Jin Wu 
Following the sudden slope rise, the present data seem to 
show three stages of development : gradual change, rapid change, 
and approaching, saturation, as marked successively in figure 9 by 
three segments of lines, The rapid change begins when waves start 
to break occasionally and ends when wave breaking was observed at 
most wave crests. Cox's data display only two stages of development. 
The shorter wind fetch and the lower turbulence level are believed to 
be the reasons for causing the general shift of Cox's results. The 
wave regime in Cox's tank may not have passed the occasional brea- 
king stage; wave breaking was not reported by Cox. 
IV.3 Features of slope-distribution curves 
The slope-distribution curves, shown in figure 7, are ske- 
wed toward the down-wind direction at medium wind velocities. The 
skewness disappears at high wind velocities and peakedness follows. 
The skewnesses of slope distributions, a measure of the asymmetry 
of wind-generated water waves, are shown in figure 10a. 
In order to understand the skewness features, an experiment 
was done by placing the wave-height gauge 3 mm transversely from 
the telescope focal spot at the water-surface. The outputs of the op- 
tical instrument, set in the vertical plane, were recorded simultane- 
ously with those of the wave height gauge. The location of the light 
pulse relative to the wave-height profile, shown on the records, cor- 
responds physically to the relative position of the capillary waves 
distributed along the basic wave profile. 
The distribution of the capillary waves on the down-wind 
and up-wind faces of the basic wave profile is plotted in figure 10b. 
At medium velocity, the pulses (wavelets) at the down-wind face ve- 
ry much outnumber those at the up-wind face. This is the velocity 
range at which the maximum skewness of the surface-slope distribu- 
tion occurs. As the wind velocity increases, the pulses (wavelets) 
become more and more evenly distributed over the up-wind and 
down-wind faces, and the slope-distribution curve thus becomes less 
and less skewed. 
The distribution of wavelets along basic wave profiles, pre- 
sented in figure 10b, is also interesting in two other ways. This dis- 
tribution indicates the presence of one of the equilibrium regimes, 
the formation of parasitic capillaries in the front face of the basic 
wave profile. This distribution may cause different backscattering 
of electromagnetic waves from the leeward (down-wind) and from 
the windward (up-wind) faces of the basic wave profile. 
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