East Asia and Western Pacific METEOROLOGY AND CLIMATE

405
The results shown In Fig. 1 are for the open sea, with the data
illustrating that the proposed formulae can be applied to very high wind
velocities up to 50 or 60 m s~
(Wu 1980, 1982). We have also provided
modifications due to air-sea temperature differences; see Fig. 2, where
C
is the wind-stress coefficient obtained under unstable (or stable)
conditions, Z is the anemometer height, and L is the Monin-Obukhov
stability length (Papadiraitrakis et al. 1987). Such a figure, of
course, is familiar to you for results over land; but this is over the
sea surface. 2.0
Sable Conditions:
CJ/C10«*xpf0.70Z/U
}— C,/C10 » exp 1-0.95 2/U
Figure 2.
Variations of Wind-Stress Coefficient with Stability
Length. The shaded areas cover the range of variation of
results from various investigations. This is reproduced
from ttu (1986).
Speaking about the sea surface, we have to deal with waves. A
parameter, the so—called wave age, is used; it can be expressed in one
of two ways, either as the ratio between the phase velocity of dominant
ocean waves and the wind velocity c/ u i/y or with the wind-friction
velocity c/u^. For the open sea where dominant ocean waves propagate
in pace with the wind, the ratio C/U IQ has a value of nearly unity.
The corresponding value for c/u^ is about 25. At short fetches near
shore or fronts, the dominant waves are shorter and have a smaller