Daily radiosonde observations made at Tromelin Island (15.53°S, 54.31°E) in the Southern Indian Ocean over 3-year period (December 1998-July 2002) are used to characterize the variability of gravity wave activity in the tropical lower stratosphere (18-25 km). Tromelin Island is a 1km2 sandy desert island (1.6-length and 0.7-km width) located in a convective region in particular in austral summer during the passage of tropical cyclones. A previous work (Chane-Ming et al., GRL 2002) determined some gravity-wave parameters during the passage of Cyclone Hudah from 11 March to 30 April, 2000. The present study uses the analysis procedure of Allen and Vincent (JGR, 1995) to derive wave parameters in relation to the convective activity (OLR, TRMM precipitation rate) for comparisons with those of Coco Islands (12°S, 97°E) detailed in Vincent and Alexander (JGR 2000). This contributes to the cooperative effort in producing climatologies of wave parameters in a global scale from radiosonde data.