Advances in polarimetric X-band weather radar

In recent years, the deployment of X-band weather radars for dedicated applications such as gap-filling radars in complex terrain is considered by radar meteorologists and hydrologists. However, X-band weather radar observations suffer from the significantly higher attenuation in rain compared to the S- or C-band radar observations used operationally by the meteorological services. One way to deal with the attenuation is the use of radar polarimetry. This allows to measure the differential phase, i.e. the phase difference between the co-polarised radar echoes at horizontal and vertical polarisation. In the case of non-Rayleigh scattering, which at X-band already occurs at moderate rainfall rates, the differential phase is the superposition of a propagation and a backward-scattering component. Recently, we demonstrated that the differential phase can be decomposed in its propagation and backward-scattering component, leading to two weather radar observables that are independent of the radar calibration and the attenuation. In this contribution we show that once decomposed, the differential phase can be applied for microphysical retrieval in rain. We illustrate this technique with simulated weather radar data based on data from TU Delft's polarimetric X-band radar IDRA, [1].