A comparative study of ELF and VLF noise characteristics of nor’wester at a low latitude tropical station

Two pre-monsoon thunderstorms (nor’westers) in the Gangetic West Bengal have been considered to study the effect of source activity and wave propagation at a low latitude station. Lightning discharges, due to cumulonimbus cloud, propagate in the form of electromagnetic radiation have received in the form of sferics by sensitive receiver in ELF and VLF bands simultaneously. Local meteorological observatory recorded the wind speed of April 1, 2018 as 85 km/h blowing from the northwesterly direction while that for April 17, 2018 as 98 km/h blowing from the same direction. In addition to wind speed other meteorological parameters, viz. temperature, humidity and pressure have also been taken into account with a view to find the source activity. Kolkata Doppler Weather Radar observations showing the squall line and cloud top height during the peak activity of the storms have also been analyzed for the two occasions. We have made the spectral recordings of sferics round-the-clock during the disturbed weather caused by the pre-monsoon thunderstorms. The results obtained from the multi-technique observations are interpreted and discussed.