Sea backscatter, spikes and wave group observations at low grazing angles

Analysis of low grazing angle sea backscatter data has resulted in new information on the characteristics of backscatter, spikes and wave group processes. The data were collected at Joint US/UK experiments by coherent, polarimetric shore-based X-band radars at coastal loch and ocean channel locations with grazing angles at the sea surface in the vicinity of 6 degrees. At low grazing angles HH backscatter produces spiky amplitude characteristics and higher observed Doppler, compared to VV. The VV backscatter, which is dominated by lower Doppler Bragg backscatter, also contains some spike returns which usually display significantly different time profile and lower intensity than the corresponding HH return. The fixed antenna mode used for data collection provides for direct observation of wave group processes and parameters from which the characteristics of the dominant surface wave can be derived. The fixed antenna data sets can be directly processed via two-dimensional FFTs to provide k-ω plots displaying the gravity, wind waves and wave group processes observed by the radar