What is Insolation?

What is insolation?

Insolation can be defined as the ‘incoming solar radiation’ on the earth surface.

It is estimated that approx. 1.94 calories reach the top of earth’s atmosphere per square centimeter per minute, which is called Solar Constant.  

The following factors affect it:

• Solar Activity and Sun Spots
• The main change in the Sun is an 11-year solar cycle of high and low activity
• Sunspots are caused by the disturbances in the Sun’s magnetic field rising up to the sun’s visible surface
• Perihelion and Aphelion

When orbiting around the Sun, the position of the earth when it observes greatest distance from it is identified as aphelion and when it is shortest, it is identified as perihelion. This distance of earth from the sun affects the insolation i.e., the annual insolation received by the earth when it is nearest to the sun is slightly greater than what it receives when it is farthest from the sun.

Rotation and Tilt of the Earth

The rotation and degree of tilt also has a great influence on the insolation as the amount of insolation received differs with changes in latitudes and seasons.

Angle and Area of Incidence

The intensity of insolation decreases when the angle decreases with an increase in altitude. A smaller angle leads to slanted rays. Similarly, the intensity of insolation increases as the angle of isolation gets closer to 90 degrees.

Atmospheric Composition

The more the transparency in the atmosphere, the greater the amount of insolation reaches and vice versa. This happens due to more reflection, absorption and diffusion etc. due to the particles like clouds, water vapor, ash and dust particles.