Effect of thunderstorm on microwave line-of-sight propagation
TL;DR: In this paper, the behavior of microwave signal propagation during such storms has been studied, utilizing a terrestrial microwave line-of-sight link, and it is characterized by an increase in signal level with deep fluctuations.
Abstract: Thunderstorms frequently occur during the months of April and May over Calcutta. The behavior of microwave signal propagation during such storms has been studied, utilizing a terrestrial microwave line-of-sight link. Storm period is characterized by an increase in signal level with deep fluctuations.
Citations
More filters
TL;DR: In this paper, amplitude scintillations in an 11.5 GHz SIRIO-Earth link have been evaluated by means of scintillation index, and hourly values of this index have been compared to the ground temperature measured in a site close to the vertical projection of the path.
Abstract: Analysis of amplitude scintillations in an 11.5 GHz SIRIO-Earth link has been performed. The intensity of scintillations has been evaluated for July 1984 by means of scintillation index. The hourly values of this index have been compared to the ground temperature measured in a site close to the vertical projection of the path. Both scintillation index and temperature seem to follow a similar cyclical behaviour. The relationship between the number of occurrences and the value of the index is also represented, together with a two-segment linear-wise approximation.
51 citations
01 Oct 1985
TL;DR: In this article, a method for estimating theoretical scintillation power is outlined, which may lead to more accurate estimates of turbulence parameters, and examples of power spectra obtained during calm summer nights, clear sky noons and in presence of clouds are shown.
Abstract: Amplitude scintillations in a low elevation link from SIRIO satellite are discussed. Examples of power spectra obtained during calm summer nights, clear sky noons and in presence of clouds are shown. Selected noon spectra have been compared to radiosoundigs and known model of turbulence has been found appropriate to describe the spectra, if some simple assumptions are made. A method for estimating theoretical scintillation power is outlined which may lead to more accurate estimates of turbulence parameters.
2 citations
10 Jul 1989
References
More filters
TL;DR: In this paper, the proper interpretation of irregular motions in the upper atmosphere has been investigated by a variety of techniques, but their proper interpretation has yet to be established. But their proper meaning has not yet been established.
Abstract: Irregularities and irregular motions in the upper atmosphere have been detected and studied by a variety of techniques during recent years, but their proper interpretation has yet to be established...
1,886 citations
TL;DR: In this paper, a wave-like corrugation of the ground of wavelength 2π/k, small enough for the earth's rotation to be neglected, was obtained for streamline, dry, isentropic, inviscid flow in which the disturbance is only a small proportion of the wind velocity.
Abstract: The disturbance in an air current, whose velocity may vary with height, caused by irregularities in the ground, is obtained. For a wave-like corrugation of the ground of wavelength 2π/k, small enough for the earth's rotation to be neglected, the stream function of the disturbance satisfies Ψ″ – (g/c2 +β) Ψ + (gβ/U2 – U″/U – k2) Ψ = 0(12)
Some circumstances in which waves may have large amplitude only in the lower layers of the atmosphere are described. In order that such waves may occur over level ground in the lee of mountains the parameter l must normally decrease upwards, where l2 = gβ/U2 – U″/U (13)
With two layers, the lower of depth h, these waves can occur if l12 – l22 > π2/4h2 (17)
Fourier's integral theorem is used to obtain the flow in two instances. Fig. 3 shows the wave due to a single long ridge in a stream in which the wind is stronger at higher levels. Fig. 5 shows the flow of a shallow current descending from a plateau, the air being calm above.
Nodal surfaces, as in Fig. 5, occur only when the depth of the layer exceeds a critical value, depending on the details of wind speed and temperature.
The well-known cloud phenomena associated with the waves are briefly described in section 6, and in section 7 the effect of isolated mountains rather than long ridges is considered.
The theory is only valid for streamline, dry, isentropic, inviscid. flow in which the disturbance is only a small proportion of the wind velocity.
521 citations
TL;DR: In this paper, theoretical researches on the problem of the disturbance of an atmospheric current flowing over a mountain range, carried on during the last ten years, prove that most of the characteristic characteristics of the atmospheric current are present.
Abstract: The theoretical researches on the problem of the disturbance of an atmospheric current flowing over a mountain range, carried on during the last ten years, prove that most of the characteristic obs...
380 citations
TL;DR: In this paper, a simplified method of scaling scintillation index is described, and the accuracy of the simplified method is determined by a comparison with measurements of SCI by machine computation.
117 citations
TL;DR: In this paper, a general formulation for temporal frequency spectra of the fluctuations of plane, spherical, and beam waves operating at two frequencies is given based on weak turbulence and frozen-in assumptions.
Abstract: General formulations for temporal frequency spectra of the fluctuations of plane, spherical, and beam waves operating at two frequencies are given based on weak turbulence and frozen-in assumptions. The cross spectra and the coherence are obtained for the amplitude at two frequencies, the phase at two frequencies, and the amplitude at one frequency and the phase at another frequency. The results are examined in detail for plane and spherical waves. For the spectrum of the index of refraction \kappa^{-n} in the inertial subrange, the amplitude spectrum behaves as k^{(5-n)/2} for \omega \rightarrow 0 and k^{2}\omega^{1-n} for \omega \rightarrow \infty . The phase spectrum for \omega\rightarrow 0 and for \omega\rightarrow\infty behaves as k^{2}\omega^{1-n} with different constants. These results agree well with the experimental work of Janes et al. [11] at 9.6 and 34.5 GHz, and explains the ratio of the spectra at two frequencies. Also noted is the experimental slope of -2.6 as and for \omega \rightarrow \infty which may be compared with 1-n = -2.66 using the Kolmogorov spectrum of n = 11/3 . The amplitude and phase coherence are calculated, and the results agree well with the experimental data. This agreement is indicative of the general validity of the theory for frequencies as low as 10\sim30 GHz and the path length as long as 60 km. It is also shown that using the preceding theory, the wind velocity and the structure constant C_{n} can be deduced from the experimental data. Theoretical wind velocity of 15.6 knots obtained from the propagation data compares favorably with the meteorologically measured value of 14 knots, and two values of C_{n} obtained independently from the amplitude and phase measurements closely agree with each other.
102 citations