Abstract:
Narrow Bipolar Pulses (NBP) of a single
thunderstorm from a coastal location in Sri Lanka were
subjected to S-transformation in order to study their timefrequency information. This study is an extension to a similar
study carried out by the authors where properties of NBPs were
analyzed using the wavelet transformation. Keeping in line with
the previous study, 18 events pertaining to equal number of
positive and negative NBPs with the narrowest temporal widths
were studied. The data was obtained from the southern coastal
area of Sri Lanka (Matara - 5.950 N, 8.530 E) from a highly active
thunderstorm, which occurred during the month of May in 2013.
The waveforms were recorded with a 10 ns resolution within a
100 ms time window. The spanning (width) and the ratio of peak
power amongst the initial and overshoot pulses were measured
and compared for each polarity. The negative NBPs had an
average spanning of 134 - 371 kHz. The overshoot of the same
had an average range of 127 - 255 kHz. The positive NBPs had an
average spanning of 103 - 245 kHz. The overshoot of the same
had an average range of 102 - 195 kHz. The ratio of peak power
of NBPs to overshoot had an average of 1.08 for both positive and
negative pulses. The spectrogram reveals the initial and
overshoots pulses to be relatively equal in power intensities.
