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Interpretation of radar observations of clouds employing millimetre waves may be confused by the presence of super-large drops in clouds. In the Letter, the effect of these drops on cloud attenuation (dB) and reflectivity (dBZ) is assessed, and the implications for radar system design discussed.

The authors present a method aiming to remove the smoothing effect due to the antenna beamwidth in the reconstruction of the rain reflectivity based on radar measurements. The function to be reconstructed is the spatial distribution Z(x, y, h) of the radar reflectivity Z of the precipitation, which is shown to be related by a Fredholm integral equation to the power received by the radar. This integral equation is transformed into a set of linear equations and subsequently solved through a constrained-linear-inversion technique. The method is then applied to the cases of both stratiform and convective rain, leading to an improved estimation of the reflectivity-peak location and intensity, and of the overall reflectivity profile.

Statistics of radar reflectivity are presented as a function of height. The data were derived from 3-dimensional maps of radar reflectivity obtained with a 10 cm radar on the 25 m diameter aerial at Chilbolton in southern England. The way in which reflectivity varies with height is of considerable importance to those assessing possible interference between earth-to-satellite links and terrestrial links. The present results show some differences from the CCIR model now used for such planning purposes.

An explanation is given for the peak sensitivity around 9?11 GHz to drop-size distribution and temperature of microwave attenuation due to a rain-filled medium. The sensitivity of radar reflectivity, differential radar reflectivity and differential radar cross-section to drop-size and temperature are also given. It is shown that at frequencies in excess of about 25 GHz the vertical radar cross-section of water drops can be greater than the horizontal.