The transfer of heat and water vapor from the ocean to the air above it
depends on a disequilibrium at the interface of the water and the air. Within
about a millimeter of the water, air temperature is close to that of the surface water, and the air is nearly saturated with water vapor.
But the differences, however small, are crucial, and the disequilibrium is
maintained by air near the surface mixing with air higher up, which is
typically appreciably cooler and lower in water-vapor content. The air is mixed
by means of turbulence that depends on the wind for its energy. As wind speed
increases, so does turbulence, and thus the rate of heat and moisture transfer.
Detailed understanding of this phenomenon awaits further study. An interacting—and
complicating—phenomenon is wind-to-water transfer of momentum that occurs when
waves are formed. When the wind makes waves, it transfers important amounts of
energy—energy that is therefore not available to provide turbulence.
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