Waves Exercise
Q1: Swell prediction
- If a storm sets up in the Gulf of Alaska, 4000 km from Tofino, with wind speeds of 24 m/s, how long until surfers can expect good waves? (hint, figure out the wave height from the Beaufort scale, assuming a well-developed sea, use the ratio of height to wavelength to figure out the wavelength).
- What will the period of these deep-water waves most likely be?
- Those are pretty decent waves. They would be even better if they were 15-s waves. How fast would the wind need to be? - Suppose the 24 m/s waves are travelling, and gradually move from 4000 m of ocean to 20 m. What would you expect the wave height to be (assume they become “shallow-water” waves, and that they don’t change their frequency). Hint: Conserve wave energy into the shallow water. - try to explain why waves that start in the gulf of Alaska often do not have such large amplitudes when they reach our shores?
Q2: Refractions
Consider the bathymetry in the first plot below. If the waves approach from the south, where would you expect the strongest waves to be? Sketch lines of wavecrests.
Q3 More swell prediction
Describe the last plot below. Where are the waves coming from, and what is their period? Briefly explain the patterns of green, blue and cyan. Why does the blue change back to cyan?
