Monitoring rain rate with data from networks of microwave transmission links

Monitoring microwave attenuation (20 to 45 GHz) of directional transmission links is a method to derive rain rate at high time resolution and in near-real time. Raindrops falling through a propagation path of a microwave link attenuate the transmitted signal quasi linearly with rain rate, allowing the estimation of path-averaged rain intensity. These data are valuable for meteorology, hydrology, agriculture, flood control, and others. The application to entire networks of commercial links would be a cost-effective method to fill data gaps where precipitation-radar data are either distorted or missing, such as large cities, valleys in mountain areas and developing countries. We will review the feasibility of the method and report on activities for setting up a project in Switzerland.