Lecture on Tidal Patterns

Introduction to Tidal Patterns

• Overview of tidal patterns around the world
• Importance of understanding different tidal patterns

Types of Tidal Patterns

1. Diurnal Tides

• Definition: One high tide and one low tide per tidal day
• Example Location: Gulf of Mexico
• Characteristics:
  • One high tide and one low tide every 24 hours and 50 minutes

2. Semi-diurnal Tides

• Definition: Two high tides and two low tides per tidal day, with similar heights
• Example Locations:
  • East Coast of the United States
  • Central and South America
  • Africa
  • New Zealand
• Characteristics:
  • Successive high and low tides have similar heights

3. Mixed Tides

• Definition: Two high tides and two low tides per tidal day, with varying heights
• Example Locations:
  • West Coast of the United States
• Characteristics:
  • Successive high and low tides have different heights

Understanding Tidal Graphs

• Y-Axis: Represents the height of the tide
• X-Axis: Represents time (24-hour scale plus 50 minutes for lunar orbit lag)

Key Concepts

• Mean Lower Low Water: Chosen as the zero point for measuring tides; average of all low tides in a year
• Negative Tides: Occur when the tide is lower than the mean lower low water

Tidal Range Comparisons

Example Analysis: Alaska vs. San Diego

• Alaska:
  • Tidal range up to 19 feet, extending to negative 3.9 feet
  • Overall range up to 25-30 feet
• San Diego:
  • Tidal range from about 7-9 feet

Tidal Range and Lunar Phases

• Spring Tides: Largest tidal ranges during new or full moons when the Earth, moon, and sun are aligned
• Example calculation of tidal range during different lunar phases

Evaluation of Tidal Type

Understanding Semi-diurnal Tides

• Semi-diurnal: Two nearly equal high and low tides each day

Practice Question

• Question: Characteristics of a semi-diurnal tide?
  • Correct Answer: Two nearly equal high and low tides each day

Conclusion

• Recap of tidal patterns: Mixed, Semi-diurnal, Diurnal
• Locations associated with each tidal pattern
• Encouragement to review slides and materials for further understanding

These notes provide a summary of the key points about tidal patterns, including definitions, characteristics, and example locations. Understanding these concepts is essential for comprehending global tidal behaviors and their implications.