Sea clutter power spectral lineshape measurements

This paper presents measurements of unusual sea clutter made at low grazing angles using a multi-band pulsed radar (MBPR) on the English coast at Sennen Cove, Land's End in Cornwall. The trial site was chosen because of the wide range of weather conditions encountered there in the winter months. The distribution of raw radar cross section (RCS) returns and that of the variation in Doppler power spectral density (PSD) are presented in the examples discussed. This paper focuses on the Doppler returns from the sea. These returns exhibit large RCS at unusual Doppler velocities as well as the usual time varying component of the spectral shape. The large RCS returns are attributed to sea water plumes being 'whipped' off the sea, becoming airborne and accelerating to the wind velocity. This type of return, recorded at wind speeds as low as 20 knots provides a mechanism for heterogeneous Doppler clutter returns at offsets larger than would be predicted by the usually quoted spectra for radar returns in a sea environment.