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Ann. Geophys., 25, 1253-1262, 2007
www.ann-geophys.net/25/1253/2007/
© European Geosciences Union 2007
A time-localized response of wave growth process under turbulent winds
Z. Ge1 and P. C. Liu2
1National Research Council, U.S. Environmental Protection Agency, 960 College Station Road, Athens, GA, 30605-2720, USA
2NOAA Great Lakes Environmental Research Laboratory, 2205 Commonwealth Blvd., Ann Arbor, MI, 48105, USA
Abstract. Very short time series (with lengths of approximately 40 s or 5~7
wave periods) of wind velocity fluctuations and wave elevation were
recorded simultaneously and investigated using the wavelet bispectral
analysis. Rapid changes in the wave and wind spectra were detected, which
were found to be intimately related to significant energy transfers through
transient quadratic wind-wave and wave-wave interactions. A possible pattern
of energy exchange between the wind and wave fields was further deduced. In
particular, the generation and variation of the strong wave-induced
perturbation velocity in the wind can be explained by the strengthening and
diminishing of the associated quadratic interactions, which cannot be
unveiled by linear theories. On small time scales, the wave-wave quadratic
interactions were as active and effective in transferring energy as the
wind-wave interactions. The results also showed that the wind turbulence was
occasionally effective in transferring energy between the wind and the wave
fields, so that the background turbulence in the wind cannot be completely
neglected. Although these effects are all possibly significant over short
times, the time-localized growth of the wave spectrum may not considerably
affect the long-term process of wave development.
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