Sunlight falls almost vertically on the equator, while it falls at slanting angle on the poles. Due to this, amount of insolation decreases from equator towards poles.

Amount of Insolation Decreases from Equator Towards Poles

Insolation, or incoming solar radiation, refers to the amount of solar energy received per unit area on the Earth's surface. It is influenced by various factors, including the angle at which the sunlight reaches the Earth, the length of daylight, and the distance the sunlight has to travel through the atmosphere. As we move from the equator towards the poles, the amount of insolation decreases. This phenomenon can be explained by several factors:

1. Angle of Incidence:
The angle at which sunlight reaches the Earth's surface plays a crucial role in determining the amount of insolation received. Near the equator, the sun's rays are almost perpendicular to the surface, resulting in more concentrated and intense solar radiation. However, as we move towards the poles, the angle of incidence becomes increasingly oblique. Consequently, the same amount of solar energy is spread over a larger surface area, leading to a decrease in insolation.

2. Atmospheric Path Length:
The distance sunlight has to travel through the Earth's atmosphere before reaching the surface also affects the amount of insolation received. Near the equator, the atmosphere is relatively thinner, allowing more solar energy to reach the surface. However, as we move towards the poles, sunlight has to pass through a greater thickness of the atmosphere. This increased path length results in greater scattering and absorption of solar radiation by atmospheric particles and gases, leading to a reduction in insolation.

3. Daylight Duration:
The length of daylight, or the number of hours the sun is above the horizon, varies with latitude. Near the equator, the duration of daylight is relatively consistent throughout the year, resulting in a higher total amount of solar radiation received over time. However, as we move towards the poles, the length of daylight progressively decreases, leading to a reduction in the total amount of insolation received.

4. Albedo:
Albedo refers to the reflectivity of a surface. Different regions of the Earth have varying albedo values, with lighter surfaces reflecting more sunlight back into space and darker surfaces absorbing more solar radiation. Near the equator, there is a higher prevalence of darker surfaces such as forests and oceans, which absorb a significant portion of the incoming solar energy. In contrast, as we move towards the poles, lighter surfaces such as ice and snow become more prevalent, resulting in a higher albedo and a decrease in the amount of insolation absorbed by the Earth's surface.

In conclusion, the amount of insolation decreases from the equator towards the poles due to factors such as the angle of incidence, atmospheric path length, daylight duration, and surface albedo. These factors combine to distribute the same amount of solar energy over a larger surface area, leading to a decrease in the intensity and total amount of insolation received at higher latitudes.

Amount if insolation is highest at equator because light falls exactly vertically to it and whereas light becomes slanting when it goes to polar region. That's why polar region gets less heat