Fig. 2

High-pass filtered GPS-TEC data (V-TEC) observed at Phimai station (PHIM). After the strong rainfall presented in Fig. 1, short period TEC variations are observed. The color of the traces indicates the elevation angle of the GPS satellites, EL, i.e., green; 10 < EL < 20, blue; 20 < EL < 30, red; 30 < EL < 40, and black; 40 < EL. Note that the oscillations in low elevation angle are probably so-called "multi-pass" effect of GPS signal. The data with the elevation angle greater than 50 degrees are used for power spectral analysis to avoid the multi-pass effect