East Asia and Western Pacific METEOROLOGY AND CLIMATE

some of the problems, which are backed up by our physical understanding,
but have so far been ignored by the remote-sensing community. According
to the current understanding, the radar returns with W polarizations
should be associated with ripples, the returns should increase contl-
1/2
nuously with the wavenumber of ripples, following roughly k ' ; the
actual returns, however, reach a saturated level, not Increasing with
the wavenumber.
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On the other hand, the HH polarized results should be
associated with breaking waves, they surprisingly follow very well the
predicted trend.
In addition, we have studied the ripple structures
and turbulence characteristics, and expected that the radar returns
should be very much influenced by the stability condition.
The radar
returns are intensified under unstable conditions are suppressed under
stable conditions.
In other words, first we have to find AT, but we
have no means of measuring it remotely now. Finally, we have to deal
with sea-surface conditions.
Pictures taken during the space shuttle
mission indicate that under light winds, say 6 or 7 m s , the sea
surface is covered by natural slicks.
According to our studies of the
marine microlayer, the suppression of ripple structures should follow
the trend shown in Fig. 7, where E s (f) and E c (f) are signal densities
from slick and clean surfaces.
In any event, I hope that all these
have illustrated to you that the studies of microscale air-sea
interaction are important to the remote sensing which may be of interest
to you.
Surface-Waff Length, X (cm)
Figure 7 Summary of Available Slick Measurements with Microwave ^
" Sensors. The curves are fitted on the basis of wave-damping
measurements. This is reproduced from Wu (1989b).