Fig. 18

An example of the events where sinusoidal TEC oscillations with large amplitude are observed under a moderately disturbed meteorological condition on April 25, 2014. The panel a shows the meteorological parameters and the panel b shows the TEC variation. The wind direction and speed are variable in the first half of the day (blue dashed circle), and a rapid variation of wind velocity starts around 10:00UT although the amplitude is not very large compared to the cases of tropical squall. Nearly monochromatic variations are encircled by red dashed circles