The ionosphere plays a critical role in radio wave transmission, reflection, and scattering affecting communication, navigation and positioning systems directly. This study analyzes the disappearance of short-wave echoes during the extreme geomagnetic storm on 10-12 May 2024 using observations of digisondes and incoherent scatter radar(ISR) of the Chinese Meridian Project (CMP). The results show that the short-wave absorption over Chinese regions caused by X3.9 and X5.8 solar flares on 10-11 May 2024 lasted for a short time, with interruptions of digisonde short-wave signals at some stations such as MHT and YUZH stations were interrupted. During the main and recovery phases of the geomagnetic storm, the strong ionospheric negative storm reduced electron density, decreased the critical frequency of the ionospheric F-layer, and raised its peak height, resulting in incomplete or vanished ionogram echoes over a long period, as well as distorted or missing automatic calibration results. Observations from the Sanya ISR of CMP reveal vertical ionospheric drifts at low latitudes on 10-11 May and a strong negative storm on 11-12 May driven by prompt penetration electric fields(PPEF) and disturbance dynamo electric fields (DDEFs), which are consistent with the storm-time ionograms. In conclusion, the long-duration backscatter echo failures in ionograms during geomagnetic superstorm is caused by short-wave interruption induced by the strong ionospheric negative storm and vertical uplift of the ionosphere. This study improves the understanding of ionospheric storm effects on digital ionosonde observations and provide a priori knowledge for improving the quality control of ionosonde observational data and automatic feature extraction during space weather disturbances.
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