The effect of HF radar beam patterns on surface current and wind direction measurements

Phased array HF radars are widely used for mapping surface currents and wind directions at high resolution in time and space. The beam is formed using simple physical optics principles that produce sidelobes. Several authors have alluded to errors produced in the measurements by sea echo energy in the sidelobes. Here we simulate the effect of sidelobes in surface current and wind direction measurements, both in smooth conditions and when the field has abrupt shears. The effects of sidelobes on these first-order measurements are small, even with short antenna arrays. We find no justification for adopting weighted windows on the array to reduce sidelobes at the expense of narrow beam width.