Dual-frequency links—a complement to gauges and radar for the measurement of rain

Rainfall measurement in urban areas can be hindered by a variety of difficulties affecting both raingauges and radar. Gauges can be very difficult to site as space is often at a premium, and radar is likely to be affected by clutter. In this paper, we consider the potential of dual-frequency microwave links to measure rainfall in urban locations. The difference in the attenuations experienced by a pair of links operating at well-chosen frequencies can be approximately linear with rain rate and relatively insensitive to unknown parameters such as the dropsize distribution. The method could therefore be used to provide estimates of path-averaged rainfall in locations where more traditional measuring instruments are unreliable. Results are presented for 12 months of data from a 14 km link operating in the Bolton area of north–west England. Rainfall estimates derived using the dual-frequency method are compared with those obtained from a local network of raingauges, and a nearby Met Office weather radar. The results suggest that dual-frequency microwave links can serve as useful complements to raingauges and radar, improving rainfall estimation, particularly in urban catchments.