The sun emits energy across a wide spectrum of wavelengths. The portion that reaches Earth’s atmosphere and surface is solar radiation. It includes ultraviolet, visible, and near-infrared light.

About 30 percent of the incoming solar radiation is reflected back to space by clouds, atmosphere, and surface. The remainder is absorbed, warming the planet and driving the atmospheric and oceanic circulations. The amount of solar radiation at the top of the atmosphere varies slightly with solar activity and with Earth’s orbital cycles.

At the surface the intensity depends on latitude, season, time of day, cloud cover, and atmospheric clarity. Solar radiation measurements support climate studies, solar-energy applications, and agricultural planning. Instruments such as pyranometers quantify the incoming energy.

Without solar radiation, Earth’s climate and nearly all surface energy processes would cease.