The triple frequency space can be used to compare radar observations and scattering models. Three frequencies can be compared in 2 dimensional space using a combination of two Dual Wavelength Ratio (DWR) i.e. the difference of the logarithmic effective reflectivity factor from two frequencies. Triple frequency space contains rich information since the position of snowflakes in this framework depends on snow particle structure, bulk snowfall density, and characteristic size of the PSD.
Until now, studies were unable to relate the observed scattering properties from radars to particle shape. This limitation is overcome in this studies by combining radar observations with in-situ measurement of snowflakes at the ground. Three cases collected during the recent Finland reveal previously published triple frequency signatures such as a bending-away in the triple frequency from the curve of classical spheroid scattering models in the presence of large (>5 mm) snow aggregates. This study also reveals new signatures for rimed particles which appear along an almost horizontal line in the triple frequency space.
Kneifel S., A. V. Lerber, J. Tiira, D. Moisseev, P. Kollias, J. Leinonen, (2015) Observed Relations between Snowfall Microphysics and Triple-frequency Radar Measurements. Accepted to the Journal of Geophysical Research