Comparative analysis of TEC disturbances above regions of tropical cyclones in the north-west Pacific Ocean

We studied ionospheric total electron content (TEC) disturbances associated with tropical cyclones (TCs). The study was based on the statistical analysis of six cyclones with different intensity which occurred in the North-West Pacific Ocean in September-November 2005. We used TEC data from the international network of two-frequency ground-based GPS receivers and NCEP/NCAR Reanalysis meteorological archive. TEC variations of different period ranges (2-20 and 20-60 min) are shown to be more intense during TC peaks under quiet geomagnetic conditions. The highest TEC variation amplitudes are registered when the wind speed in the cyclone and the TC area are maximum. The intensification of TEC disturbances is more pronounced when several cyclones occur simultaneously. We found that the ionospheric response to TC can be observed only after the cyclone has reached typhoon intensity. The ionospheric response is more pronounced at low satellite elevation angles.