Evolution of short wind-waves over uniform surface currents
Résumé
Experiments were conducted on the large IMST Facility to better specify the effect of uniform surface current on the evolution of the short wind waves, mostly involved in microwave backscattering. An adverse current induces a decrease of the dominant wave frequency, a large increase of the significant wave height, a broadening of wave angular dispersion, a lengthening of the dominant wavelength and an increase of the effective fetch length. A following current has the opposite effects. Moreover, an adverse current acts as a low-pass frequency filter inducing a blockage of the short wind waves and generating explosive sub-harmonic instabilities. Finally, scatterometer radar returns are found to be affected by the currents more particularly at low wind speed.
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