Question: Seasonal variability is a characteristic feature of Earth. Explain the factors responsible for occurrence of seasonal variations.

Answer: A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. Earth’s seasons are divided into Spring, Summer, Autumn and Winter. However there are additional seasons in different parts of the world such as Monsoon.

Factors responsible for seasonal variations

• Rotation of Earth
  The Earth rotates on its axis during its revolution around the Sun. During rotation, different parts of the Earth are exposed to sunlight during different time. This plays a major role in formation of seasons.
• Eccentricity
  Earth is in shape of geoid with a characteristic bulge at the equator and flat surface at the poles. This ensures that Sun’s rays are not uniform across the globe, causing changes in weather.
• Tilt
  Earth is tilted with an angle of 23.5 degrees on its axis. Due to its tilt, the northern hemisphere and southern hemisphere face the sun alternatively. This causes varying seasons in different hemispheres.
• Perihelion and aphelion
  During revolution around the Sun, Earth will have extreme temperatures during its distance from the Sun. During perihelion ( nearest to Sun) the temperature will be higher and aphelion ( farthest from Sun) it will be lower.

Other reasons

• Pressure belts
  The shifting of pressure belts occurs during various times of the year that brings in seasonal changes.
• Ocean currents
  Ocean currents are responsible for bringing monsoon or winters due to their effects on wind system and temperature.