A circulation change related to stratospheric sudden warming was investigated to examine the role of the stratosphere in equatorial tropospheric convective activity. A composite analysis of twelve stratospheric warmings from 1979 to 2001 revealed that the meridional circulation change associated with stratospheric warming in the polar region produces a lower temperature in the equatorial lower stratosphere and upper troposphere, which leads to a seesaw of convective activity in the troposphere -- an enhancement of convective activity near the equatorial southern hemisphere (10¿S-equator) but a suppression in the tropics of the northern hemisphere (5¿N--15¿N).