Multitechnique studies of nor'wester using electrical and meteorological parameters
Radar observations of nor'wester (premonsoon thunderstorm) as experienced over the Gangetic West Bengal and the integrated field intensity of atmospherics (IFIA) at 10, 20 and 30 kHz recorded over the tropical station at Calcutta have been analysed. The records of IFIA reveal that, during n...
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
1994-01-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/12/232/1994/angeo-12-232-1994.pdf |
| Summary: | Radar observations of nor'wester (premonsoon
thunderstorm) as experienced over the Gangetic West Bengal and the integrated
field intensity of atmospherics (IFIA) at 10, 20 and 30 kHz recorded over the
tropical station at Calcutta have been analysed. The records of IFIA reveal
that, during nor'wester, the enhancement in the signal level occurs in three
different stages: (i) gradual rise of atmospherics (GRA), (ii) first sudden
enhancement of atmospherics (SEA<sub>1</sub>) and (iii) second sudden
enhancement of atmospherics (SEA<sub>2</sub>). Their respective occurrences have
been found to be prevalent in pre-noon, latenoon and afternoon hours of a day.
Of the three stages, GRA and SEA<sub>1</sub> have been found to occur before the
onset of thunderstorm, while SEA<sub>2</sub> may even occur after its onset. A
comparative study reveals that the precipitation during premonsoon thunderstorms
is associated with the second sudden enhancement, while it is associated with
the steady recovery of IFIA during the monsoon and postmonsoon thunderstorms.
The characteristics of the first nor'wester of every year have been critically
examined with an additional consideration of simultaneous radiosonde records. A
probable explanation has been made in terms of the distribution of the effective
sources at such times around the observing site. |
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| ISSN: | 0992-7689 1432-0576 |