Radar coherent scatter from precipitation: Part II

The mechanism just discussed in the first part of this presentation is illustrated here in both rain and snow. An analysis of time series of the magnitude of the amplitudes (A) reveals statistically significant periodic components which can only be associated with coherent scatter. Thus,the detection of coherent scatter from precipitation does not require a Doppler radar. Furthermore, it is possible to estimate the coherent scatter contribution to the total power with an incoherent radar. However,in order to gain further insights into the characterization of the gratings, Doppler radar observations are required. To see this, the time series of amplitudes is separated into a coherent scatter and incoherent scatter components. The Doppler spectrum of the coherent scatter component reveals peaks that are consistent with the peak frequencies responsible for the oscillations in A and that can be associated with unique integer multiples of the half-wavelength as to be expected from Bragg scatter gratings. Wavelet analysis reveals details about the structure of these transient gratings. Finally, as a result of this work the standard relations in common use between Doppler velocity variance and decorrelation time are not valid when coherent scatter is present.