Some experimental results on bistatic scatter from rain

A bistatic scatter experiment was conducted on a 55.2-km scatter path in Japan, at a frequency of 6.72 GHz, continuously from August 1975 to September 1977. In this bistatic scatter experiment the forward scatter experiment and a direct path measurement were made simultaneously, and a scanning-beam experiment was performed during two rainfalls. Investigations were made on the relationship between the equivalent radar reflectivity factor
Z_{e}
for a 2.3-km common volume height above sea level and the surface rain rate
R
(mm/h) directly under the common volume, and the distribution of
Z_{e}
. The
Z_{e}-R
relationship was found to be
Z_{e} = 151.4 R^{1.45}
on an average for total data including all rain types. The distribution of
Z_{e}
can be approximated by the lognormal distribution for a rainy period. The directivity of scattering from an ensemble of raindrops was measured by scanning the beam from a horn antenna in the vertical plane. For practical purposes the directivity was found to be similar to that of an electric dipole.