Ionospheric Effects from the Super-Powerful Atmospheric Phenomena of September–October 2018 over the People's Republic of China: Results from Oblique Sounding

The study is concerned with the influence, which the action of the Super Typhoon Kong-Rey exerted on the ionosphere over the People's Republic of China (PRC). The coherent multiple path multifrequency software defined radio system of the Harbin Engineering University, PRC, has taken measurements. The typhoon event started on September 29, 2018 and ended on October 6, 2018. The reaction of the ionosphere to the action of the super typhoon was established to happen when the propagation path midpoints were 2,800–3,300 km from the typhoon while its energy attained a maximum (on October 1–2, 2018) and when the midpoints were 1,000-1,500 km from the typhoon while its energy decreased by a factor of about 4 on October 5–6, 2018. In the ionosphere, the effects were more obvious at the midpoints of the propagation paths closest to the typhoon, whereas effects were not observed at midpoints at the farthest range from the typhoon. The action of the typhoon on the ionosphere resulted in causing or enhancing by a factor of 2–3 quasi-sinusoidal changes in the Doppler shift, as well as in producing appreciable changes in the amplitude of the signals. In a few cases, the Doppler spectra exhibited broadening. The wave disturbances showed variability in the period range of ∼20 min to ∼120 min. From these measurements, we have inferred that the disturbances in the density of electrons were due to atmospheric gravity waves (AGWs) launched by the typhoon; furthermore, the greater the Doppler shift, the greater the AGW period. A decrease in the period from 120 min to 20 min was associated with a decrease in the Doppler shift amplitudes from 0.5-1 Hz to ∼0.1 Hz. Within the same range of periods, the amplitude of quasi-sinusoidal changes in the electron density decreased from a 6 to 0.4 per cent. The Doppler observations indicated that the typhoon and dusk terminator acted in concert to enhance the response of the ionosphere.