Effects of tropical cyclones in the ionosphere from data of sounding by GPS signals

The problems of recording the ionospheric response to tropical cyclones (TCs) and the possibilities for detecting such a response using GPS (Global Positioning System) signals are discussed. Investigations of ionospheric effects of tropical cyclones with the use of different geophysical methods and technologies of GPS application for remote diagnostics of the ionosphere are reviewed. The results of investigating the action of tropical cyclones on the Earth’s ionosphere on the basis of measurements of variations in the total electron content at the global network of ground-based double-frequency GPS receivers are presented. It is shown that (a) the recording of tropospheric effects in the ionosphere is associated with the difficulties of detecting weak disturbances and their identification against the general background of variations and with the problems of identification of sources of such disturbances; (b) geomagnetic storms mask the effects of tropospheric disturbances in the upper ionosphere; and (c) when identifying the ionospheric effects of tropical cyclones, one must pay the bulk of attention to the search for the enhancement of the intensity of disturbances in ionospheric parameter variations.