PPP, Fourier transform and spectrum width measurements of ARM scanning radars

Description

The first three radar Doppler moments (reflectivity, velocity, and spectrum width) are usually estimated from the Doppler spectrum that is obtained by Fourier transformation (FT) of the normalized autocorrelation function of the radar signals. The moments can also be calculated using the Pulse Pair Processing (PPP) method that uses the lagged 0 and lagged 1 autocorrelation functions. Recently, some researchers even use lagged 2 and lagged 3 autocorrelation functions to calculate the moments. Here, we are investigating the impact of the selected signal processing technique (FT or PPP) on the value and interpretation of the radar Doppler spectrum width, a parameter of great importance for retrieving microphysical and turbulence properties. For the PPP method, the scanning radar effective beam width is a function of the lagged time. It increases with lagged time increasing. Because effective beam width impacts spectrum width measurement, the shorter lagged time should be considered when designing new moment estimators. Using recorded I/Q time series from the scanning ARM cloud radars (SACRs), we will investigate the impact of the estimator (FT versus PPP) on the recorded radar Doppler spectrum width.