Echo and capability analysis of 94 GHz cloud radars

The echo characteristics and capability of the 94 GHz cloud radars of England are analysed by refering to the Galileo radar, 35 GHz radar, raindrop disdrometer, rain gauge and sounding data. The results show that (1) 94 GHz cloud radars can observe cloud structures of the clouds and weak precipitations, small scale variations in the clouds and fogs, and the positive and negative Doppler velocity of fogs; (2) the significant echo characteristics that distinguish 94 GHz cloud radars from centimeter wave radars are that the decrease of the radar reflectivity factor at the bottom of bright bands is slight or not and the dim bands which generally are of 600 m width exist above the bright bands, which are caused by non-Rayleigh scattering of bigger rainfall or ice crystal with the maximum size of aggregates able to be more than 3 mm in dim bands and even more than 6.8 mm in some dim bands, and the significant increase of Doppler velocity and spectral width implying the top of melting layer; (3) compared with 35 GHz radars, 94 GHz cloud radars may underestimate the top height of high clouds and the reflectivity factor of 94 GHz cloud radars is weaker than that of 35 GHz radars due to the signals attenuation and non-Rayleigh scattering of 94 GHz cloud radars, but 94 GHz cloud radars can filter the ground clutter and detect low clouds. The results can provide a reference for reliability analysis of 94 GHz cloud radar echoes in China. Combining with the other detection methods, 94 GHz cloud radars can reveal physical mechanism for all kinds of weather, which are of important significance in researches on weather forecast, investigation into cloud physics, weather modification and climate change.