The global heat budget describes the balance between incoming solar (short-wave) radiation and outgoing terrestrial (long-wave) radiation. These points summarize how this relationship works:
- The Earth absorbs energy from the Sun (insolation - measured by Watts per square metre) and re-radiates it back into the atmosphere. This terrestrial radiation is what we feel as heat.
- The angle of incidence at the Equator is 90 degrees, therefore, this area experiences a heat surplus.
- At higher latitudes, especially at the poles, the Sun's rays approach at a lower angle and are forced to spread out over a larger area. This creates a heat deficit.
- There is also a net loss of radiation throughout the atmosphere, as air cools on rising from the Earth's surface.
- Heat is re-distributed over the Earth by two main mechanisms of heat transfer: vertical (upwards through the atmosphere) and horizontal (from the tropical latitudes towards the polar latitudes across the Earth's surface).
- Some processes and systems responsible for transferring heat and maintaining the global heat budget are air and ocean currents , conduction, radiation, convection and latent heat transfers.
The image on the left shows the global distribution of incoming solar radiation across latitudes while the diagram on the right shows the vertical distribution of incoming solar radiation through the atmosphere.
Click on the arrow to watch this You Tube video that gives a concise explanation of the global heat budget.
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