Overview
This lecture reviews key factors affecting the amount of solar energy (insolation) received at Earth’s surface, focusing on latitude, seasons, and the differences between land and sea. It prepares you for the upcoming test.
Factors Affecting Insolation
- Insolation is incoming solar radiation that heats the Earth's surface and air above.
- The angle of the Sun varies with latitude: higher at the equator, lower at higher latitudes.
- At the equator, a large angle concentrates energy on a small area, resulting in more heat per unit land.
- At high latitudes, a small Sun angle spreads energy over a larger area, leading to less heat per unit.
- Insolation travels a shorter distance through the atmosphere at low latitudes, leading to less energy loss.
- Higher latitudes have more atmospheric distance, increasing reflection, absorption, and scattering.
Seasonal and Latitudinal Variations
- The tilt of Earth’s axis (23.5°) and revolution around the Sun cause seasons.
- The overhead Sun shifts between the Tropic of Cancer (June solstice) and Tropic of Capricorn (December solstice).
- At solstices and equinoxes, the angle and duration of sunlight change, altering insolation.
- Daylight duration increases with latitude, especially in summer (up to 24 hours in the Arctic Circle).
Comparing Land and Sea (Continentality)
- Land heats and cools more quickly due to lower specific heat capacity.
- The sea heats and cools slowly, modifying coastal air temperatures.
- Coastal areas have smaller annual temperature ranges and milder climates (maritime climate).
- Inland areas have larger temperature ranges with hotter summers and colder winters (continental climate).
Surface Reflection (Albedo Effect)
- Light-colored surfaces reflect more solar energy, dark surfaces absorb more.
- Snow and sand have high albedo (reflection), while forests and dark soils have low albedo (absorption).
Measuring and Describing Temperature
- Mean temperature: average of the highest and lowest temperatures.
- Annual range: difference between the highest and lowest monthly mean temperatures.
- Isofims (isotherms): lines joining places with the same temperature on a map.
- Equatorial regions have small temperature ranges; higher latitudes have larger ranges.
Key Terms & Definitions
- Insolation — Incoming solar radiation reaching Earth’s surface.
- Angle of the Sun — The angle at which sunlight strikes the Earth, influencing energy concentration.
- Overhead Sun — When the Sun is directly above, forming a 90° angle with the ground.
- Latitude — Measurement north or south of the equator, affecting insolation.
- Albedo — The ratio of reflected to incoming solar radiation.
- Continentality — Climate effect due to distance from the sea.
- Isofim/Isotherm — Line on a map joining locations of equal temperature.
- Annual range of temperature — The difference between the highest and lowest annual mean temperatures.
Action Items / Next Steps
- Review textbook pages 3 and 6 regarding insolation, angle of the Sun, and atmospheric impact.
- Prepare notes, diagrams, and summary tables for test revision.
- Watch the posted video and review uploaded diagrams on Google Classroom.
- Understand key terms and be able to describe temperature trends using correct terminology.