Insolation refers to solar radiation.

Insolation is the amount of solar radiation received on the Earth's surface. It is the primary source of energy for various natural processes on our planet. The term "insolation" is derived from the words "incoming solar radiation."

Key Points:
- Solar radiation: Insolation refers to the solar radiation that reaches the Earth's surface. It includes both direct and indirect radiation from the Sun. Solar radiation is made up of electromagnetic waves, including visible light, infrared radiation, and ultraviolet radiation.
- Importance: Insolation is crucial for various natural processes on Earth. It provides energy for photosynthesis in plants, which is the basis of the food chain. It also drives weather patterns, ocean currents, and the water cycle.
- Measurement: Insolation is measured in watts per square meter (W/m²). Instruments called pyranometers are used to measure the amount of solar radiation received at a particular location.
- Factors affecting insolation: Several factors influence the amount of insolation received at a specific location. These include the angle of the Sun's rays, atmospheric conditions, cloud cover, and the Earth's rotation and tilt.
- Seasonal variation: Insolation varies throughout the year due to the Earth's tilt on its axis. This variation is responsible for the changing seasons. During summer, when a particular hemisphere is tilted towards the Sun, the insolation is more intense, resulting in warmer temperatures. In winter, when the hemisphere is tilted away from the Sun, the insolation is less intense, leading to colder temperatures.
- Distribution: Insolation is not evenly distributed across the Earth's surface. The equatorial regions receive the highest amount of insolation, while the polar regions receive much less. This uneven distribution affects global climate patterns.
- Influence on climate: Insolation plays a significant role in determining regional and global climate patterns. It influences temperature gradients, atmospheric circulation, and the formation of weather systems such as high and low-pressure systems. Variations in insolation are responsible for long-term climate changes, including ice ages and interglacial periods.

In conclusion, insolation refers to solar radiation, which is the primary source of energy for various natural processes on Earth. It is measured in watts per square meter and varies throughout the year due to factors such as the Earth's tilt and atmospheric conditions. Insolation plays a crucial role in climate patterns and is essential for sustaining life on our planet.