Quantitative precipitation estimations from operational polarimetric radars for hydrological applications

Precipitation is the primary input to rainfall-runoff models. Meteorological radars have the potential to provide estimates of precipitation at high spatial and temporal resolution. This distributed information can be used in turn to improve our understanding of the hydrological processes of the natural system. This paper describes ongoing research with the C-band radar in Trappes, south-west of Paris, France, based on a two years polarimetric dataset to provide more accurate estimates of precipitation in an operational environment. Following Gourley et al (2006), preliminary work is undertaken to remove the biases and noises of the basic polarimetric variables (Z, Z_DR, &Phi_DP, &rho_HV). Special emphasis is directed towards issues related to the implementation of dual-polarisation into operations. This includes the analysis of data collected at low, potentially shielded, elevation angles, discussion of the impact of the radome and the assessment of the impact of the antenna rotation rate on the quality of dual-polarisation variables. Next, the performance of two Z-R relationships for rain-rate retrieval (Testud et al (1999), Thompson (2006)) is evaluated and discussed. This work is carried out in the context of risk management.