Basics of heat budget
Published on 31 Jan 2025
The Earth's heat budget involves the balance between incoming solar radiation and outgoing terrestrial radiation.
Incoming solar radiation (Insolation): The Sun emits energy, reaching Earth as solar radiation, mostly in the form of visible light.
Reflection and Scattering: About 35% of incoming solar radiation is reflected back by clouds, atmospheric particles, and Earth's surface.
Absorption: The Earth's surface and atmosphere absorbs the remaining 65% of incoming solar radiation, warming the planet.
Outgoing terrestrial radiation: The Earth emits energy back into space as longer-wavelength infrared radiation due to its warmed surface.
Greenhouse effect: Greenhouse gases (water vapour, carbon dioxide) absorb and re-emit some outgoing infrared radiation, trapping heat in the atmosphere.
Energy balance: Equilibrium occurs when incoming solar radiation equals outgoing terrestrial radiation, maintaining Earth's temperature and climate.
Factors affecting distribution of temperature
Latitude: The Sun's rays are more concentrated near the equator, resulting in higher temperatures, while they are spread over a larger area near the poles, leading to lower temperatures.
Example: Cities near the equator, like Quito in Ecuador, experience relatively high temperatures throughout the year.
Altitude: As elevation increases, temperature decreases. At higher altitudes, the atmosphere is less dense, and there is less air to retain and transfer heat.
Example: La Paz in Bolivia, situated at a high altitude, has lower temperatures than cities at similar latitudes at lower elevations.
Ocean currents: Warm Ocean currents raise temperatures in coastal areas, while cold currents can cool nearby regions.
Example: The North Atlantic Drift warms the climate of Western Europe.
Proximity to water bodies: Coastal areas experience milder temperatures compared to inland regions due to moderating effect.
Example: San Francisco, located near the Pacific Ocean, experiences milder temperatures compared to inland areas.
Wind patterns: onshore wind leading to moist and milder temperature whereas onshore winds are dry leading to temperature extremes.
Example: The Mediterranean climate is influenced by the prevailing westerlies. Cities like Athens, Greece, benefit from westerly winds, experiencing mild, wet winters and hot, dry summers.
Cloud cover: Clouds can reflect sunlight, reducing daytime temperatures, and trap heat, increasing night-time temperatures.
Example: In deserts like the Sahara, where there is often clear sky, temperatures can vary widely between day and night.
Land water distribution: land have lower heat capacity than water thus absorbs more energy. Thus areas with high distribution of land will have higher temperature ranges with extremely warmer and cooler conditions in summer and winter respectively.
Example: Gobi Desert exemplifies continentality with high temperature ranges.