Analysis of rain clutter data from a frequency agile radar

Measurements of rain clutter were taken with a frequency agile S band radar for the purpose of studying the Doppler power spectra and the variation of backscattered power with space, time, and frequency. The clutter was found to be nonhomogeneously distributed in both space and time, but the mean backscattered power versus frequency relation seemed to involve only a single parameter having a spatial and temporal variation. Although the radar was looking into the surface wind, a significant portion of the backscattered signal energy was always found to lie in the negative frequency range, and the Doppler power spectra were sometimes found to have multiple peaks at both positive and negative Doppler frequencies. The simplest explanation for such spectra is that of a wind shear operating on a vertically stratified distribution of clutter, and assuming this to be the case, it can be estimated that the wind shear was of the order of 8 m s^−-1 km^−-1 and that the peaks were produced by horizontal bands or clumps of clutter whose vertical extent was of the order of 200 m.