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What Forces Drive Wave Formation?

As one would anticipate, wind generated waves rely on the wind for energy. But what causes the wind to blow in the first place? The wind is the result of an "imbalance" in air pressure. This imbalance occurs as air is heated and rises. It will continue to rise until it reaches an elevation where the surrounding air has the same density (or pressure). If it cools, it will sink, again, until the surrounding air has the same density (or pressure).

Air rises and sinks because of changes in density that occur due to changes in air temperature. The simplest way to think of it is as the number of air molecules in a given volume (like the amount of air in an empty 2-liter Surge Soda bottle). As you add heat to the air, the air expands, and now we have fewer air molecules in the same volume, In other words, its density decreases. The opposite happens when you cool air. Colder air is more dense than warmer air.

Increases in density also bring about increases in air pressure; decreases in density cause air pressure to be lower. When there is a difference in air pressure, the air will move and continue to move until air pressure is the same everywhere. This moving air is known as wind.

What Makes the Wind to Blow on a Global Scale? On a global scale, areas of high pressure and low pressure across our planet are generated by the sun heating the equator more than the poles. This results in differential heating of the planet. Cold dense air descends from the poles, warm light air rises from the equator resulting in three convection cells in each hemisphere. The creation of high pressure cells and low pressure cells from differential heating of the planet produce the winds that drive wave formation.

On a more local scale, winds due to sea breezes that are observed during hot summer days occur due to the unequal heating rates of land and water. During the day, the land surface heats up faster than the water surface. Therefore, the air above the land is warmer than the air above the ocean. The warmer air rises because it is lighter than cooler air. Thus as the warmer air over the land surface rises the cooler air over the ocean flows over the land surface to replace the rising warm air.

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