Self-consistent measurements of differential phase and differential reflectivity in rain

The addition of polarisation capabilities to meteorological radars has considerably increased their potential applications. However, such radars still require careful calibration of absolute power to achieve their full potential. This paper describes a technique which utilises a combination of differential reflectivity and differential phase measurements in rain to achieve a self-consistent calibration. The method is illustrated using data obtained with the 3 GHz Chilbolton radar, which is capable of measuring five parameters: reflectivity, differential reflectivity, linear depolarisation ratio, Doppler velocity and differential phase. The ability of the calibrated radar to measure rain fall rates is demonstrated by comparison with rain gauge and distrometer data, while accurate microwave attenuation estimates are shown with reference to comparisons with 12 GHz and 20 GHz beacon measurements made with the Olympus communications satellite