Understanding Ocean Waves

Key Concepts

• Wavelength (L): The distance between consecutive crests of a wave.
• Wave Base: Equal to half the wavelength; depth at which the orbital motion of waves feels friction with the ocean bottom.
• Deep Water vs Shallow Water Waves:
  • Deep Water Wave: Occurs when the wave base is less than the depth of the water.
  • Shallow Water Wave: Occurs when the wave base is greater than the depth of the water.

Example Problem

• Given:
  • Wavelength (L) = 50 meters
  • Ocean Depth = 30 meters
  • Wave Base = 25 meters (half of wavelength)
• Conclusion: The wave base (25 meters) is less than the ocean depth (30 meters), indicating a deep water wave.

Oceanography Wave Concepts

• Wave Height: Vertical distance from the wave trough to the wave crest.
• Wavelength: Horizontal distance between two consecutive wave crests.
• Wave Period: Time between two successive wave crests.
  • Typical wave periods: 12-15 seconds in Southern California.

Graph Analysis

• Wave Period, Wavelength, and Wave Speed Relationship:

  • Longer wave periods correlate with longer wavelengths and faster speeds.
  • Graphs can help determine wave speed and wavelength based on wave period measurements.

• Wave Dispersion:

  • Processes by which waves separate according to speed, period, and wavelength as they travel.
  • Results in uniform ocean swells.

Wave Base and Interaction with Bottom

• Wave Base Calculation: Depth at which waves start feeling bottom friction equals half the wavelength.
• Changes in Shallow Water:
  • Wave velocity and wavelength decrease as waves move into shallower water.
  • Wave height increases as energy is pushed upward.
  • Wave period remains constant despite changes in velocity and wavelength.

Practical Exercise

• Graph Interpretation:
  • Relating wind speed to wavelength formation.
  • Example: A 150-meter wavelength is formed by 42 knots wind.

Important Figures

• Familiarize yourself with graphs showing relationships between wave attributes and wind conditions.

Additional Study

• Review provided worksheet and lecture material.
• Anticipate similar questions on exams concerning wave dynamics and characteristics.