Q1. Which of the following statements best explains the initial trigger for cyclogenesis in temperate regions?
A. Intense surface heating over continents
B. Convergence of trade winds near ITCZ
C. Interaction of contrasting air masses
D. Orographic uplift due to mountain barriers
Answer: C
Explanation:
- Polar Front Theory (Bjerknes Model):
- Cyclogenesis originates at the polar front, where warm, moist tropical air meets cold, dense polar air.
- This boundary is a zone of strong horizontal temperature gradient (baroclinic zone) → inherent instability.
- Mechanism:
- Cold air undercuts warm air → forced uplift → pressure falls locally.
- Leads to wave formation along the front → cyclonic circulation initiated.
Q2.
Assertion (A): Temperate cyclones are associated with frontal systems.
Reason (R): They develop due to horizontal temperature contrasts between air masses.
A. Both A and R are correct and R explains A
B. Both A and R are correct but R does not explain A
C. A is correct but R is incorrect
D. A is incorrect but R is correct
Answer: A
Explanation:
- Assertion Validity:
- Temperate cyclones are also called frontal cyclones → always associated with warm and cold fronts.
- Reason Validity:
- Formation driven by horizontal thermal gradient (baroclinicity) between air masses.
- Linkage:
- Temperature contrast → creates fronts → fronts evolve into cyclonic disturbances.
Q3. Consider the following statements regarding temperate cyclones:
- They are symmetrical systems with circular isobars.
- Warm sector lies between warm and cold fronts.
- Occlusion occurs when the warm front overtakes the cold front.
- They derive energy mainly from latent heat release.
Which of the above are correct?
A. 2 only
B. 2 and 3 only
C. 1, 3 and 4 only
D. 2, 3 and 4 only
Answer: A
Explanation:
- Statement 1: Incorrect
- Temperate cyclones are asymmetrical (inverted ‘V’ shape) due to unequal distribution of air masses.
- Statement 2: Correct
- Warm sector = wedge of warm air between advancing warm front and trailing cold front.
- Statement 3: Incorrect
- Cold front overtakes warm front, not vice versa → leads to occlusion stage.
- Statement 4: Incorrect
- Primary energy source = horizontal temperature gradient (baroclinic energy).
- Latent heat → secondary role, unlike tropical cyclones (where it is dominant).
Q4. Match the Following (Process-Based Understanding)
| List I (Front) | List II (Weather) |
| 1. Warm Front | A. Cumulonimbus clouds, intense rainfall |
| 2. Cold Front | B. Gradual cloud formation, steady precipitation |
| 3. Occluded Front | C. Dissipation stage of cyclone |
Select the correct answer:
A. 1-B, 2-A, 3-C
B. 1-A, 2-B, 3-C
C. 1-B, 2-C, 3-A
D. 1-C, 2-A, 3-B
Answer: A
Explanation:
- Warm Front (1-B):
- Gentle slope → gradual uplift of warm air over cold air
- Cloud sequence: Cirrus → Cirrostratus → Altostratus → Nimbostratus
- Results in prolonged, steady rainfall
- Cold Front (2-A):
- Steep slope → rapid uplift
- Leads to cumulonimbus clouds → heavy rainfall, thunderstorms
- Occluded Front (3-C):
- Cold front overtakes warm front → warm air lifted completely
- Marks mature/decay stage → weakening cyclone
Q5. Western Disturbances affecting North-West India are:
A. Tropical cyclones originating in Bay of Bengal
B. Temperate cyclones originating in Mediterranean region
C. Local convectional storms
D. Monsoonal low-pressure systems
Answer: B
Explanation:
- Definition:
- Western Disturbances = eastward-moving extra-tropical cyclones embedded in subtropical westerly jet stream.
- Source Region:
- Originate over Mediterranean Sea / West Asia → move towards India.
- Mechanism:
- Travel along westerlies (jet streams) → bring moisture from Mediterranean/Caspian regions.
- Importance:
- Provide winter rainfall in North-West India → critical for Rabi crops (wheat, mustard).
- Also responsible for snowfall in Himalayas → glacier nourishment.
