Abstract
Meteorological activities in the troposphere would affect electron concentrations and distributions in the ionosphere, thereby exciting ionospheric disturbance. To explore the ionospheric anomalies during severe convective weather, the ionospheric phenomenon during the heavy rainfall in Sichuan Province on 9 July 2013 was analyzed based on GNSS data. The Total Electron Content (TEC) are evaluated by carrier phase smoothed pseudoranges. Then, the dTEC (detrend TEC) sequences are obtained by using the cubic smoothing spline. They show obvious N-shaped ionospheric disturbances and have propagation characteristics, with the maximum of 0.4 TECU. Frequency domain analysis using continuous wavelet transform (CWT) also reached similar conclusions—that there are obvious ionospheric disturbances with different frequencies and intensity. Based on the isotropic assumption and feature points method, the horizontal propagation velocity of the disturbances in the ionosphere is estimated to be approximately 150 m/s. Then, Sichuan Province is divided into 1° × 1° grids, and the disturbance trigger source is determined via the grid searching method to be the central of Sichuan Province. Finally, the mechanisms causing ionospheric disturbance are discussed. During the heavy rainfall, the strong convection may excite gravity waves (GWs), which are driven by terrain and background wind fields to propagate upwards to the ionosphere and release energy, causing ionospheric disturbances.
Highlights
The ionosphere is an important component of the geospace environment
When the positions of the GNSS stations and the satellites are determined, the points of intersection for the GNSS signal with the single ionosphere sphere are the Ionospheric Pierce Points (IPPs)
Ionospheric disturbances can be studied by calculating the trajectory of the IPPs over the research area and comparing the slant total electron content (STEC) variations in a period of time before and after the rainfall
Summary
Its abnormal disturbances will have important effects on radio technology, spacecrafts, space weather research, and disaster prediction, etc. Irregularities in ionospheric electron density are affected by solar activities and geomagnetic changes, and by meteorological activities in lower atmosphere, such as the troposphere [1,2]. Research has shown that severe weather such as heavy rainfalls, thunderstorms, typhoons, cold waves, tsunamis, tornadoes, etc. Studies on ionospheric disturbances during severe convective weather events are of great significance. In 1951, Beynon et al first suggested that the ionospheric E-layer is associated with meteorological activities in lower atmosphere [6]. Bauer found that the critical frequency f oF2 of ionospheric F2 layer turned to peak 1–3 h after the typhoon center landed on the coastline [7].
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