Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Annales geophysicae 12 (1994), S. 232-239 
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 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 (SEA1) and (iii) second sudden enhancement of atmospherics (SEA2. 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 SEA1 have been found to occur before the onset of thunderstorm, while SEA2 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.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0992-7689
    Keywords: Meteorology and atmospheric dynamics ; Lightning ; Precipitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The records of VLF atmospherics over Calcutta and then over Kalyani (West Bengal) during the torrential rainfall, caused by violent monsoon and post-monsoon depressions, exhibit distinct long-period fadings both at day and night. Interesting results obtained from an analysis of round-the-clock atmospherics data and associated meteorological parameters are reported in this paper. A possible correlation between the severe meteorological activity with the solar geophysical phenomena was studied. The results are indicative of an interesting sequence of solar-terrestrial events. A tentative conclusion is reached, suggesting an origin of the fading from atmospheric gravity waves generated in the centre of activity of the depressions concerned.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Annales geophysicae 14 (1997), S. 1051-1059 
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Solar diffuse radiation data including global radiation, shortwave and longwave balances, net radiation and sunshine hours have been extensively analyzed to study the variation of diffuse radiation with turbidity and cloud discharges appearing in the form of atmospherics over the tropics. Results of surface radiation measurements at Calcutta, Poona, Delhi and Madras are presented together with some meteorological parameters. The monthly values of diffuse radiation and the monthly ratios of diffuse to global solar radiation have been examined, with a special emphasis in relation to the noise level of atmospherics at Calcutta in the very low frequency band. The results exhibit some definite seasonal changes which appear to be in close agreement with one another.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A comparative study is made of the stepped structure of atmospherics during sunrise and sunset hours at three harmonically related frequencies in the VLF band, observed at the coast of the Bay of Bengal. The occurrences of the steps, their duration, time sequence and amplitudes are critically examined. Our analysis reveals that the start times of the third and second steps of the sunrise effect are always before ground sunrise, while the start of the main step is distributed on both sides of it. During sunset hours, the onset time of the main step is before the local ground sunset, but for the second and third steps, the onset times are after that. The results are interpreted by considering the multi-hop propagation as well as the distributed noise sources surrounding the observing site.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 31 (1982), S. 263-268 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Gleichzeitige Beobachtungen der Feldstärke atmosphärischer Radiogeräusche in drei Frequenzen im VLF-Band von Oktober 1976 bis September 1978 sind zur Untersuchung des Frequenzspektrums der Atmospherics analysiert worden. Die Ergebnisse werden für verschiedene Monate und Jahreszeiten dargestellt und hinsichtlich der Quellenaktivität und der Ausbreitungswirkung interpretiert.
    Notes: Summary Simultaneous observations of the field strength of atmospheric radio noise at three harmonically related frequencies in the VLF band for a period of two years from October 1976 to September 1978 have been analyzed to explore the frequency spectrum of atmospherics. The results have been shown for different months and seasons of the year and interpreted in terms of source activity and propagation effect.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 31 (1982), S. 411-419 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Die Feldintensität der VLF-Atmospherics, die über Calcutta registriert wurde, zeigt gelegentlich einen charakteristischen Abfall in Verbindung mit Regen in den Monsun-Monaten. Auf den plötzlichen Abfall folgt eine Unterbrechung und darauf eine Wiederherstellung, so daß sich eine sägezahnartige Form in der Registrierkurve bildet. Das Vorkommen und die Größen des Abfalls überwiegen bei 20 kHz im VLF-Band. Am häufigsten kommt der Abfall um Mittag und um Mitternacht vor.
    Notes: Summary The field intensity of VLF-atmospherics recorded over the tropical station, Calcutta (22°34′N, 88°24′E) occasionally exhibit a characteristic fall in association with the ground rainfall during monsoon months. The sudden fall is followed by a pause and a subsequent recorvery thus forming a clipped saw-tooth like appearance. The occurrences and magnitudes of the fall are predominant at 20 kHz in the VLF-band. They mostly occur around local noon and midnight hours.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 32 (1983), S. 173-179 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Es werden Radarbeobachtungen von zwei in der Vor-Monsunzeit über West-Bengalen aufgetretenen Tornados und die an der tropischen Station Calcutta registrierte integrierte Feldstärke der Atmospherics (IFIA) bei 30 kHz analysiert. Die Registrierungen der IFIA zeigen eine auffallende Änderung im Niveau mit einem anfangs plötzlichen Anstieg und einem darauffolgenden deutlichen Abfall mit Wiederholungen dieser Art in beiden Fällen. Die Charakteristiken dieser Änderungen werden analysiert und besprochen. Die synoptischen Verhältnisse werden im Zusammenhang mit beiden Tornados kritisch untersucht. Die gewonnenen Ergebnisse werden aus der Kenntnis der elektrischen Aktivität erklärt.
