Spectral density of millimeter wave amplitude scintillations in an absorption region

Filho, F. Medeiros; Jayasuriya, D.; Cole, R.S.; Helmis, C. G.

doi:10.1109/tap.1983.1143111

Cited by 31 publications

(10 citation statements)

References 7 publications

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“…Given the complexity of this suburban site it is difficult to draw firm conclusions on this apparent effect of crosswind on bichromatic scintillometry at this stage. Given that the position of the spectrum is known to change with wind speed (Medeiros Filho et al, 1983;Nieveen et al, 1998;, and that C 2 n can be underestimated if the filter excludes part of the scintillation signal under very low wind speed conditions (Solignac et al, 2012), the suitability of the bandpass filter was also re-examined. However, the choice of filter frequency did not seem to explain the poor performance and modifying the filter frequencies did not resolve the issues.…”

Section: Temperature-humidity Correlationmentioning

confidence: 99%

Infrared and millimetre-wave scintillometry in the suburban environment – Part 1: Structure parameters

et al. 2015

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Abstract. Scintillometry, a form of ground-based remote sensing, provides the capability to estimate surface heat fluxes over scales of a few hundred metres to kilometres. Measurements are spatial averages, making this technique particularly valuable over areas with moderate heterogeneity such as mixed agricultural or urban environments. In this study, we present the structure parameters of temperature and humidity, which can be related to the sensible and latent heat fluxes through similarity theory, for a suburban area in the UK. The fluxes are provided in the second paper of this two-part series. A millimetre-wave scintillometer was combined with an infrared scintillometer along a 5.5 km path over northern Swindon. The pairing of these two wavelengths offers sensitivity to both temperature and humidity fluctuations, and the correlation between wavelengths is also used to retrieve the path-averaged temperature-humidity correlation. Comparison is made with structure parameters calculated from an eddy covariance station located close to the centre of the scintillometer path. The performance of the measurement techniques under different conditions is discussed. Similar behaviour is seen between the two data sets at sub-daily timescales. For the two summer-to-winter periods presented here, similar evolution is displayed across the seasons. A higher vegetation fraction within the scintillometer source area is consistent with the lower Bowen ratio observed (midday Bowen ratio < 1) compared with more built-up areas around the eddy covariance station. The energy partitioning is further explored in the companion paper.

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Section: Temperature-humidity Correlationmentioning

confidence: 99%

Infrared and millimetre-wave scintillometry in the suburban environment – Part 1: Structure parameters

et al. 2015

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“…• Only the real part of the refractive index fluctuations is considered here; the imaginary part corresponding to phase fluctuations caused by atmospheric absorption (e.g. by water vapour) has been ignored, see Medeiros Filho et al (1983) and Nieveen et al (1998) for details. • In Eq.…”

Section: Theorymentioning

confidence: 99%

“…Thus it is possible to make an estimate of v from the frequency spectrum-this is known as the fast Fourier transform technique (Poggio et al 2000). From the literature it appears there is no single agreed upon definition of the exact position of the corner (Clifford 1971;Medeiros Filho et al 1983;Wheelon 2006). In this study the corner frequency f c = v(λL) −1/2 is marked in Fig.…”

Section: Scenario 11: Constant Crosswind In Space and Timementioning

confidence: 99%

Effects of Non-Uniform Crosswind Fields on Scintillometry Measurements

Ward

Evans

Grimmond

2011

Boundary-Layer Meteorol

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The effects of a non-uniform wind field along the path of a scintillometer are investigated. Theoretical spectra are calculated for a range of scenarios where the crosswind varies in space or time and compared to the 'ideal' spectrum based on a constant uniform crosswind. It is verified that the refractive-index structure parameter relation with the scintillometer signal remains valid and invariant for both spatially and temporally-varying crosswinds. However, the spectral shape may change significantly preventing accurate estimation of the crosswind speed from the peak of the frequency spectrum and retrieval of the structure parameter from the plateau of the power spectrum. On comparison with experimental data, non-uniform crosswind conditions could be responsible for previously unexplained features sometimes seen in observed spectra. By accounting for the distribution of crosswind, theoretical spectra can be generated that closely replicate the observations, leading to a better understanding of the measurements. Spatial variability of wind speeds should be expected for paths other than those that are parallel to the surface and over flat, homogenous areas, whilst fluctuations in time are important for all sites.

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“…Here, . Similar to the analysis for the temporal spectral density of log amplitude scintillations carried out in reference [4], the phase spectral density functions in the low-and high-frequency regions are obtained as…”

Section: Introductionmentioning

confidence: 99%

“…That is, the theoretical temporal frequency of the phase fluctuations should display a 8/3 slope at both the low-and high-frequency regions of the spectrum, with a transition region in between. Results for the plane wave log-amplitude spectra have been presented elsewhere [4]. We note that in the high-frequency region, [5].…”

Section: Introductionmentioning

confidence: 99%

Analysis of asymptotic theory of differential phase millimeter-wave scintillations in the oxygen absorption region

Sarma

Cole

2003

IEEE Trans. Antennas Propagat.

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This paper presents a model for dual frequency differential phase scintillations for a plane wave propagating through a turbulent medium characterized by a complex refractive index. In contrast to the predicted enhancement of the low-frequency portion of the amplitude spectrum by absorption fluctuations, our theoretical model predicts that the absorption mechanism has virtually no significant effect on the absolute phase spectrum, but can enhance the differential phase spectrum at intermediate frequencies when the propagation frequencies are very close. The effect of turbulence scale size is also analyzed. Experimental differential phase spectra agree well with the theoretical models presented here.

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Spectral density of millimeter wave amplitude scintillations in an absorption region

Cited by 31 publications

References 7 publications

Infrared and millimetre-wave scintillometry in the suburban environment – Part 1: Structure parameters

Infrared and millimetre-wave scintillometry in the suburban environment – Part 1: Structure parameters

Effects of Non-Uniform Crosswind Fields on Scintillometry Measurements

Analysis of asymptotic theory of differential phase millimeter-wave scintillations in the oxygen absorption region

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