强厄尔尼诺过程中的热带气旋生成较多、发展较快、其异常的气候特征为有史以来所罕见。

SOME STATISTICAL FEATURES OF TROPICAL CYCLONES ORIGINATING FROM NORTHEAST SOUTH CHINA SEA

Sixty-seven tropical cyclones were observed over the northeast South China Sea (SCS) during 1949-1998. There were 17 years without tropical cyclones and 45 years without typhoons during the period. The statistical features of tropical cyclones are different from those generated over the southern SCS and the tropical West Pacific. On average, tropical cyclones have been generated less in El Nino years than in La Nia o nes, and in the El Nino events of autumn style than in those of spring style. Tropical cyclones occurred more in the first year than in the second year of El Nino events during 1970-1990, and contrary after 1990. In comparison with the historical El Nio events, the anomalous climate features of the tropical cyclones during the 1997/1998 strongest El Nio course, such as more quantity and faster development, have not been found in the records.