A comparison of rain attenuation and drop size distributions measured in Chilbolton and Singapore

Abstract

[1] Attenuation of radio waves caused by precipitation, especially in the form of rain, is considered to be the limiting factor for new communication systems that will exploit the radio wave spectrum at frequencies higher than about 30 GHz. Over the last 40 years, much effort has gone into theoretical studies characterizing rain in terms of statistical drop size distributions (DSDs), the shapes and velocity dependence of raindrops, and the calculation of raindrop extinction cross sections. This paper focuses on specific data sets and data processing and different ways of viewing DSDs that may help in quantifying some of the important parameters in radio wave propagation from experimental data. Values for the coefficients k and a in the relationship for specific rain attenuation g = kR a are presented, together with rain-rate-dependent parameters for fits of DSDs to standard statistical distributions. These are based on data from Chilbolton, England, and from Singapore. The distributions measured at Chilbolton and Singapore are very different, which strongly suggests that drop size distributions differ under different climatic conditions. Comparisons are also presented of attenuations calculated with values of k and a determined from the DSDs and values found from logarithmic regression between simultaneous rain rate and attenuation measurements at 57, 97, 135, and 210 GHz at Chilbolton. This paper gives a strong indication that the International Telecommunication Union Radiocommunication Sector model for specific rain attenuation is inadequate at frequencies higher than about 70 GHz.

Variation of multimodality in rainfall drop size distribution with wind speeds and rain rates

“…McFarquhar [13] says that multimodal peaks are observed in computed models, but not systematically in physical data. Åsen and Gibbins [14] argue about the existence of multimodal peaks in observed rainfall, and say that the presence of multimodal peaks may be due to an error in the calibration of the bins. McFarquhar and List [15] recompute the bin boundaries based on the recalibration of the RD‐69 disdrometer done at the Laboratory of Atmospheric Physics at the Eidgenössische Technische Hochschule (ETH) in Zurich, Switzerland [14].…”

“…Åsen and Gibbins [14] argue about the existence of multimodal peaks in observed rainfall, and say that the presence of multimodal peaks may be due to an error in the calibration of the bins. McFarquhar and List [15] recompute the bin boundaries based on the recalibration of the RD‐69 disdrometer done at the Laboratory of Atmospheric Physics at the Eidgenössische Technische Hochschule (ETH) in Zurich, Switzerland [14]. However, Ekerete et al [16] showed that even with the ETH calibration there was still the presence of multimodality, and not just a consequence of the instrumental artefacts as it compared the Distromet ® (manufacturers of the disdrometer) calibration with the ETH's recalibration.…”

The Studies of Millimeter Waves at 60 GHz in Outdoor Environments for IMT Applications: A State of Art

“…For measuring the effect of rain of radio wave propagation especially at 60 GHz the studies are carried out by Walther et al [17] at two different sites namely UK and Singapore. They have obtained the data from the Rutherford Application Laboratory (RAL) located in southern part of England.…”

Rain attenuation prediction based on theoretical method with realistic drop shape for millimeter-wave radio in tropical region

“…Since DSD is idiosyncratic to the climate of a region, a single model may not be adequate to describe the physical reality of DSD in all region. Comparative studies [10] between several DSD models have shown that Log-normal models generally give the best fit to the measured DSD in tropical regions. Hence, in this work, the locally measured DSD in the form of Log-normal distribution presented in [11] is used…”