Insolation: Angle of Incidence

Earth is the only planet that sustains life. However, this planet has different temperatures according to the seasons. All of this happens because of the tilted nature of the Earth while revolving around the Sun. This tilt is the reason that explains the varying amounts of solar radiation at various places and different times of the year. 

In a nutshell, insolation is the amount of solar radiation received on the surface of Earth or any planet of the universe. In this article, we will be discussing insolation and its controls. We will also define the variable temperatures on Earth. 

What is Insolation?

The Sun is the primary energy source on Earth and other planets. Earth receives energy from the Sun through short waves known as solar radiation. These solar radiations are the significant source of energy present on Earth. Insolation is defined as the amount of solar radiation that falls on the surface of any planet revolving around the Sun. That is why we see different temperatures in different regions in the same season. 

When solar energy reaches the Earth, some of it is scattered, absorbed, or reflected by the atmosphere. Therefore, only a portion of it reaches the surface. Insolation pertains to the incoming solar radiation that falls on the Earth’s surface and shows heating effects on the Earth’s surface. Several factors affect and influence insolation. 

Factors Affecting Insolation 

The amount of insolation the Earth receives varies everywhere from time to time. The planet’s tropical zone receives the maximum insolation in a year. On the other hand, the insolation gradually decreases as we move towards the poles. The weather becomes summers and winters due to the amount of insolation received. 

The factors that influence the amount of insolation received on the surface of the planet are:

• Day duration
• The angle of incidence
• Clarity and transparency of the atmosphere

Day duration

It varies in different seasons and place to place. For example, the duration of a day decides the amount of insolation the surface of the Earth receives. 

Suppose the day is long. In that case, the amount of insolation received is also high. On the other hand, the insolation received is less if the day’s duration is shorter.

The angle of incidence

The shape of the Earth is round, and the axis is tilted. Due to this round shape, the rays from the Sun strike the surface at different places with different angles. The angle formed by the Sun’s incident ray with the tangent of the Earth’s circle at a point is known as the angle of incidence. 

The angle of incidence influences insolation in two phases. The first phase is a series of two different cases where different angles of incidence have a different effect on the Earth’s surface.

Case -1 

The rays coming from the Sun are vertical when the Sun is almost overhead, and it eventually results in a larger angle of incidence. 

Due to this larger angle of incidence, these sun rays concentrate within a smaller area. This aspect results in an enormous amount of insolation in that particular place.  

Case-2

In this case, when the sun rays have oblique nature, the angle of incidence reduces, resulting in a larger area. This fact leads to a condition when sun rays generate a healing effect on a greater zone. It eventually results in a lower amount of insolation received on this place.

Transparency and clarity of the atmosphere

How clear the atmosphere is, determines and controls the amount of insolation received on the Earth’s surface. 

By the terms clarity and transparency of the atmosphere, we refer to the cloud covering thickness and water vapours and dust particles present in the atmosphere. These factors can have a transmission reflection or absorption effect on insolation. 

The thickness of clouds can reflect the solar radiation, while thin clouds transmit it. At the same time, a cloudless sky allows it to reach the surface without any hindrance. The water vapour in the atmosphere absorbs insolation and eventually results in fewer sun rays striking the surface.  

What is the Importance of Insolation in Geography?

There is considerable importance of insolation in geography, as it is the deciding factor behind the temperature of a specific place. Insolation is significant because it is the main reason and ultimate source of diversification in climatic conditions of different places at different times.

Conclusion

Insolation directly refers to the unique nature of sun rays on the Earth’s or any other planet’s surface. 

The angle of incidence of insolation is the deciding factor of temperature on the surface. Earth’s tilted axis and round shape contribute to insolation, making it an influential phenomenon in the planet’s climatic conditions, with its dynamic effects. 

Insolation is crucial for supporting life on this planet as everything depends on sunlight.