【摘要】 <正> 西北太平洋的台风,绝大多数是在ITCZ上发展起来的(1)(2)(3)。ITCZ上的台风活动常在某一个时段同时或连续有几个台风出现,而另一时段则没有台风出现或台风出现很少;这种ITCZ上台风活动活跃和不活跃的现象,常常是交替出现的。 根据1970—79年6—11月西北太平洋235个台风统计,我们发现同其他台风几乎同时(在48小时以内)形成的台风,占台风总数的45.5％,而与其他台风在相隔5天以内相继形成的,又占30.2％,单独零散出现的台风,只占24.3％。这表明西北太平洋台风有显著的集中出现的倾向。更多还原

【Abstract】 From the stat ist ics on typhoon occurrence on NW Pacific during June Nov.for 1970-79, We found that there is an apparent tendency of typhoon occurrence in a concentrative form.Two cases of the multi-typhoon formation on ITCZ.are aralyzed In one case there were five typhoons forming successively in half a month, In another case there were three typhoons generating almost simultaneously. It is found that bothof them are connected with tne interaction of the c irculat ions of Southern and NorthernHemispheres.It is the cross-equatorial currents that induce the multi-typhoon format ion on the ITCZ. The outbreak of the strong cross-equatorial current resulted from the cold air surge in S H crosses the equator at about 100°E or 150°Eaccording to the position of the long wave trough and then turns to westerly current in tropical NW Pacific. In the first case during the 15days period there were three cold surges in S.H.which caused the equatorial westerlies to the south of the ITCZ to persist for a relatively long time;Typhoons generated one after another at the east end of the equatorial wester1ies where the low level convergence. was maximum the second case there wlrl several maximum centers in eqatoruial westerlies original ing from S.H. and from the Bay of Baengal. Typhoonss formed s imulteneouas ly at the east endof these centers where were also the region of maximum convergfemce.更多还原