An experimental study of the temporal statistics of radio signals scattered by rain

Robert W. Hubbard, Joseph A. Hull, G. D. Thayer, and Philip L. Rice

Abstract: A fixed-beam, bistatic CW experiment designed to measure the temporal statistics of the volume reflectivity produced by hydrometeors at several selected altitudes, scattering angles and at two frequencies (3. 6 and 7. 8 GHz) is described. Surface rain gauge data, local meteorological data, surveillance S-band radar and great-circle path propagation measurements are also made to describe the general weather and propagation con­ditions and to distinguish precipitation scatter signals from those caused by ducting and other non-hydrometeor scatter mechanisms. The results­to-date cover the time interval September 15, 1970, to January 31, 1971. The cumulative distribution of rainy minutes for which the path loss signal exceeds a given value above system sensitivity is presented for the several path geometries. These cumulative distributions of amplitude­time durations of hydrometeor scatter signals are compared with measured cumulative distribution of surface rain rate measurements obtained for the same time period. The surface rain rate statistics are compared with long-term excessive precipitation data available for the southeastern United States.

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