LAUSR

Coherent microwave radar can provide reasonable wave heights, while wave periods are always overestimated. The “group-line” in the wavenumber–frequency spectrum is a possible mechanism to interpret the overestimation, but the previous model cannot fully explain it. To address the issue, a new model integrating with the breaking and its evolution is proposed for microwave composite sea surface scattering. The upwind-grazing Doppler characteristics for coherent microwave radar under VV polarization are analyzed. The model is validated by comparing the results between the simulation and the radar observation. It explains the creation of “group-lines” in the wavenumber–frequency spectra and indicates that the short waves generated after breaking and their evolution should be the dominant reason for the overestimation of wave period using coherent microwave radar. The result can provide a theoretical basis for improving the performance of wave measurements with coherent microwave radar and for microwave ocean remote sensing.