Estimating Spectral Differential Phase and Spectral Specific Differential Phase to Retrieve Particle Population Separated Ice Water Content Profiles

Within the ice phase of clouds the interaction between ice crystals and /or of ice crystals with super-cooled liquid water leads to an enhanced growth of the ice particles. The growth of ice particles is an important process for precipitation formation in the mid-latitudes. Nowadays such interaction processes are still not clearly understood. To examine the ice particle growth within raining cloud systems polarimetric radar measurements, such as differential reflectivity, Z_DR, differential phase, ψ_DP, and specific differential phase, K_DP, are used to analyse and understand changes in the ice particle microphysics.

Using moments of polarimetric radar measurements is a common way to improve rain estimation, hydrometeor classifications and microphysical process understanding. Nevertheless, spectral resolved radar data have shown to improve the analysis and understanding of cloud microphysical processes. Therefore, the spectral polarimetric measurement capabilities of the Transportable Atmospheric RAdar (TARA), a FMCW S-Band radar profiler, are used to estimate ψ_DP and K_DP in the spectral domain. The new parameters are termed, sψ_DP and sK_DP. The spectral domain allows to relate and/or separate contributions of different particle populations (e.g pristine crystals and aggregates) in the signal. Furthermore, the spectral domain also offers the possibility to retrieve quantitative microphysical information related to ice particles.

In this work we will explain the estimation of spectral differential phase and spectral specific differential phase and show some first results based on real radar data. The new parameter, sK_DP,is used to improve the Ice Water Content (IWC) retrievals. The objective is to obtain separate IWC profiles of pristine particles and aggregates.