Solar Radiation: Definition and Meaning

Study Notes

Solar radiation refers to electromagnetic waves emitted from the Sun.
Types of solar radiation include visible light, infrared light, and ultraviolet light.
The term "radiation" in this context does not have negative connotations as seen in nuclear contexts.

Solar irradiance measures the energy from the Sun received by the Earth.
Units of measurement include watts per square meter (W/m²) and kilowatt hours per square meter (kWh/m²).
Solar irradiance varies seasonally and is mapped to show energy absorption across different regions.

The electromagnetic spectrum consists of various types of radiation, ordered by frequency: radio waves, microwaves, infrared, visible, ultraviolet, X-rays, and gamma rays.
Incoming solar radiation is absorbed by Earth’s atmosphere and surface, primarily in the form of infrared, visible, and ultraviolet light.

Visible light, detectable by the human eye, spans wavelengths from approximately 400 to 750 nanometers.
The spectrum of visible light includes red (around 700 nm), orange (600 nm), yellow (550 nm), green (500 nm), blue (450 nm), indigo, and violet (just below 400 nm).

Infrared light ranges from 750 nm to 2.5 micrometers, and is invisible to the human eye but detectable through its warmth.
It plays a critical role in warming the planet.

Ultraviolet (UV) light has wavelengths between 1 nm and 400 nm.
UV-A light (above 300 nm) is generally harmless, while UV-B and UV-C (below 300 nm) are harmful and can damage human cells.

Incoming solar radiation is crucial for maintaining Earth's temperature and supports life by driving the water cycle and weather systems.
Earth's climate is influenced by the tilt of its axis rather than just distance from the Sun. This tilt creates seasonal variations in sunlight intensity.
The greenhouse effect occurs when outgoing infrared radiation is partially absorbed by the atmosphere, trapping heat and potentially leading to global warming.
Human-induced changes to atmospheric chemistry have exacerbated the greenhouse effect, leading to increased temperatures.