Since 1969, the Bell System has been conducting continuous rain attenuation experiments on earth-satellite paths. The experiments were carried out at four New Jersey sites by the radio basic research group of the Crawford Hill Laboratory, and at three Georgia sites, two Illinois sites, and two Colorado sites by the radio system engineering group of the Holmdel Laboratory. The measurement frequencies include 11.7, 13.6, 15.5, 17.8, 19, and 28.5 GHz. Interim results of the 10-year (1969–1978) experiments have been published in various technical journals and conference proceedings. For the convenience of system engineers, this paper summarizes the new results and the previously published results and discusses the implications of these data to the design of satellite radio communication systems. The summary includes the geographic dependence, the frequency dependence, the diurnal, monthly, and yearly variations of rain attenuation statistics, the diversity improvement factors, the fade duration distributions, the dynamic rain attenuation behavior, the long-term (20 years) rain rate distribution for U.S. locations, and a simple empirical model for rain attenuation.

Rain attenuation on earth-satellite paths — summary of 10-year experiments and studies

Two methods are described to obtain long-term (≥20 years) distributions of 5-minute point rain rates from data published by the National Climatic Center for U.S. locations. A set of simple empirical formulas for converting the distribution of 5-minute rain rates into rain attenuation distributions on 11-GHz radio paths has been deduced from data measured in Georgia. Additional data measured in several other locations also support this empirical formulation. These simple formulas and 5-minute point rain rate distributions are useful for path engineering of 11-GHz radio. The work on rain rate distributions discussed in the paper derives from approaches suggested by the late W. Y. S. Chen.5,9,16

11-GHz radio: Nationwide long-term rain rate statistics and empirical calculation of 11-GHz microwave rain attenuation

A new methodology is described for estimating the 5-minute rain rate distribution from yearly 5-minute maximum rain rate data and yearly accumulated rainfall data published by the National Climatic Center for U.S. locations. The method previously described gives the high rain rate portion of the distribution, whereas the extended methodology yields the complete distribution, which is assumed to be approximately lognormal. The three parameters characterizing the lognormal distribution can be calculated by application of the theory of extreme value statistics. The calculated results agree well with the 20-year data. The accuracy of the calculated results is limited by the instability of extreme rain rate data with a finite time base. Two-year rain rate data measured by a tipping bucket rain gauge at Palmetto, Georgia, are used to demonstrate that the time variation of rainfall process obeys a proportionate relationship, supporting the lognormal hypothesis.

Mere on rain rate distributions and extreme value statistics

The extinction cross-section of single particles of dimensions comparable with the wavelength has been measured using a double resonance technique at 100 GHz. Results agree well with Mie's theory. The technique is applicable to moving particles with velocities up to a few metres per second.

Measurement of extinction cross-section of single particles at 100 GHz

Measurements have been made simultaneously of attenuation at 36 and 110 GHz caused by rain on a 220 m terrestrial path. The relationships between attenuation and rainfall rate and between the attenuations at each frequency have been compared with theory.

Attenuation/rain-rate relationships at 36 and 110 GHz

Observations for one year over a 2.65 km path have yielded distributions with time of the depth of fading, duration of fading and the time between fades, and information on the weather situations producing rain which gives high attenuation. Observed attenuation has also been related to rainfall rate at a point.

A.M. Zavody

Papers

Investigations of attenuation by rainfall at 110 GHz in south-east England