PROFILER SPECTRAL MOMENTS (WHAT IS MEASURES)

PROFILER SPECTRAL MOMENTS (WHAT IT MEASURES)

MOMENT	COMMENTS
Doppler Power Spectrum	Similar to the 89-D. However, it is possible to see peaks in the power spectrum due to clear air Bragg scattering and particulate Rayleigh scattering at the same time.
Signal Power	Measure of the amount of power returned to the profiler. Note that profilers are often not well calibrated, so it is not possible to derive a reflectivity value (Z) from S. Here is a schematic example.
Radial Velocity	Is the first moment (mean) of the Doppler power spectrum. One must be careful since the radial velocity may be due to clear-air data (Bragg Scattering) and/or precipitation (Rayleigh Scattering). Here is an example showing a Doppler power spectrum with precip and clear-air return. Vertical velocity is obtained from the vertically pointing beam. The sign convention is that positive is downward.
Velocity Variance	Interpreted in a similar manner as Doppler radar variance. It's a measure of turbulence, and can also be used to distinguish between different precip types.