Ionospheric Effects over the People’s Republic of China from the Super-Powerful Tropospheric Western Pacific Phenomenon of September–October 2018: Results from Oblique Sounding

Abstract. The paper deals with the effects that accompanied the Super Typhoon Kong-Rey action in the ionosphere over the People’s Republic of China (PRC). The observations were made using the Harbin Engineering University, PRC, multifrequency multiple path coherent software defined radio system. The typhoon began on September 29, 2018 and ceased to exist on October 6, 2018. The ionospheric response to the super typhoon action was clearly observed to occur both on October 1–2, 2018 (when the typhoon was 2,800–3,300 km from the propagation path midpoints and its energy gained a maximum value) and on October 5–6, 2018 when the typhoon was 1,000–1,500 km from the midpoints and its energy decreased by a factor of about 4. The ionospheric effects are more pronounced along the nearest propagation paths, whereas no effect was detected along the propagation path at the farthest distance from the typhoon. The super typhoon action on the ionosphere was accompanied by the generation or amplification of quasi-periodic variations in the Doppler shift by a factor of 2–3, as well as by noticeable variations in the signal amplitude. The Doppler spectra were observed to broaden in a number of cases. The period of wave perturbations exhibited variability in the ~20 min to ~120 min range, which suggests that the perturbations in the ionospheric electron density were caused by atmospheric gravity waves (AGWs) generated by the typhoon; in addition, the greater the AGW period, the greater the Doppler shift. As the period increased from 20 min to 120 min, the Doppler shift amplitudes increased from ~0.1 Hz to 0.5–1 Hz, whereas the amplitude of quasi-periodic variations in the electron density increased from a few to several tens of per cent within the same range of the AGW periods. The Doppler measurements have shown that the dusk terminator and super typhoon acted synergistically to amplify the ionospheric response to these sources of energy.