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The differential phase ([[PHI].sub.DP]) measured by polarimetric radars is recognized to be a very good indicator of the path integrated by rain. Moreover, if a linear relationship is assumed between the specific differential phase ([K.sub.DP]) and the specific attenuation ([A.sub.H]) and specific differential attenuation ([A.sub.DP]), then attenuation can easily be corrected. The coefficients of proportionality, [[gamma].sub.H] and [[gamma].sub.DP], are, however, known to be dependent in rain upon drop temperature, drop shapes, drop size distribution, and the presence of large drops causing Mie scattering. In this paper, the authors extensively apply a physically based method, often referred to as the 'Smyth and Illingworth constraint,' which uses the constraint that the value of the differential reflectivity [Z.sub.DR] on the far side of the storm should be low to retrieve the [[gamma].sub.DP] coefficient. More than 30 convective episodes observed by the French operational C-band polarimetric Trappes radar during two summers (2005 and 2006) are used to document the variability of [[gamma].sub.DP] with respect to the intrinsic three-dimensional characteristics of the attenuating cells. The Smyth and Illingworth constraint could be applied to only 20% of all attenuated rays of the 2-yr dataset so it cannot be considered the unique solution for attenuation correction in an operational setting but is useful for characterizing the properties of the strongly attenuating cells. The range of variation of [[gamma].sub.DP] is shown to be extremely large, with minimal, maximal, and mean values being, respectively, equal to 0.01, 0.11, and 0.025 [dB[degrees].sup.-1]. Coefficient [[gamma].sub.DP] appears to be almost linearly correlated with the horizontal reflectivity ([Z.sub.H]), differential reflectivity ([Z.sub.DR]), and specific differential phase ([K.sub.DP]) and correlation coefficient ([[rho].sub.HV]) of the attenuating cells. The temperature effect is negligible with respect to that of the microphysical properties of the attenuating cells. Unusually large values of [[gamma].sub.DP], above 0.06 [dB[degrees].sup.-1], often referred to as 'hot spots,' are reported for 15%--a nonnegligible figure--of the rays presenting a significant total differential phase shift ([DELTA][phi].sub.DP] > 30[degrees]). The corresponding strongly attenuating cells are shown to have extremely high [Z.sub.DR] (above 4 dB) and [Z.sub.H] (above 55 dBZ), very low [[rho].sub.HV] (below 0.94), and high [K.sub.DP] (above 4[degrees] [km.sup.-1]). Analysis of 4 yr of observed raindrop spectra does not reproduce such low values of [[rho].sub.HV], suggesting that (wet) ice is likely to be present in the precipitation medium and responsible for the attenuation and high phase shifts. Furthermore, if melting ice is responsible for the high phase shifts, this suggests that [K.sub.DP] may not be uniquely related to rainfall rate but can result from the presence of wet ice. This hypothesis is supported by the analysis of the vertical profiles of horizontal reflectivity and the values of conventional probability of hail indexes. DOI: 10.1175/2009JAMC2039.1

The recent deployment of an innovative triple pulse rise time (PRT) scheme within the French operational radar network allows for the simultaneous collection of reflectivity and radial velocity measurements up to a range of 250 km with no ambiguity. This achievement brings new perspectives in terms of operational exploitation of Doppler measurements including the capability to consistently perform multiple-Doppler wind synthesis in a fully operational framework. Using real and simulated Doppler observations, the authors show that the 3D wind fields retrieved in that framework can definitely be relied upon to achieve a consistent and detailed mapping of the airflow structure in various precipitation regimes despite radar baselines averaging ~180 km and very limited scanning strategies. This achievement could be easily transposed to other operational networks and represents a remarkable opportunity to add further value to operational Doppler velocity measurements.

A polarimetric method is devised to correct for attenuation effects at C band on reflectivity [Z.sub.H] and differential reflectivity [Z.sub.DR] measurements. An operational cross-correlation analysis is used to derive advection vectors and to displace echoes over a 5-min time step. These advected echoes are then compared with observations valid at the same time. The method assumes that the mean change in the intrinsic [Z.sub.H] and ZDR over a 5-min period when considering 1-2 h of observations over the entire radar umbrella is approximately zero. Correction coefficients are retrieved through the minimization of a cost function that links observed decreases in [Z.sub.H] and [Z.sub.DR] due to attenuation effects with increases in differential phase shift ([[PHI].sub.DP]). The retrieved coefficients are consistent with published values for the typical ranges of temperatures and drop sizes encountered at midlatitudes, even when Mie scattering effects are present. Measurements of [Z.sub.H] and [Z.sub.DR] corrected using retrieved coefficients are compared with raw measurements and to measurements adjusted by mean coefficients found in the literature. The empirical retrieval method shows improvement over using mean correction coefficients based on comparisons of [Z.sub.H] from neighboring, unattenuated radars, disdrometer measurements, and analysis of [Z.sub.H] and [Z.sub.DR] as a function of [[PHI].sub.DP].