Polarimetric Azimuthal Spectral Histogram Exposes Types of Mixed Scatterers and the Cause for Unexpected Polarimetric Averages

Echoes detected by polarimetric weather radar in clear air contain signals from air and biological scatterers. Discriminating the various scatterer types from a composite echo is challenging due to variability in scatterres´ quantity, azimuthal dependences of their polarimetric properties, and uneven mixing in resolution volumes. We use polarimetric spectral densities to estimate the volume content by constructing two dimensional (2D) histograms. The dimensions used to form image are Doppler velocity and polarimetric variable. The assimilation of these histograms in azimuth results in a 3D-azimuthal-spectral-histogram (3DASH). This representation allows us to use transparency for small occurrences to visualize the 3D-signatures of dominant content. The scatterer types have distinguishable signatures in 3DASH due to their diverse physical shapes, scattering properties, different headings, and speeds. 3DASH can help to understand what constitutes the polarimetric averages of the resolution volume. 3DASH can help provide resources for establishing intrinsic polarimetric values/functions for different types of biological scatterers, which are necessary for scatterer classification algorithms.