Lab 6.3 – Wave Dynamics

Fundamental concept: Calculate wavelength and wave speed from wave period
Estimated time to complete: 30 minutes
Data skills preparation: Lab 2.1 – Time series
Materials needed: calculator

Your objective for this activity is to use the OOI data to investigate the characteristics of the waves that were measured at the buoy during the bomb cyclone event. In the previous activity you looked at the height of the waves associated with the storm and here you will examine other characteristics including the wave period and wavelength. Then you will determine the speed that these waves travel across the ocean after they leave the storm area where they are generated.

Wave Height and Wave Period


 

Interpretation Questions:

  1. What are the maximum and minimum values of significant wave period?
  2. Do the largest and smallest values of wave period and wave height happen at the same time?
  3. Compare the changes in wave height and wave period over time and determine if, in general, they have a positive or negative relationship.

Wavelength and Wave Speed

The waves measured during this time storm at the buoy during this time are called deep-water waves meaning the waves do not ‘feel’ the bottom because the water depth is greater than twice the wavelength. Motion of the water as the wave passes by does not reach to the seafloor so there is no movement of sand or disturbance to benthic organisms.

Recall that surface waves transmit energy on the ocean surface. Waves are typically characterized by their wave height, wave period, and wavelength. They travel from where they are generated (e.g., at the storm) to other areas. All waves travel at different speed based on their wavelength.

  • The wavelength (L) is calculated using: L = gT2/2π, where g=9.8 m/s2 and T is wave period in seconds.
  • The wave phase speed is calculated by the wavelength divided by wave period (just like the speed of your car is distance divided by time): speed = L/T

 


 

Application Questions:

In the questions below, calculate the wavelength and wave phase speed for the waves generated during this storm.

  1. Using the equation above, find the wavelength (L) for the waves on January 5, 2018 at 0000 (remember, this was the time period of the largest wave height).
  2. Based on your answer to #4, how fast were the waves traveling?
  3. Explain how the speed of a wave changes with the wavelength.

 

Reflection Question:

  1. This buoy is located 260 km from the coast of New Jersey. Based on the wave speed at the time of maximum wave height it would take about 4.5 hours for these waves to travel from the buoy to the coastline. Does that seem slow or fast to you? Explain your answer.