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Wave Characteristics
What Happens Before We See a Breaking Wave at the Beach?
Waves approaching the Texas Coast are, in general, wind-generated.
All water waves, no matter how large or small, have a few fundamental characteristics in common. The following is a diagram of a wave traveling through the water before it starts to break as it approaches the nearshore.
The sinusoidal, or snake like, pattern of a wave is the signature of all waves. The surface of the ocean or a lake that an observer sees is the net result of all the different waves that are traveling through the water at any given moment. The sea or large water body surface is a composite of all the different waves. Thus, the sea surface is the result of a series of sinusoidal wave patterns all with different wave lengths and wave heights. The complex wave we observe is made up of all the simple waves added together.
Waves interfere or travel through each other and when doing so they may add to each other's height or they may cancel each other out. Constructuve interference is when two waves add together making one wave that is bigger. Destructive interference is when two waves cancel each other out, making a smaller wave than each individual wave.
Wave Related Definitions
Fully Developed Sea - a given wind speed can only generate waves of a certain size. In other words, after a period of time, the waves can get no bigger. The waves are described as fully formed and are the largest waves that can be created for a given wind speed. Once formed, this swell travels indefinitely, altered only by friction with the bottom or obstacles, such as islands or continents.
Wave - A disturbance caused by the movement of energy from some source through some medium. The disturbance can sometimes be viewed as a "hump" in the medium. The traveling "hump" produces the appearance of movement that we see as a wave.
Water Wave - A disturbance caused by the movement of energy due to wind forcing, volcanic activity or earthquake through water.
Wave crest - The highest part of a wave.
Wave frequency - the wave frequency is defined as the number of waves passing a fixed point in a given amount of time. If we take a stopwatch, count the number of waves that pass a fixed point over a 30-second interval and divide by 30 then you have the wave frequency. Wave frequency is important to ocean engineers and architects who construct jetties, piers, and other anthropogenic? objects in or near the ocean.
Wave trough - The lowest part of a wave.
Wave height - vertical distance between the trough and the crest of a wave.
Wavelength - horizontal distance between the successive crests of a wave.
Wave period - time interval between the passage of successive crests at a stationary point. For example, if you stand on the end of a pier, start your stopwatch when a wave hits a fixed spot, and stop your stopwatch when the next wave hits that point, you will have measured the wave period. The wave period can provide important clues about surf conditions. Long-period waves tend to be larger and stronger, while short-period waves are smaller and less energetic. Surfers measure the period of waves to get an idea of the swell to follow within the next several hours. Generally, longer period waves contain travel longer distances, have more energy, and create higher breakers on the shore.
Wave base - maximum depth to which waves move the water; equals about half of the wave length.
Wave Trains - The generation of waves from the time the wind starts blowing to the time that fully-developed seas are achived yeilds a series of waves with different wave periods and speeds. Since the longer period waves tend to be faster, these waves move out ahead of the rest of the waves. This is how groups of wave trains develop. A wave train is a group of waves traveling at the same speed across the ocean. These waves, obviously, hit the beach at the same time and, hence, create the well-known phenomenon of wave sets.
Wave Speed - The speed of a wave is simply how far it moves in a given amount of time. There is a close relationship between wavelength and speed. Small waves tend to move slowly at a few knots (1 knot equals 1 nautical mile per hour). Medium-size waves may move at tens of knots; large waves move 30 - 50 knots and more. Tsunamis, which are the largest waves of all, can reach speeds up to 450 knots.
Links to Wave Research
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