Chapter 6
HIGH WIND SPEED REGIME
Under high wind speed conditions breaking waves disrupt the air-sea
interface producing a two-phase zone—air-bubbles in water and sea spray in
air. This mixed-phase environment changes the dynamics and
thermodynamics of air-sea interaction especially within tropical cyclones.
6.
HIGH WIND SPEED REGIME
Breaking waves intermittently disrupt the air-sea interface. With
increasing wind speed, the sharp interface between the air and water
disappears for longer intervals (Figure 6-1). Under extreme conditions of
very high wind speeds, the concept of the air-sea interface becomes
problematic: A two-phase environment with gradual transition from bubblefilled water to spray-filled air is formed.
The effects of bubbles and sea spray appear to be of crucial importance
for air-sea exchanges in tropical cyclones. These effects can also be
important for extratropical winter storms.
In Section 6.1 of this chapter, we consider air-bubbles in the near-surface
layer of the ocean. Effects of the bubbles produced by breaking surface
waves include the modification of upper ocean turbulence by a buoyant
surface layer, their contribution to air-sea gas exchange, and to the acoustic
and optical environments. Sea spray and marine aerosol generation is the
subject of Section 6.2. Section 6.3 discusses the issues of modeling air-sea
exchanges in high wind conditions. Section 6.4 intends to explain the
recently discovered phenomenon of the limiting state of the aerodynamic
roughness under hurricanes conditions.