Identification of melting snow using data from dual-frequency microwave links

Using data from a dual-frequency microwave link it is possible to identify periods of transmission affected by melting snow. This is because, in melting snow, the relation between attenuation and the amount of precipitation is nonlinear and depends on the frequency in a way that differs from the dependence in rain. This implies that the ratio of the single-frequency estimates of apparent rainfall rates will be different in melting snow from those obtained in rain. This forms the basis of an algorithm that is shown to work well for a 23-km dual-frequency (12.8 GHz/17.6 GHz) link near Bolton in north west England and for a 29-km dual-frequency (10.5 GHz/17.5 GHz) link near Essen in Germany. The effectiveness of the algorithm is judged by noting the recorded temperatures in those minutes identified by the algorithm as being affected by melting snow