First observations of triple-frequency radar Doppler spectra in snowfall: Interpretation and applications

The potential of multifrequency Doppler spectra to constrain precipitation microphysics has so far only been exploited for dual-frequency spectra in rain. In this study, we extend the dual-frequency concept to triple-frequency Doppler radar spectra obtained during a snowfall event which included rimed and unrimed snow aggregates. A large selection of spectra obtained from low-turbulence regions within the cloud reveals distinctly different signatures of the derived dual spectral ratios. Due to the third frequency, a characteristic curve can be derived which is almost independent of the underlying particle size distribution and velocity-size relation. This approach provides new opportunities for validating existing and future snow scattering models and reveals how the information content of triple-frequency radar data sets can be further exploited for snowfall studies.