Monitoring of Inland Waters by Dual-Frequency Precipitation Radar: First Results

Permanent monitoring of inland waters in cold regions with long-time snow and ice covers is very important for the population safety. Modern spaceborne radars can significantly extend the capabilities of the terrestrial hydrological network, since they enable one to perform measurements over large areas. In 2014, the Japan Aerospace Exploration Agency (JAXA) launched the spaceborne dual-frequency precipitation radar (DPR). The main objective of the mission is the precipitation measurement. However, the radar cross section (RCS) measured at the maximal range contains information about the scattering surface. For the first time, DPR measurements over the Russian territory were processed. The sources of in situ data were hydrological stations. The Gorky reservoir and the Volga River were selected for sensing small-area inland waters. The data processing confirmed the possibility of detecting inland waters whose area is significantly smaller than the radar footprint. A ground-to-water ratio was introduced to estimate the open water area inside the footprint. Processing of the DPR data obtained for the Lake Baikal enabled us to calculate the dependence of the RCS on the incidence angle and propose a novel algorithm for separating open water and ice cover. The Moksha River was selected as a wetland with many small rivers. The data processing has shown that the spring change of inland waters and soil can be observed in the DPR image.