Question:
Examine the concept of air masses and fronts. Explain how far fronts contribute to the formation of cyclones. ( BPSC, 2019)
Answer:
Air masses are the large body of air with nearly uniform physical characteristics such as temperature, moisture. Due to the different densities of neighboring air masses, they do not mix easily with each other. Hence, there are some special weather phenomena at the convergence zone or boundary zone of two air masses and which are called fronts.
Concept of air masses and fronts:
Before going to discuss the concept of air masses. we need to first understand the types of air masses.
On the basis of temperature, there are two types of air masses:
Cold Air mass:
When the air mass is colder than the surface over it. A cold air mass is relatively unstable as land is warmer and air rises after heating and creat instability. Cold air masses contribute to the formation of cyclones.
Warm Air mass:
When the air mass is warmer than the surface over it, is called warm air mass. It creates stability in the atmosphere and anti-cyclonic atmospheric conditions.
On the basis of moisture, there are two types of air masses:
- Continental air masses
- Oceanic air masses
Oceanic air masses are moist and cause rainfall.
Monsoon rainfall in India is the result of the shifting of oceanic air masses toward the Indian subcontinents.
Interaction between the two different air masses often causes instability in the atmosphere and causes bad weather.
Fronts contribute to the formation of cyclones:
- Cyclones are violent storms or inward air circulation around the low-pressure areas that create bad weather.
- The polar Front theory explains the origin and development of temperate cyclones or extratropical cyclones.
- As per the theory, the polar front is formed at the meeting line of warm humid air masses from tropics and dry cold air masses from poles.
- At the polar front low pressure is created where humid air mass and dry cold air mass interacts.
- Warm air masses are pushed up by cold air masses due to the denser and heavier nature of cold air masses.
- As a result, the void is created and surrounding air rushes to occupy these space, and thus extratropical or temperate cyclone is formed.
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