Ionospheric response to the effects of tropical cyclone (TC) “Mahasen” in 2013 and Hudhud in 2014 is studied on the equatorial ionosphere over the Indian sector for the first time using Global Positioning System‐derived total electron content (TEC) data. We observed an anomalous decrease of 3.8 TEC unit (1 TECU = 1016 el m−2) in vertical TEC (VTEC) value from the monthly mean for TC Mahasen and 2.1 TECU for TC Hudhud on the day of the landfall. We have also observed similar VTEC depletion of 1.5, 1.9, and 2.1 TECU for three different receivers on the landfall day for TC Vongfong over Japan. This anomalous decrease is observed over a wide zone around the trajectory of the cyclone during the active cyclonic storm stage. This observed anomaly might be the result of combined effect of TC‐inspired gravity waves, ejection of neutral particles from the terminator of a TC, and lightning electric fields which redistribute the chemical constituents of the ionosphere by increasing the number of neutral particles at different ionospheric heights, thus decreasing the TEC over the satellite‐receiver path.

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The lightning climatology over Nepal is analysed in detail for the first time. For the analysis, we utilised the satellite-based lightning imaging sensor data for the period from 1998 to 2013. A comparison of these climatological results is also performed with two ground-based lightning detection networks, namely, the World Wide Lightning Location Network and the Global Lightning Network for 3 yr from 2011 to 2013. On analysing the data obtained from the three sources, we conclude that the months of April and May are extremely vulnerable in the perspective of lightning hazards in Nepal, in contrast to the results reported previously which indicated that the maximum lightning activity occurred in the month of June. The central and eastern regions of the country receive the majority of lightning strikes during the months of April and May. The present finding is supported by the thunderstorm frequency data obtained from the disaster Information Management System, Nepal and also from thunder-day data from NOAA.

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