Gravity Waves and Ionospheric Irregularities over Tropical Convection Zones observed by GPS/MET Radio Occultation

GPS/MET observations of the tropical atmosphere of the southern hemisphere (5S to 25S) during February 1997 are analysed, 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 140W), Brazil (50W), Africa (40E), and Indonesia/Australia (110E).