Gravity waves are the product of Joule heating, the auroral electrojet during geomagnetic substorms, the equatorial electrojet in the thermosphere, severe thunderstorms, tornadoes, and hurricances in the troposphere, etc. A thorough understanding of sources and sinks of gravity waves can greatly advance our knowledge concerning atmosphere-ionosphere-magnetosphere couplings. We have limited ourselves in this paper to discussions of couplings between the ionosphere and the troposphere during the time periods of isolated tornadoes on the stormy day of November 20, 1973. Identification of the location of wave sources for waves detected at F region ionospheric heights was attempted by using the observed characteristics of wave propagation in ray-tracing computations. Computed locations of wave sources were then compared with conventional meteorological data. The results show that the sources of the gravity waves associated with tornadoes were always on the squall lines and near the tornado touchdown locations. The results also suggest that ionosphere-troposphere coupling studies can contribute to our understanding of the dynamical development of severe storms.