EXTRATROPICAL /TEMPERATE CYCLONE
WHAT IS EXTRATROPICAL /TEMPERATE CYCLONE?
- These are known as mid-latitude depressions, frontal depressions and wave cyclones.
- They are related to the mid-latitudinal region between 35° and 65° latitude.
- The direction of movement is from west to east.
- They are more prevalent in the winter seasons.
HOW DOES EXTRATROPICAL CYCLONES FORM?
- The formation of temperate cyclones is explained by the Polar Front theory.
- Warm-humid air from the tropics meets the dry-cold air from the poles and forms a polar front.
- Warm air is pushed up by denser and heavier cold air.
- This interaction air creates instability and a low pressure is created at the center.
- A void is created due to low pressure.
- The surrounding air occupy this void and cyclone is formed.
WHAT IS AN AIR MASS?
- When the air stays over a similar region for a quite longer time, it acquires its characteristics.
- These regions can be the vast ocean surface or plains.
- It is a large body of air having little horizontal variation in temperature and moisture.
WHAT ARE FRONTS?
- When two different air masses meet, the boundary zone between them is called front.
- This process is known as frontogenesis.
- There are four types of fronts:
- Stationary: When the front remains stationary.
- Warm: When the warm air mass moves towards the cold air mass, the contact zone is a warm front.
- Cold: When the cold air moves towards the warm air mass, the contact zone is a cold front
- Occluded: When an air mass is fully lifted above the land surface, it is an occluded front.