Seasons notes

Introduction

  • Focus on the driving forces behind seasons and concepts surrounding climate controls.

  • Some students may believe they already understand these concepts from past education, but internalization and application remain key challenges.

Major Climatic Controls

  • Important for understanding climate variations.

1. Land vs. Water

  • Key Concept: Proximity to land or water influences temperature.

  • Example: In summer, areas near lakes are cooler. In winter, they are warmer due to lake temperatures averaging around 38 degrees Fahrenheit (approx. 3 degrees Celsius).

2. Atmospheric Circulation

  • Refers to wind movement and its influence on climatic conditions.

  • Example: Different wind patterns lead to varying climates between places like Wyoming and Minnesota.

3. Ocean Currents

  • Work in tandem with atmospheric circulation, significantly impacting regional climates.

  • Example: Sweden, despite being at a similar latitude to colder regions, experiences milder climates due to ocean currents.

4. Terrain Features

  • Plays a role in local climate variations.

  • Example: Hiking along beach areas may reveal pockets of warmer air due to terrain shapes influencing air circulation.

5. Local Features

  • Urban heat islands: Cities tend to be warmer because of materials that absorb and retain heat.

  • Example: Concrete surfaces in cities during the day absorb sunlight and release it as heat.

6. Human Impact

  • Humans introduce heat into the atmosphere through various activities and enhance greenhouse effects.

  • Examples: Burning fossil fuels (coal, oil, natural gas), agriculture changes, and carbon dioxide release vs. carbon uptake by plants.

7. Greenhouse Gases and Carbon Dioxide

  • Carbon dioxide is a key greenhouse gas.

  • Continuous release and uptake balance occur through biological processes involving plants.

  • Example: Human activities lead to increased levels of carbon dioxide in the atmosphere compared to natural processes.

Effects of Seasons

  • Solar Radiation: Sunlight is essential for setting circadian rhythms and mental health.

    • Recommendation: 10 minutes of daily sun exposure without sunscreen for Vitamin D intake.

Earth's Motion

  • Rotation: Earth rotates every 24 hours (23 hours, 56 minutes, and 4 seconds). This rotation influences night and day.

    • Causes seasonal variations but isn't directly responsible for temperature differences.

  • Revolution: Earth revolves around the sun in an elliptical orbit.

    • Aphelion: The farthest point from the sun around July 3rd (approx. 152,000,000 kilometers away).

    • Perihelion: The closest point to the sun around January 3rd (approx. 147,000,000 kilometers away).

    • Misconception: Seasons are not caused by distance to the sun.

Key Misconceptions

  • Many believe seasons relate to proximity to the sun rather than the axial tilt of the Earth, which is around 23.5 degrees.

Axial Tilt and Its Importance

  • The 23.5-degree tilt creates variation in sunlight and seasonal differences.

  • Sun Angle: Direct sunlight leads to warmer temperatures, while angled sunlight spreads energy out, leading to cooler temperatures.

Solar Angle Calculation

  • Formula: 90^ ext{o} - ext{latitude distance from subsolar point}

  • The subsolar point is the location where the sun is directly overhead at noon.

Seasonal Changes

  • Equinoxes: Times of equal day and night length.

    • Vernal Equinox: Around March 21st, beginning of spring.

    • Autumnal Equinox: Around September 22nd, beginning of fall.

Solstices

  • Winter Solstice: Around December 21st, shortest day of the year in the northern hemisphere.

  • Summer Solstice: Around June 21st, longest day of the year in the northern hemisphere.

Equatorial vs. Polar Regions

  • Equator: Experiences consistent seasons, little variation year-round.

  • Polar Regions: Extreme variations between summer and winter due to tilt and sunlight angles.

Example Locations' Seasonal Differences

  • Winnipeg: Solar angle in December is 16.5 degrees; receives 7.44 megajoules per meter squared of radiation.

  • Austin: Solar angle of 36.5 degrees; receives 12.18 megajoules per meter squared of radiation.

  • Seasonal day length differences are appreciable.

Summary of Seasonal Drivers

  • Importance of axial tilt and solar angle in determining seasonal variations.

  • Understanding how rotation and revolution impact local climates and seasonal patterns.

Implications for Future Study

  • Recognizing how climate controls interplay with human activities and environmental outcomes.

  • Preparing for tests/assessments focused on these core concepts.