GPS/MET observations of the tropical atmosphere of the southern hemisphere (5 ¿S to 25 ¿S) during February 1997 are analyzed, when a high amount of convective tropospheric water vapor is at these latitudes. Enhanced gravity wave activity of the lower stratosphere at h=22--28 km is associated to areas of increased tropospheric water vapor pressure at h=4--6 km, regarded as a measure of tropical convection. Sporadic E and other ionospheric irregularities (vertical scales less than 7 km) of the mesosphere/lower thermosphere are observed to be highly correlated to gravity wave activity in the lower stratosphere and to tropical convection zones. We find 4 areas of enhanced ionospheric irregularities and stratospheric wave activity over Pacific (around 140 ¿W), Brazil (50 ¿W), Africa (40 ¿E), and Indonesia/Australia (110 ¿E). ¿ 2001 American Geophysical Union