Fetch. No, it’s not what you’re thinking. We’re not about to throw a stick for Fido to retrieve. Instead, we’re about to take a trip over water.
Oceanographers use the term fetch to describe the distance over water that the wind blows. That might not seem to be important to someone in New Mexico, Nevada, or Burkina Faso, but for anyone on either a big body of water or its shore, the term has real meaning. The reason lies in the connection between wind and waves.
Most surface waves on bodies of water are wind driven. Acquiring energy from unequal heating of Earth’s surface that causes differences in air pressure, the winds carry that energy to whatever they encounter, such as surface water. As they travel over the water, the winds impart some of their energy to the water. The water becomes a medium for the energy transfer, and, in turn, conveys that energy. Essentially, the energy travels through the water, and as it does, the water rises and falls to make the crests and troughs of waves.
Now here’s were fetch comes to play. The farther in distance and length of time that winds blow over the water’s surface, the more energy they transfer to the water, creating bigger waves. Circling a storm that might be 300 miles in diameter, winds of a hurricane have a very long fetch, and they are also high-speed winds. So, hurricanes generate big waves.
Now look at the human analog. Brief encounters between people can generate some waves, but long exposures can disturb the medium to a great extent. We’re talking storm waves capable of destroying seemingly durable structures. Think about the effects of human fetch. Years of nagging build to resentment. Years of degrading build to depression and lack of confidence. The waves of human emotion might start because of gentle breezes, but persistent breezes, stronger continuous winds, and even gales can have devastating effects.
Would that we could, as the National Hurricane Center follows hurricanes, closely monitor these human winds and map them. We might be able to make predictions on the size of the waves and warn of their potentially destructive effects.
Oceanographers use the term fetch to describe the distance over water that the wind blows. That might not seem to be important to someone in New Mexico, Nevada, or Burkina Faso, but for anyone on either a big body of water or its shore, the term has real meaning. The reason lies in the connection between wind and waves.
Most surface waves on bodies of water are wind driven. Acquiring energy from unequal heating of Earth’s surface that causes differences in air pressure, the winds carry that energy to whatever they encounter, such as surface water. As they travel over the water, the winds impart some of their energy to the water. The water becomes a medium for the energy transfer, and, in turn, conveys that energy. Essentially, the energy travels through the water, and as it does, the water rises and falls to make the crests and troughs of waves.
Now here’s were fetch comes to play. The farther in distance and length of time that winds blow over the water’s surface, the more energy they transfer to the water, creating bigger waves. Circling a storm that might be 300 miles in diameter, winds of a hurricane have a very long fetch, and they are also high-speed winds. So, hurricanes generate big waves.
Now look at the human analog. Brief encounters between people can generate some waves, but long exposures can disturb the medium to a great extent. We’re talking storm waves capable of destroying seemingly durable structures. Think about the effects of human fetch. Years of nagging build to resentment. Years of degrading build to depression and lack of confidence. The waves of human emotion might start because of gentle breezes, but persistent breezes, stronger continuous winds, and even gales can have devastating effects.
Would that we could, as the National Hurricane Center follows hurricanes, closely monitor these human winds and map them. We might be able to make predictions on the size of the waves and warn of their potentially destructive effects.
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