    Notes: Summary Radar observations of two pre-monsoon tornadoes as experienced over the Gangetic West Bengal and the integrated field intensity of atmospherics (IFIA) at 30 kHz recorded over the tropical station, Calcutta, have been analysed. The records of IFIA exhibit a pronounced variation in the noise level showing first a sudden enhancement and then a distinct fall which is repetative in nature in both the cases. The characteristics of the variations are analysed and discussed. The synoptic situations in connection with both the tornadoes have also been critically studied. The results obtained are explained by considering the existing knowledge of electrical activity.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 29 (1980), S. 131-141 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Während der Monsun-, Premonsun- und Postmonsunzeiten über der tropischen Station Calcutta bei Gewittern auftretende Atmospherics zeigen einige typische Charakteristiken. In allen Fällen ist ein stufenweises Ansteigen (GRA) und ein gleichmäßiges Abklinge (SRA) der Atmospherics festgestellt worden. Zwischen diesen zwei Änderungen tritt eine plötzliche Steigerung der Atmospherics (SEA) auf, die manchmal aus zwei Komponenten SEA1 und SEA2 zusammengesetzt ist. Diese bei 10 und 20 kHz beobachteten Tatbstände der integrierten Feldintensität der Atmospherics (IFIA) wurden in ihrer Beziehung zu Monsun-, premonsunalen und postmonsunalen Gewittern kritisch untersucht. Die Ergebnisse zeigen, daß der Niederschlag während der Monsun- und postmonsunalen Gewitter mit dem gleichmäßigen Rückgang der IFIA verbunden ist, während er bei den premonsunalen Gewittern mit der zweiten plötzlichen Steigerung der Atmospherics in Verbindung steht. Diese Anomalien wurden mit Ladungstrennungen in Gewittern in Zusammenhang gebracht. Ferner wurden auch die Unterschiede der entsprechenden Amplituden bei 10 und 20 kHz bei den verschiedenen Variationen der IFIA kritisch untersucht.
    Notes: Summary Thunderstorm associated atmospherics during the monsoon, premonsoon and postmonsoon seasons over the tropical station Calcutta show some typical characteristics. In all the cases gradual rise of atmospherics (GRA) and steady recovery of atmospherics (SRA) have been found. In between the above two changes, there is the sudden enhancement of atmospherics (SEA) which is some times composed of two components SEA1 and SEA2. All the above facts of the integrated field intensity of atmospherics (IFIA) observed at 10 and 20 kHz have been critically examined here in relation to monsoon, premonsoon and postmonsoon thunderstorms. The results exhibit that the precipitation is associated with the steady recovery of IFIA during the monsoon and postmonsoon thunderstorms while that during premonsoon thunderstorms is associated with the second sudden enhancement. These anomalies have been interpreted in terms of charge separation within thunderclouds. Moreover, the difference of the respective amplitudes at 10 and 20 kHz of the different variations of IFIA have also been critically focussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Meteorology and atmospheric physics 30 (1981), S. 279-288 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Eine Untersuchung der auf der tropischen Station Kalkutta registrierten VLF-Atmospherics bei 10, 20 and 30 kHz zeigte eine stufenweise Abnahme bei Sonnenaufgang, wobei die ersten zwei Stufen vor Sonnenaufgang relativ schwach entwickelt sind, während die letzte bei Sonnenaufgang beobachtete Hauptstufe immer sehr klar sichtbar ist. Die Ergebnisse der Untersuchung zeigen, daß der Abfall in der Hauptstufe wie auch seine Ausdauer größer war als in den zwei anderen Stufen. Die mittlere Dauer der ersten, zweiten und der Hauptstufe betrug entsprechend 21, 31 und 54 Minuten. Die Größen des Abfalls sind frequenzabhängig und haben ihr Maximum bei 30 kHz. Sie sind während der Sommer- und Monsunmonate kleiner als im Winter. Die Ergebnisse werden mit Berucksichtigung der Quellenaktivität und der Natur der Ausbreitung interpretiert.
    Notes: Summary An analysis of the VLF atmospherics at 10, 20 and 30 kHz recorded over the tropical station Calcutta exhibits stepped-falls during sunrise of which the first two steps observed before ground sunrise are relatively weak while the last one called the main stepped-fall observed around ground sunrise is always clearly visible. Results show that the fall of the main-step as well as its duration are greater than those of the other two steps. The average duration for the third, second and main steps are respectively 21, 31 and 54 minutes. The magnitudes of the fall are frequency dependent, being maximum at 30 kHz. They have also been found to be less during the summer and monsoon months than in winter. The results have been interpreted by considering the source activity and the nature of propagation involved.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Springer
    International journal of infrared and millimeter waves 20 (1999), S. 699-724 
    ISSN: 1572-9559
    Keywords: Rain rate ; Attenuation ; Isotherm height ; Effective height ; Microwaves and Sub-millimetre waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The results on attenuation of the radio wave due to rain at frequencies lying in the centimetre, millimetre and submillimetre wave bands for different rain rates over three Indian tropical stations are presented in this paper. The study is possible due to the availability of the rainfall rates measured by rapid response rain gauges and rain height over these stations. The results on attenuation were deduced by taking both 0° C isotherm height and effective height. The Stutzman and Dishman model with γ -value of 0.033 which is found suitable for the estimation of rain attenuation over the Indian stations has been critically examined in comparison with the attenuations deduced from CCIR (presently known as ITU-R) method.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...