Ionospheric disturbances observed from a single GPS station in Hong Kong during the passage of Super Typhoon Hato in 2017

Abstract

The powerful convection in the lower atmosphere, for example, tropical cyclones (TCs), has a high probability of causing ionospheric disturbances. We observed evident ionospheric disturbances during the passage of Super Typhoon Hato in 2017 by analyzing the highest elevation vertical total electron content (HeVTEC) time series, that is, the VTEC from the Global Positioning System (GPS) satellite with the highest elevation at each epoch, retrieved from a single GPS station in Hong Kong. The results demonstrate that the daily maximum of HeVTEC time series on each day during the TC period experienced a large fluctuation ranging from 33.5 TEC unit (TECU) to the peak value 62.0 TECU. The peak value 62.0 TECU occurred on the TC landfall day 23 August 2017, approximately twice as high as that of non-TC-impacted days. We also found that the TEC spatial gradients above the landfall area increased by around 50% and 200% in the north-to-south and west-to-east directions, respectively. We also examined the daily mean bias (MB) of VTEC above Hong Kong with respect to the mean VTEC during the past 27 days from 20 July to 15 August in 2017. The largest VTEC MB was observed in the west of the landfall area along the TC moving direction, on the TC landfall day. Our findings provided the evidence that the Hato's landfall over the coast near Hong Kong caused the apparent ionospheric disturbances above the landfall area.