Surface current measurements by HF radar over fresh water at Lake Michigan and Lake Tahoe

HF radar is widely used over salt water to measure surface currents, winds and waves. The authors report results over fresh water in Lakes Michigan and Tahoe. Although these pilot experiments were brief, they established that useful HF radar observations of surface currents can be obtained out to ranges of about 10 to 15 km with wave heights corresponding to wind speeds of about 3 to 7 m/s. Ranges 2 to 3 times larger and often more would be expected over salt water due to improved ground wave propagation. The currents measured by HF radar closely tracked in-situ current measurements by an acoustic Doppler current profiler. These encouraging results demonstrate the utility of HF radar in freshwater applications, but with significantly less spatial coverage than over salt water.